Exomorfolog A
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Transcript of Exomorfolog A
![Page 1: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/1.jpg)
Reino Plantae
Ang
iosp
erm
as
Plantas con semilla
Plantas vasculares
![Page 2: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/2.jpg)
Morfología de Angiospermas
![Page 3: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/3.jpg)
Figure 35.2
Reproductive shoot (flower)
Terminal bud
Node
Internode
Terminalbud
Vegetativeshoot
BladePetiole
Stem
Leaf
Taproot
Lateral roots Rootsystem
Shootsystem
Axillarybud
Sistema caulinaro vástago
Sistema radicularRaiz lateral
Raíz principal
TalloYema auxiliar
PecíoloLáminaHoja
Rama vegetativa
Yema terminal
Entrenudo
Nudo
Rama vegetativa
Yema terminal
Rama florífera
![Page 4: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/4.jpg)
Al formarse la plúmula y la radícula se establece una bipolaridad que permanecerá determinando el desarrollo posterior de la planta.
Al germinar la semilla se activan los meristemaapicales del tallo y la raíz de la plántula.
EMBRIÓN
Los órganos comienzan a desarrollarse y a partir de allí se irán destacando las estructuras específicas de los órganos fundamentales
![Page 5: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/5.jpg)
Crecimiento primario del vástago
• Meristema apical del vástago– Masa en forma de domo de células en estado de división en la
porción apical del tallo– Forma entrenudos y nudos que portan hojas
Apical meristem Leaf primordia
Developingvascularstrand
Meristema apical Primordio foliar
![Page 6: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/6.jpg)
Yemas múltiples
Colaterales Lineales
![Page 7: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/7.jpg)
Yema apical y axilar en monocotiledónea
Yema auxiliar
Base foliar
Ápice del vástago
Primordio foliar Tallo
Tallo
![Page 8: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/8.jpg)
Macroblastocrec. Indef.
Braquiblasto crec. Def.
![Page 9: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/9.jpg)
Yemas escamosas.Yemas desnudas
Yemas adventiciasKalanchoe
![Page 10: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/10.jpg)
En árboles caducifolios, los nudos quedan marcados por las cicatrices foliares
![Page 11: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/11.jpg)
Crecimiento primario del vástago
• Meristema apical del vástago– Masa en forma de domo de células en estado de división en la
porción apical del tallo– Forma entrenudos y nudos que portan hojas
Apical meristem Leaf primordia
Developingvascularstrand
Meristema apical Primordio foliar
![Page 12: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/12.jpg)
![Page 13: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/13.jpg)
RAMIFICACIRAMIFICACIÓÓN DEL VN DEL VÁÁSTAGOSTAGO
DICOTÓMICA LATERAL
![Page 14: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/14.jpg)
DICOTDICOTÓÓMICAMICAISOTÓMICO
ANISOTÓMICO
las dos ramas tienen igual vigor
cuando las dos ramas hijas tienen distinto vigor
2. La presencia de ramas no está relacionada con la posición de la hoja
1. Las ramas se originan en la yema terminal
REGLAS
![Page 15: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/15.jpg)
RamificaciRamificacióón lateraln lateral
Se forma por actividad de las yemas axilares.
Hoja axilante o tectriz: es la que lleva en su axila una rama
REGLAS
Las ramas se originan en yemas laterales
La posición de las ramas está estrechamente relacionadas con la de las hojas
![Page 16: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/16.jpg)
1-Plantas policárpicas o perennesperenne herbáceaperennes leñosas
2-Plantas monocárpicas
• Anuales• bienales• pluriennales
![Page 17: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/17.jpg)
Plantas monocárpicas
•anuales (arveja, soja, tabaco, zapallo, zapallito), •bienales (zanahoria, cebolla, lechuga, remolacha).•pluriennalesAgavespp. Phyllostachys bambusoide (120 años) o Fourcroya gigantea, Agavaceae(400 años).
