Plant biology - leaves

what part of the leaf finishes first?

the tip, base finishes the last. overall growth is determinate.

how do leaves cool?

thru transpiration, release of water thru the leaves

define reproductive leaves

tiny plantlets produced from leaves, occur in some air plants (epiphytes)

what does xylem transport

water absorbed by the roots

what occurs in the stomata?

water loss and CO2 intake

how do leaves get rid of waste?

when leaves are shed - leaves accumulate metabolic waste products in their leaves

what remains after leaf abcission?

xylem vessels, which are weak and lose the leaf to wind and rain

Veins (AKA, composed of, etc)

AKA bundle sheath, surrounds xylema nd phloem tissues

name the 3 leaf attachment types

alternate, opposite, whorled

what is trade off?

balancing act in which when water is limited, the plant must strike a balance between transpiration and photosynthesis

define sheath

basal appendage, encloses stem

define stipulte

basal appendages

define a compound blade

blade divided into seperate segments/leaflets

what does phloem transport

carbs produced in the mesophyll

define window leaves

carpetweed fam, exposed ends of leaves covered with ttransparent thick epidermis with a waxy cuticle. light penetrates iwndows to chloroplasts in mesophyll

what are bundle sheath extensions?

cells extending from bundle sheath to uppr and ;ower epidermis, allow for support and conduction. either parenchyma cells or fibers.

define decidious

decidous trees have leaves that normally live thru one growing season

why do leafs change color in the fall?

in fall, chlorophyll breaks down, and the other colors from other pigments begin to show

define leaf

lateral outgrowth from the stem, usually consisting of a stalk (petiole) and a flattened blade

define hypodermis

layer of thick lwalled cells beneath the epidermis that minimize winter water loss (found in pine needles)

define phyllotaxy

leaf attachment types

define a pinnately compound leaf

leaflets arranged along central axis (rachis)

define a palmately compound leaf

leaflets arranged from one central point

define evergreen

leaves of evergreen trees life up to 7 years

what are environmental cues that cause leafs to fall off?

lowering temps, decreasing day lengths, lack of water, damage to leaf

describe the mesophyll of the leaf

made up of chlorenchyma cells. main region responsible for photosynthesis.

define floral leaves (bracts)

modified leaf - found at base of flowers or flower stalks, function to attract pollinators

define flower pot leaves

modified leaf - leaves develop into urnlike ouches, ants bring in soil, plant forms adventitous roots and new plants can develop

define tendrils

modified leaf that aids in climbing

insect trapping leaves

modified leaf to trap insects

define storage leaves

modified leaf, includes succulent leaves of many desert plants, no chloroplasts - used for water storage

what is the marginal meristem?

occurs along the margins of the leaf primorium, band of cells. responsible for the blade.

define reituclately veined

occurs in dicots, is netted

define dichotomous veined

occurs in ginkgo, forked

define parallel veined

occurs in monocots

define pinnately veined

one primary vein (called the midvein), secondary veins branch from midvein

2 layers of dicot mesophyll

pallisade mesophyll - uppermost spongy mesophyll - loosely arranged, lower region

describe leaf abcission

seperation of leaf from stem, results from formation of abcission zone. structureal and chemical changes in petiole or leaf base.

define palmately veined

several primary veins fan out from base of the blade

describe the epidermis of a leaf

single layer of cells covering the entire surface of a leaf. do not have chloroplasts, except for guard cells. produces way cuticke. glands and crystals of waste may occur in the epidermis.

define petiole

stalk (when there is no petiole is sessie)

define cladophyll

stem that resembles a leaf, takes over photosynthetic function (EX asparagus, cactui)

describe guard cells

surround stomata. contain chloroplasts - inflate or delfate with amount of water within, when inflated, stomata are open, when deflated, stomata are closed.

how do plants in arid regions minimize water loss?

having thick, leathery leaves and fewer or sunken stomata

name the 2 strucutal changes that occur to cause leaf abcission

1. seperation layer - short cells with thin cell walls making leaf base weak. enzymes break down cell walls in seperation layer, hydrolysis of cellulose walls. 2. protective layer: suberized cells that form below abcission layer, forms leaf scar

define a simple blade

a blade undivided into segments

define petiolate

a leaf that is attached by a stalk or stem

define sessile

a leaf that is attached directly by the base, no petiole

define blade

expanded, main photosynthetic portion

where do leaves originate from?

founder cells in the peripheral part of the apical meristem, which develop into leaf primordia, hwich eventually become mature leaves

what is found in the mesophyll?

ground tissue - parenchyma cells with chloroplasts, and intercellular spaces

what is broken down by enzymes to destruct the middle lamella?

pectin

primary leaf function

photosynthetic organ of the plant

name the 5 leaf venation patterns

pinnately veined, palmately veined, paralell, reticulate, and dichotomous

define stomata

pores surrounded by two guard cells, which allows gas exchange. usually on lower epidermis.