Chapter 7: Leaves

concepts

bud, spines

provide protection

tendrils

support

fleshy leaves of bulbs

storage

Parts-of-a-Leaf-Diagram External structure of foliage leaves

most obvious function is photosynthesis

leaf blade:

flat light harvesting portion also called lamina

dorsal surface

blade's lower surface

ventral surface

upper side; usually smooth

petiole

hold the blade out into the light

sessile leaf

type of leaf blade

when leaves are small or very long and marrow, there may be no petiole

simple leaf

compound leaf

has a blade of just one part

has a blade divided into several individual parts

Vein

bundle of vascular tissue within a leaf

reticulate venation

the netted pattern in basal angiosperm and eudicots

parallel venation

the veins runs side by side with few obvious interconnections in monocots with long , strap-shaped leaves

abscission zone

cells of it involved incutting off the leaf when its useful life is over

Internal structure of foliage leaves internal st

mesophyll

vascular tissue

Epidermis

petiole

Flat, thin foliage leave, optimal for light interception

have a large surface through water can be lost

transpiration

water loss through the epidermis

can be serious problem is soil is dry, root cannot replace water

waterproof and translucent

allows entry of carbondioxide

ground tissue interior to the leaf epidermis

Palisade parenchyma

layer of cells along the upper surface of most leaves

main photosynthetic tissue of most plant

spongy mesophyll

lower portion of leaf permits carbondioxide to diffuse rapidly away from stomata into all parts of leaf's interior

A eudicot leaf usually has one large midrib

lateral veins emerge from midrib and then branches into narrow minor vein

Bundle sheath: many fibers arrange as bundle in leaf

minor veins are important for releasing water from xylem and loading sugar into phloem

midrib and lateral rib involve in conduction

Bundle sheath extension: help give rigidity to the blade and provide an additional water to moves from bundle out to the mesophyll

part of leaf and are transition between the stem and the lamina

contain fewer stoma and trichome

leaf traces: branches from stem vascular bundles and diverge towards the petiole

stipules: in many species, the pwtiole bears two small flaps of tissue at its base called stipules.

Initiation of development of leaves Schematic-views-of-leaf-development-A-The-overview-of-dicot-leaf-development-Leaf

basal angiosperm and eudicots

Monocots

leaf primordium

At the base of meristem, cells just interior to the protoderm grow outward called leaf primordium

Grows so rapidly that it becomes taller than the shoot apical meristem

As leaf primordium grows upward, it increases the thickness, establishing the bulk of midribs

initiated by the expansion of some shoot apical meristem cells to form a leaf primodium

Apical meristem become the part of perimodium give hoodlike shape

Morphology and anatomy of other leaf types

spines

bud scale buds01

tendrils

leaves with kranz anatomy

leaves of conifer

Sclerophyllous foliage leaves

insect trape insect traps

Succulent leaves how-to-propagate-succulents-from-leaves-and-cuttings-needlesandleaves_net

Permits plant to survive in desert

Thick and fleshy

reduce the surface to volume ratio and favors water conservation

mesophyll are transparent and contain very few air spaces

Produce more sugar by photosynthesis

Soft, flexible and edible

less amount of sclerenchyma

leaves are sclerophylls

thick cutivle and their epidermis and hypodermis have thick walls

most of them contain unpalatable chemicals

always simple never compound, have only a few form

provide protection

small, rarely compound

petiole is either short or absent

tougher and waxier

modified leaves of axillary buds

no blade and are needle shaped

no mesophyll parenchyma or vascular tissue is present

Another form of modified leaf

grows indefinitely

Contain cells that are capable of sensing contact with an object

response by sensing solid objects and growing around them.

have special metabolism called c4 metabolism

lack palisade parenchyma and spongy mesophyll

Have prominent bundle of sheaths composed of large chlorophyllous cell

Ability of leaves to trape and digest insect

grows in habitat poor in nitates and ammonia.

by digesting insects, plant obtain nitrogen they need for amino acid and nucleotides

two types

active trap

passive trap

moves during capture

incapable of movement

eg: leaves of sundew

upper surface of foliage is covered with glandular trichomesthat secrete a sticky digestive liquid

trichome and lamina are able to sense the present of insects

has numerous stomata and vascular bundles as well as mesophyll

eg: pitcher leaves of Nepenthes

thin, parenchymatous and capable of photosynthesis

lamina is tubular and secrets a watery digestive fluid