![Page 18: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/18.jpg)
monopodialmonopodial
SimpodialSimpodial
monocasiomonocasio
SimpodialSimpodial
dicasiodicasio
MONOPODIAL SIMPODIAL
SISTEMAS DE CRECIMIENTOSISTEMAS DE CRECIMIENTO
![Page 19: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/19.jpg)
SIMPODIAL MONOCASIO
SIMPODIALDICASIO
SIMPODIALPLEOCASIO
Cuando las ramas provienen de tres o más yemas laterales del mismo nudo
![Page 20: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/20.jpg)
Las mejores soluciones del diseño industrial ya las ha anticipado la Naturaleza
• Blossfeldt (1865-1932)
![Page 21: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/21.jpg)
Hoja dicotiledónea
![Page 22: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/22.jpg)
Hoja dicotiledónea
![Page 23: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/23.jpg)
Tipos de nerviación
![Page 24: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/24.jpg)
Hoja dicotiledónea
![Page 25: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/25.jpg)
Hoja dicotiledónea
![Page 26: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/26.jpg)
Hoja dicotiledónea
![Page 27: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/27.jpg)
Hoja dicotiledónea:
![Page 28: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/28.jpg)
Hoja dicotiledónea:Sucesión foliar
![Page 29: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/29.jpg)
Hoja monocotiledónea
![Page 30: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/30.jpg)
Hoja monocotiledónea
Cebolla
CamaloteSagitaria
![Page 31: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/31.jpg)
Hoja monocotiledónea
PalmeraAchira
![Page 32: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/32.jpg)
Filotaxis Verticilada
Dispersa
![Page 33: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/33.jpg)
REGLAS DE LA FILOTAXIS
EQUIDISTANCIA
ALTERNANCIA
Las hojas se ordenan a lo largo de la espiral generatriz con un ángulo de divergencia característico
Este ángulo es menor de 180° y se expresa como fracciones de circunferencia
1/2, 1/3, 2/5, 3/8, 5/13... 180°, 120°, 144°, 135°, 138°...
La serie está constituida por elementos en los que tanto el numerador como el denominador son iguales a la suma de los de los dos términos anteriores:
Fibonacci (Pisa, s. XII-XIII)
y converge hacia 137° 30' 28’’
![Page 34: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/34.jpg)
Filotaxis
![Page 35: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/35.jpg)
Filotaxis
dística
![Page 36: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/36.jpg)
Filotaxis
espiralada
![Page 37: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/37.jpg)
![Page 38: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/38.jpg)
![Page 39: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/39.jpg)
![Page 40: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/40.jpg)
Raíces
• funciones– Anclaje– Absorción– Almacenamiento
Figure 35.3
Pelos radiculares
![Page 41: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/41.jpg)
RAÍCES ADVENTICIASno se originan a partir de la radícula embrionaria
![Page 42: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/42.jpg)
SISTEMAS RADICALESSISTEMAS RADICALES
SISTEMA ALORRIZO
•Sistema radical primario
•Constituido por la raíz principal y sus ramificaciones laterales
•Dicotiledóneas y Gimnospermas
•Pueden formar raíces adventicias, bajo condiciones especiales
![Page 43: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/43.jpg)
RAÍZ PRIMARIA
RAÍZ LATERAL DE 1ER ORDEN
RAÍZ LATERAL DE 2º ORDEN
RAÍZ LATERAL DE 3ER ORDEN
![Page 44: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/44.jpg)
SISTEMA HOMORRIZO
•Constituido principalmente por raíces adventicias
•Reemplazan totalmente o complementan la función de absorción y sostén
•La raíz principal puede no crecer o hacerlo en grado variable
•Común en Monocotiledóneas, Pteridofitas, Dicotiledóneas herbáceas y algunas leñosas
![Page 45: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/45.jpg)
Zona de diferenciación celular
Zona de elongación celular
Zona de división celular
Cofia o caliptra
![Page 46: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/46.jpg)
Cofia ocaliptra
Capa de mucílago = Mucigel
![Page 47: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/47.jpg)
Adaptaciones a la temperatura
![Page 48: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/48.jpg)
GeófitasAdaptaciones a la temperatura
![Page 49: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/49.jpg)
GeófitasAdaptaciones a la temperatura
![Page 50: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/50.jpg)
tubérculo caulinar (papa)
