Bot-Lec (Sem-1) - Chapter 14: Leaves

leaves

main site for photosynthesis

simple; compound

two types of leaves

simple leaf

a leaf that is undivided/no leaflets

compound leaf

a leaf that is divided into several leaflets

phyllotaxy

the leaf arrangement on the stem which is determined by the number of leaves per node

alternate; opposite; whorled

three types of phyllotaxy

alternate

phyllotaxy type; one leaf per node

opposite

phyllotaxy type; two leaves per node

whorled

phyllotaxy type; three or more leaves per node

epidermis; guard cells; stomata; spongy mesophyll; palisade mesophyll; vascular bundles

six parts of the internal anatomy of leaves

epidermis

part of the internal anatomy of leaves; innermost layer with trichomes and pores called stomata

stomata

part of the internal anatomy of leaves; areas of gas exchange and lead directly into the spongy mesophyll

guard cells

part of the internal anatomy of leaves; specialized cells flanking the stomata that open or close depending on the prevailing conditions

spongy mesophyll

part of the internal anatomy of leaves; parenchymatous region with air spaces

palisade mesophyll

part of the internal anatomy of leaves; with usually columnar parenchymatous cells with abundant chloroplasts where photosynthesis take place

vascular bundles

part of the internal anatomy of leaves; scattered throughout the mesophyll that bring water to the cells of the leaves and take away the products of photosynthesis to be used in other parts of the plant

lamina; petiole; leaf margin; leaf apex; leaf base; veins

six parts of the external anatomy of leaves

lamina

part of the external anatomy of leaves; the leaf blade

petiole

part of the external anatomy of leaves; the stalk that connects the leaf to the stem

leaf margin

part of the external anatomy of leaves; the lateral borders of the leaf; can be whole or serrated

leaf apex

part of the external anatomy of leaves; the very tip/protruding part of the leaf

leaf base

part of the external anatomy of leaves; the very base of the leaf; slightly expanded area where the leaf attaches to the stem

veins

part of the external anatomy of leaves; branches from the midrib and is present throughout the lamina; can be netted or parallel

xerophytes; hydrophytes; mesophytes

three adaptations in leaf anatomy

xerophytes

plants that are adapted for drier environments; require very little water

hydrophytes

plants that are adapted for aquatic environments; can be emergent, submerged, or floating

mesophytes

plants that are adapted for environments that are neither too hot or too cold; require moderate amount of water

bracts; bud scales; bulb scales; seed leaves; spines; storage leaves; tendrils

seven types of modified and specialized leaves

bracts

leaves that have lost its photosynthetic capability and instead contains other pigments; attractants for prospective pollinators and as protective sheaths

foliaceous; petaloid; spathe

three types of bracts

foliaceous bracts

a type of bract that resembles the leaves of plants

petaloid bracts

a type of bract that resembles flower petals

spathe

a single large bract that subtends an inflorescence; very distinctive in arums such as Anthurium and Spathiphyllum; encloses the spadix entirely or partly

Euphorbia pulcherrima

poinsettia; plants with bracts

Zingiberales

order of families with bracts; includes bananas, gingers, and birds-of-paradise

bud scales

cover the growing tips where new leaves or flowers are being formed; protect these parts and when the leaves/flowers are mature enough, they open and sometimes fall off

bulb scales

the aromatic fleshy parts of onions and garlic bulbs and these are modified for storage of food; adaptive feature for life in temperate regions; during the winter months, the plant lays dormant, surviving only on the stored food

seed leaves/cotyledons

nutritive tissues in embryos for seed plants; derive their nutrients from the endosperm formed during double fertilization

spines

in contrast to thorns, are thin, sharp protections that prevents herbivory; also reflective; minimizing heat stress on the plant

storage leaves

fleshy and thickened to store food and water; e.g. Aloe vera

Aloe barbadensis

aloe vera; an example of storage leaves

tendrils

are the curly/spiral appendages found in the axillary regions that allow certain vines to climb other plants and structures

Vitaceae

grape family; example of tendrils

carnivorous plants

evolved to have leaves that capture and digest small animals; still capable of photosynthesis; they need to catch and digest animals because the areas where they live in are usually acidic bogs that contain little or no nitrogen compounds

cup-like/pitcher-like leaves; flypaper style; active traps

three types of carnivorous plant leaves

cup-like/pitcher-like leaves

contains a liquid mixture of water and digestive enzymes; an insect could slip down on the slick sides of the leaves with downward pointing bristles to prevent it from escaping; the insect drowns and is digested; released nutrients are absorbed by the leaves

Nepenthes

Asian pitcher

Sarracenia

North American pitcher

flypaper style

found in butterwort plants of the genus Pinguicula and in the more famous sundews of the genus Drosera; spread with scattered sticky trichomes; curl to envelop trapped insects, effectively killing and then digesting it; curl their leaves via increased mitosis on only one side of the leaf; opening of the leaf traps is by fast mitosis on the other side

Pinguicula

genus of butterworts; carnivorous flypaper style

Drosera

genus of sundews; carnivorous flypaper style

active traps

modified into clam-shaped structures with fringing spines; each leaf has three trigger hairs; once triggered, the leaf snaps shut, effectively capturing the prey and slowly digesting it; aquatic counterpart known as bladderworts of the genus Utricularia

Utricularia

genus of bladderworts; aquatic carnivorous active plants; air bladders that when triggered opens to let in a torrent of water carrying along the prey