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.