GeófitasAdaptaciones a la temperatura
![Page 51: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/51.jpg)
zanahoriaremolacha azucareraremolacha
GeófitasAdaptaciones a la temperatura
![Page 52: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/52.jpg)
tubérculo radical
laterales
GeófitasAdaptaciones a la temperatura
![Page 53: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/53.jpg)
GeófitasAdaptaciones a la temperatura
![Page 54: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/54.jpg)
GeófitasAdaptaciones a la temperatura
![Page 55: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/55.jpg)
Adaptaciones al agua
-Poikilohídrica Polypodium squalidum
-homoiohídricas: xerófitas, freatófitas,
![Page 56: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/56.jpg)
Xerófitas: adaptadas a sequía
Espinas caulinares y foliares
![Page 57: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/57.jpg)
Xerófitas: adaptadas a sequíaTallos, ramas o pecíolos aplanados
![Page 58: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/58.jpg)
aguijones
Xerófitas: adaptadas a sequía
![Page 59: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/59.jpg)
Xerófitas: adaptadas a sequía
suculencia
![Page 60: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/60.jpg)
Xerófitas: adaptadas a sequía
![Page 61: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/61.jpg)
• Efímeras
• Boerhavia repens
• (Sahara, 10 días )
![Page 62: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/62.jpg)
•Xerófitas: adaptadas a sequía
Otras adaptaciones:? relación raiz/vástagofreatofitashojas pequeñas con ? relación superficie/volúmenhojas revolutashojas escuamiformeslimbo de perfil a la luz
![Page 63: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/63.jpg)
Hidrófitas. Plantas acuáticas
![Page 64: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/64.jpg)
Hidrófitas. Plantas acuáticas
![Page 65: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/65.jpg)
Hidrófitas. Plantas acuáticas
![Page 66: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/66.jpg)
Hidrófitas. Plantas acuáticas
![Page 67: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/67.jpg)
Hidrófitas. Plantas acuáticas
![Page 68: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/68.jpg)
Hidrófitas. Plantas acuáticas
![Page 69: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/69.jpg)
Hidrófitas. Plantas acuáticas
![Page 70: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/70.jpg)
Hidrófitas. Plantas acuáticas
![Page 71: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/71.jpg)
Adaptaciones al aprovechamiento de la luz
Plantas trepadoras
![Page 72: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/72.jpg)
Adaptaciones al aprovechamiento de la luz
Zarcillos: caulinareso foliares
![Page 73: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/73.jpg)
Adaptaciones al aprovechamiento de la luz
Vitis
![Page 74: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/74.jpg)
Adaptaciones al aprovechamiento de la luz
![Page 75: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/75.jpg)
Tilandsia
Pelos escamosos en hojas
Adaptaciones al aprovechamiento de la luz
![Page 76: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/76.jpg)
Condiciones anormales de nutrición
holoparásita
Cuscutaspp
![Page 77: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/77.jpg)
Condiciones anormales de nutrición
Holoparásita
![Page 78: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/78.jpg)
Condiciones anormales de nutrición
Hemiparásita
haustorio
![Page 79: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/79.jpg)
Condiciones anormales de nutrición
hemiparásitas
![Page 80: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/80.jpg)
Condiciones anormales de nutrición
pneumatóforos
![Page 81: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/81.jpg)
Condiciones anormales de nutrición
![Page 82: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/82.jpg)
Adaptaciones del Cormo
1. Temperatura: geofitas
2. Escasez de agua (+ temperatura) xerofitas
3. Exceso de agua: hidrofitas
4. Poca luz: trepadoras, epifitas
5. Nutrición deficiente: ej. carnívoras,
![Page 83: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/83.jpg)
The Three Tissue Systems: Dermal, Vascular, and Ground
• Each plant organ– Has dermal, vascular, and ground tissues
Figure 35.8
Dermaltissue
Groundtissue Vascular
tissue
![Page 84: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/84.jpg)
• The dermal tissue system– Consists of the epidermis and periderm
![Page 85: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/85.jpg)
• The vascular tissue system– Carries out long-distance transport of
materials between roots and shoots– Consists of two tissues, xylem and phloem
![Page 86: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/86.jpg)
• Xylem– Conveys water and dissolved minerals upward
from roots into the shoots• Phloem
– Transports organic nutrients from where they are made to where they are needed
![Page 87: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/87.jpg)
• Ground tissue– Includes various cells specialized for functions
such as storage, photosynthesis, and support
![Page 88: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/88.jpg)
Common Types of Plant Cells
• Like any multicellular organism– A plant is characterized by cellular
differentiation, the specialization of cells in structure and function
![Page 89: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/89.jpg)
• Some of the major types of plant cells include– Parenchyma– Collenchyma– Sclerenchyma– Water-conducting cells of the xylem– Sugar-conducting cells of the phloem
![Page 90: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/90.jpg)
• Parenchyma, collenchyma, and sclerenchyma cells
Figure 35.9
Parenchyma cells 60 μm
PARENCHYMA CELLS
80 μm Cortical parenchyma cells
COLLENCHYMA CELLS
Collenchyma cells
SCLERENCHYMA CELLS
Cell wall
Sclereid cellsin pear
25 μm
Fiber cells
5 μm
![Page 91: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/91.jpg)
• Water-conducting cells of the xylem and sugar-conducting cells of the phloem
Figure. 35.9
WATER-CONDUCTING CELLS OF THE XYLEM
Vessel Tracheids 100 μm
Tracheids and vessels
Vesselelement
Vessel elements withpartially perforated end walls
Pits
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Companion cell
Sieve-tubemember
Sieve-tube members:longitudinal view
Sieveplate
Nucleus
CytoplasmCompanioncell
30 μm15 μm
![Page 92: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/92.jpg)
• Concept 35.2: Meristems generate cells for new organs
• Apical meristems– Are located at the tips of roots and in the buds
of shoots– Elongate shoots and roots through primary
growth
![Page 93: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/93.jpg)
• Lateral meristems– Add thickness to woody plants through
secondary growth
![Page 94: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/94.jpg)
• An overview of primary and secondary growth
Figure. 35.10
In woody plants, there are lateral meristems that add secondary
growth, increasing the girth of
roots and stems.
Apical meristemsadd primary growth,or growth in length.
Vascularcambium
Corkcambium
Lateralmeristems
Root apicalmeristems
Primary growth in stems
Epidermis
CortexPrimary phloem
Primary xylem
Pith
Secondary growth in stems
PeridermCorkcambium
CortexPrimary phloem
Secondaryphloem
Vascular cambium
Secondaryxylem
Primaryxylem
Pith
Shoot apicalmeristems(in buds)
The corkcambium addssecondarydermal tissue.
The vascularcambium addssecondaryxylem andphloem.
![Page 95: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/95.jpg)
• In woody plants– Primary and secondary growth occur
simultaneously but in different locations
Figure 35.11
This year’s growth(one year old)
Last year’s growth(two years old)
Growth of twoyears ago (threeyears old)
One-year-old sidebranch formedfrom axillary budnear shoot apex
Scars left by terminalbud scales of previouswinters
Leaf scar
Leaf scar
Stem
Leaf scar
Bud scale
Axillary buds
Internode
Node
Terminal bud
![Page 96: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/96.jpg)
• Concept 35.3: Primary growth lengthens roots and shoots
• Primary growth produces the primary plant body, the parts of the root and shoot systems produced by apical meristems
![Page 97: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/97.jpg)
Primary Growth of Roots
• The root tip is covered by a root cap, which protects the delicate apical meristem as the root pushes through soil during primary growth
Figure 35.12
DermalGroundVascular
Key
Cortex Vascular cylinder
Epidermis
Root hairZone ofmaturation
Zone ofelongation
Zone of celldivision
Apicalmeristem
Root cap
100 μm
![Page 98: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/98.jpg)
• The primary growth of roots– Produces the epidermis, ground tissue, and
vascular tissue
![Page 99: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/99.jpg)
• Organization of primary tissues in young roots
Figure 35.13a, b
Cortex
Vascularcylinder
Endodermis
Pericycle
Core ofparenchymacells
Xylem
50 μm
Endodermis
Pericycle
Xylem
Phloem
Key
100 μm
VascularGroundDermal
Phloem
Transverse section of a root with parenchymain the center. The stele of many monocot roots is a vascular cylinder with a core of parenchymasurrounded by a ring of alternating xylem and phloem.
(b)Transverse section of a typical root. In theroots of typical gymnosperms and eudicots, aswell as some monocots, the stele is a vascularcylinder consisting of a lobed core of xylemwith phloem between the lobes.
(a)100 μm
Epidermis
![Page 100: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/100.jpg)
• Lateral roots– Arise from within the pericycle, the outermost
cell layer in the vascular cylinder
Figure 35.14
Cortex
Vascularcylinder
Epidermis
Lateral root
100 μm
1 2
3 4
Emerginglateralroot
![Page 101: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/101.jpg)
Tissue Organization of Stems
• In gymnosperms and most eudicots– The vascular tissue consists of vascular
bundles arranged in a ring
Figure 35.16a
XylemPhloem
Sclerenchyma(fiber cells)
Ground tissueconnecting pith to cortex
Pith
EpidermisVascularbundle
Cortex
Key
Dermal
Ground
Vascular1 mm
(a) A eudicot stem. A eudicot stem (sunflower), withvascular bundles forming a ring. Ground tissue towardthe inside is called pith, and ground tissue toward theoutside is called cortex. (LM of transverse section)
![Page 102: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/102.jpg)
Groundtissue
Epidermis
Vascularbundles
1 mm
(b) A monocot stem. A monocot stem (maize) with vascularbundles scattered throughout the ground tissue. In such anarrangement, ground tissue is not partitioned into pith andcortex. (LM of transverse section)
Figure 35.16b
• In most monocot stems– The vascular bundles are scattered
throughout the ground tissue, rather than forming a ring
![Page 103: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/103.jpg)
Tissue Organization of Leaves• The epidermal barrier in leaves
– Is interrupted by stomata, which allow CO2exchange between the surrounding air and the photosynthetic cells within a leaf
• The ground tissue in a leaf– Is sandwiched between the upper and lower
epidermis• The vascular tissue of each leaf
– Is continuous with the vascular tissue of the stem
![Page 104: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/104.jpg)
Keyto labels
DermalGroundVascular
Guardcells
Stomatal pore
Epidermalcell
50 µmSurface view of a spiderwort(Tradescantia) leaf (LM)
(b)Cuticle
Sclerenchymafibers
Stoma
Upperepidermis
Palisademesophyll
Spongymesophyll
Lowerepidermis
CuticleVein
Guard cells
XylemPhloem
Guard cells
Bundle-sheathcell
Cutaway drawing of leaf tissues(a)
Vein Air spaces Guard cells
100 µmTransverse section of a lilac(Syringa) leaf (LM)
(c)Figure 35.17a–c
• Leaf anatomy
![Page 105: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/105.jpg)
• Concept 35.4: Secondary growth adds girth to stems and roots in woody plants
• Secondary growth– Occurs in stems and roots of woody plants but
rarely in leaves• The secondary plant body
– Consists of the tissues produced by the vascular cambium and cork cambium
![Page 106: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/106.jpg)
The Vascular Cambium and Secondary Vascular Tissue
• The vascular cambium– Is a cylinder of meristematic cells one cell
thick– Develops from parenchyma cells
![Page 107: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/107.jpg)
Vascular cambium
Pith
Primary xylem
Secondary xylem
Vascular cambium
Secondary phloem
Primary phloem
Periderm(mainly cork cambiaand cork)
Pith
Primary xylem
Vascular cambium
Primary phloem
Cortex
Epidermis
Vascular cambium
4 First cork cambium
Secondary xylem (twoyears ofproduction)
PithPrimary xylemVascular cambium
Primary phloem
2
1
6
Growth
Primary xylem
Secondary xylem
Secondary phloem
Primary phloem Cork
Phloem ray3Xylem ray
Growth
Bark
8 Layers of periderm
7 Cork5 Most recentcork cambium
CortexEpidermis
9
In the youngest part of the stem, you can see the primary plant body, as formed by the apical meristem during primary growth. The vascular cambium is beginning to develop.
As primary growth continues to elongate the stem, the portion of the stem formed earlier the same year has already started its secondary growth. This portion increases in girth as fusiforminitials of the vascular cambium form secondary xylem to theinside and secondary phloem to the outside.
The ray initials of the vascular cambium give rise to the xylem and phloem rays.
As the diameter of the vascular cambium increases, thesecondary phloem and other tissues external to the cambium
cannot keep pace with the expansion because the cells no longer divide. As a result, these tissues, including the epidermis, rupture. A second lateral meristem, the cork cambium, develops from parenchyma cells in the cortex. The cork cambium produces cork cells, which replace the epidermis.
In year 2 of secondary growth, the vascular cambium adds to the secondary xylem and phloem, and the cork cambium produces cork.
As the diameter of the stem continues to increase, the outermost tissues exterior to the cork cambium rupture and slough off from the stem.
Cork cambium re-forms in progressively deeper layers of thecortex. When none of the original cortex is left, the cork cambium develops from parenchyma cells in the secondary phloem.
Each cork cambium and the tissues it produces form a layer of periderm.
Bark consists of all tissues exterior to the vascular cambium.
1
2
3
4
5
6
7
8
9
Secondary phloem
(a) Primary and secondary growthin a two-year-old stem
• Primary and secondary growth of a stem
Figure 35.18a
![Page 108: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/108.jpg)
Secondary phloemVascular cambiumLate wood
Early woodSecondaryxylem
CorkcambiumCork
Periderm
(b) Transverse sectionof a three-year-old stem (LM)
Xylem rayBark
0.5 mm0.5 mmFigure 35.18b
![Page 109: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/109.jpg)
• Viewed in transverse section, the vascular cambium– Appears as a ring, with interspersed regions
of dividing cells called fusiform initials and ray initials
Figure 35.19a, b
Vascularcambium
C X CP
CXC
XCPP
PCXX PCXX
C C
Types of cell division. An initial can divide transversely to form two cambial initials (C) or radially to form an initial and either a xylem (X) or phloem (P) cell.
(a)
Accumulation of secondary growth. Although shown here as alternately adding xylem and phloem, a cambial initial usuallyproduces much more xylem.
(b)
![Page 110: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/110.jpg)
• As a tree or woody shrub ages– The older layers of secondary xylem, the
heartwood, no longer transport water and minerals
• The outer layers, known as sapwood– Still transport materials through the xylem
![Page 111: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/111.jpg)
Growth ring
Vascularray
Heartwood
Sapwood
Vascular cambium
Secondary phloem
Layers of periderm
Secondaryxylem
Bark
Figure 35.20
![Page 112: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/112.jpg)
Cork Cambia and the Production of Periderm
• The cork cambium– Gives rise to the secondary plant body’s
protective covering, or periderm
![Page 113: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/113.jpg)
• Periderm– Consists of the cork cambium plus the layers of
cork cells it produces• Bark
– Consists of all the tissues external to the vascular cambium, including secondary phloem and periderm
![Page 114: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/114.jpg)
• Concept 35.5: Growth, morphogenesis, and differentiation produce the plant body
• The three developmental processes of growth, morphogenesis, and cellular differentiation– Act in concert to transform the fertilized egg into
a plant
![Page 115: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/115.jpg)
Molecular Biology: Revolutionizing the Study of
Plants• New techniques and model systems
– Are catalyzing explosive progress in our understanding of plants
![Page 116: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/116.jpg)
• Arabidopsis– Is the first plant to have its entire genome
sequencedCell organization and biogenesis (1.7%)
DNA metabolism (1.8%)Carbohydrate metabolism (2.4%)
Signal transduction (2.6%)Protein biosynthesis (2.7%)
Electron transport(3%)
Proteinmodification (3.7%)
Proteinmetabolism (5.7%)Transcription (6.1%)
Other metabolism (6.6%)
Transport (8.5%)
Other biologicalprocesses (18.6%)
Unknown(36.6%)
Figure 35.21
![Page 117: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/117.jpg)
Growth: Cell Division and Cell Expansion
• By increasing cell number– Cell division in meristems increases the
potential for growth• Cell expansion
– Accounts for the actual increase in plant size
![Page 118: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/118.jpg)
The Plane and Symmetry of Cell Division
• The plane (direction) and symmetry of cell division– Are immensely important in determining plant
form
![Page 119: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/119.jpg)
• If the planes of division of cells are parallel to the plane of the first division– A single file of cells will be produced
Figure 35.22a
Division insame plane
Plane ofcell division
Single file of cells forms
Cube forms
Nucleus
Cell divisions in the same plane produce a single file of cells, whereas cell divisions in three planes give rise to a cube.(a)
Division inthree planes
![Page 120: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/120.jpg)
• If the planes of division vary randomly– Asymmetrical cell division occurs
Figure 35.22b
Unspecializedepidermal cell
cell division
Asymmetrical
Unspecializedepidermal cell
Guard cell“mother cell”
Unspecializedepidermal cell
Developingguard cells
(b) An asymmetrical cell division precedes the development of epidermal guard cells, the cells that borderstomata (see Figure 35.17).
![Page 121: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/121.jpg)
• The plane in which a cell divides– Is determined during late interphase
• Microtubules in the cytoplasm– Become concentrated into a ring called the
preprophase band
![Page 122: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/122.jpg)
Preprophase bandsof microtubules
Nuclei
Cell plates
10 µm
Figure 35.23
![Page 123: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/123.jpg)
Orientation of Cell Expansion
• Plant cells– Rarely expand equally in all directions
![Page 124: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/124.jpg)
• The orientation of the cytoskeleton– Affects the direction of cell elongation by
controlling the orientation of cellulose microfibrils within the cell wall
Figure 35.24
Cellulosemicrofibrils
Vacuoles
Nucleus
5 µm
![Page 125: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/125.jpg)
Microtubules and Plant Growth
• Studies of fass mutants of Arabidopsis– Have confirmed the importance of
cytoplasmic microtubules in cell division and expansion
Figure 35.25a–c Wild-type seedling
fass seedling
Mature fass mutant(a)
(b)
(c)
![Page 126: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/126.jpg)
Morphogenesis and Pattern Formation
• Pattern formation– Is the development of specific structures in
specific locations– Is determined by positional information in the
form of signals that indicate to each cell its location
![Page 127: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/127.jpg)
• Polarity– Is one type of positional information
• In the gnom mutant of Arabidopsis– The establishment of polarity is defective
Figure 35.26
![Page 128: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/128.jpg)
• Morphogenesis in plants, as in other multicellular organisms– Is often under the control of homeotic genes
Figure 35.27
![Page 129: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/129.jpg)
Gene Expression and Control of Cellular Differentiation
• In cellular differentiation– Cells of a developing organism synthesize
different proteins and diverge in structure and function even though they have a common genome
![Page 130: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/130.jpg)
• Cellular differentiation– To a large extent depends on positional
information– Is affected by homeotic genes
Figure 35.28
When epidermal cells border a single corticalcell, the homeotic gene GLABRA-2 is selectivelyexpressed, and these cells will remain hairless.(The blue color in this light micrograph indi-cates cells in which GLABRA-2 is expressed.)
Here an epidermal cell borders twocortical cells. GLABRA-2 is not expressed,and the cell will develop a root hair.
The ring of cells external to the epi-dermal layer is composed of rootcap cells that will be sloughed off asthe root hairs start to differentiate.
Corticalcells
20 µm
![Page 131: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/131.jpg)
Location and a Cell’s Developmental Fate
• A cell’s position in a developing organ– Determines its pathway of differentiation
![Page 132: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/132.jpg)
Shifts in Development: Phase Changes
• Plants pass through developmental phases, called phase changes– Developing from a juvenile phase to an adult
vegetative phase to an adult reproductive phase
![Page 133: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/133.jpg)
• The most obvious morphological changes– Typically occur in leaf size and shape
Leaves produced by adult phaseof apical meristem
Leaves produced by juvenile phaseof apical meristem
Figure 35.29
![Page 134: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/134.jpg)
Genetic Control of Flowering
• Flower formation– Involves a phase change from vegetative
growth to reproductive growth– Is triggered by a combination of
environmental cues and internal signals
![Page 135: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/135.jpg)
• The transition from vegetative growth to flowering– Is associated with the switching-on of floral
meristem identity genes
![Page 136: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/136.jpg)
• Plant biologists have identified several organ identity genes– That regulate the development of floral
pattern
Figure 35.30a, b
(a) Normal Arabidopsis flower. Arabidopsisnormally has four whorls of flower parts: sepals(Se), petals (Pe), stamens (St), and carpels (Ca).
(b) Abnormal Arabidopsis flower. Reseachers haveidentified several mutations of organ identity genes that cause abnormal flowers to develop.This flower has an extra set of petals in place of stamens and an internal flower where normal plants have carpels.
Ca
St
Pe
Se
Pe
Pe
Se
Pe
Se
![Page 137: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/137.jpg)
• The ABC model of flower formation– Identifies how floral organ identity genes
direct the formation of the four types of floral organs
PetalsStamens
CarpelsAB
Sepals
C
C geneactivityB + C
geneactivity
A + Bgene
activity
A geneactivity
(a) A schematic diagram of the ABChypothesis. Studies of plant mutationsreveal that three classes of organ identitygenes are responsible for the spatial patternof floral parts. These genes are designated A,B, and C in this schematic diagram of a floralmeristem in transverse view. These genesregulate expression of other genesresponsible for development of sepals,petals, stamens, and carpels. Sepals developfrom the meristematic region where only Agenes are active. Petals develop where bothA and B genes are expressed. Stamens arisewhere B and C genes are active. Carpels arisewhere only C genes are expressed.
Figure 35.31a
![Page 138: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/138.jpg)
• An understanding of mutants of the organ identity genes
– Depicts how this model accounts for floral phenotypes
Figure 35.31b
StamenCarpel
Petal
SepalWild type Mutant lacking A Mutant lacking B Mutant lacking C
Activegenes:Whorls:
A A C CC C AA CCCCCCCC A A CC C C AB B B B B B B B
A A B B A A B B AA A A A
(b) Side view of organ identity mutant flowers. Combining the modelshown in part (a) with the rule that if A gene or C gene activity is
missing, the other activity spreads through all four whorls, we can explain thephenotypes of mutants lacking a functional A, B, or C organ identity gene.
![Page 139: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/139.jpg)
![Page 140: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/140.jpg)
Se deposita por fuera de la cofia
Es secretada por las células del ápice de la raíz.
Está formada por polisacáridos, principalmente el ác. poligalacturónico.
Capa de mucílago = Mucigel
Funciones posibles:
1)Evitar la deshidratación del ápice de la raíz.
2) Proteger del estrés mecánico que representa penetrar en un suelo compacto, lubrificando el paso de
la raíz a través de del interior del suelo.
3) Proteger de la punta de la raíz contra metales tóxicos ya que el poligalacturano tiene carga negativa
y puede captar los cationes tóxicos.
4) 5) Los ácidos grasos y esteroles en el mucigel pueden ayudar al establecimiento de simbiosis
benéficiosas con microorganismos del suelo.
![Page 141: Exomorfolog A](https://reader034.fdocumento.com/reader034/viewer/2022042613/5528abb149795917048b4b0b/html5/thumbnails/141.jpg)
Figure 35.4a–epneumatóforos