lab 4 terms Flashcards
phyllotaxy
the arrangement of leaves on a stem
alternate phyllotaxy
leaf arrangement where there is one leaf per node; there are two types of alternate phyllotaxy: alternate distichous and alternate spiral
alternate distichous phyllotaxy
leaf arrangement where there is one leaf per node and leaves are arranged in two rows, 180 degrees from each other; leaves are in a single plane
alternate spiral phyllotaxy
leaf arrangement where there is one leaf per node and leaves are arranged in a spiral around the stem
opposite phyllotaxy
leaf arrangement where there are two leaves per node and leaves are arranged in pairs across the stem from each other; there are two types of opposite phyllotaxy: opposite distichous and opposite decussate
opposite distichous phyllotaxy
leaf arrangement where there are two leaves per node and leaves are arranged in pairs across the stem from each other; pairs of leaves are in a single plane
opposite decussate phyllotaxy
leaf arrangement where there are two leaves per node and leaves are arranged in pairs across the stem from each other; successive pairs of leaves are at right angles to one another
whorled phyllotaxy
leaf arrangement where there are three or more leaves per node
venation
the pattern of veins within a leaf
pinnate reticulate venation
the pattern of veins within a leaf where there is a midrib and veins branch from it with larger veins branching into smaller veins
reticulate (netted) venation
the pattern of veins within a leaf where the veins form a network, branching from larger to smaller veins; characteristic of eudicots
palmate reticulate venation
the pattern of veins within a leaf where there are several large veins (no midrib) branching from the top of the petiole that branch into smaller and smaller veins
adaxial surface
the upper surface of the leaf
abaxial surface
the lower surface of the leaf
leaf sheath
part of a leaf in some monocots (grasses); the base of the leaf that wraps around the stem
parallel venation
the pattern of veins within a leaf where there is usually a midrib with several other large veins running parallel to it for the length of the leaf blade; there are typically many tiny cross veins that join the parallel veins along their length; characteristic of monocots
ligule
a small outgrowth of a monocot (grass) leaf at the point where the leaf blade meets the leaf sheath
simple leaf
a leaf where the blade is not divided into distinct parts
compound leaf
a leaf where the blade is divided into leaflets, usually each with its own small stalk
pinnately compound leaf
a compound leaf where the leaflets arise from other side of an axis, the rachis (resembles a feather)
palmately compound leaf
a compound leaf where the leaflets all arise from the top of the petiole (there is no rachis)
leaflet
one of the part of the blade of a compound leaf
rachis
the central axis of a pinnately compound lead to which the leaflets attach
stipule
an outgrowth from the base of the petiole of a leaf; often in pairs
sessile leaf
a leaf which lacks a petiole; the blade attaches directly to the node
photosynthesis
the conversion of light energy to chemical energy; the production of carbohydrates from CO2 and water in the presence of light and chlorophyll, using light energy
tendril
a modified leaf or leaflet (or stem); modified into a slender, coiling structure which grows around other plants or objects to help support the plant
spine
a modified leaf; modified into a hard, sharp-pointed structure; often for protection from herbivores
prickle
a sharp, pointed outgrowth of the epidermis of a leaf or stem (a rose’s ‘thorns’ are actually prickles); for protection from herbivores
bulb
a specialized underground bud with thick, fleshy leaves (both the leaves and the stem are modified); the bulb functions in vegetative reproduction - the leaves of the bulb function in food storage
bud scale
small, hard leaves which surround and protect shoot buds (often over the winter)
carnivorous plant
plants with leaves modified in a variety of ways to entrap insects to enhance nutrition (venus flytrap, sundew, pitcher plant, etc)
chloroplast
a organelle (a plastid) within a plant cell which contains pigments such as chlorophyll a and is responsible for photosynthesis
endodermis
a single layer of cells forming a sheath around the vascular region in roots and some stems and leaves (pine)
mesophyll
the ground tissue (parenchyma) of a leaf lying between the upper and lower epidermis and interspersed with veins; consists of cells with many chloroplasts and often with large intercellular spaces - for photosynthesis
palisade mesophyll
a layer of mesophyll in the top half of the leaf with long rectangular cells oriented to take full advantage of sunlight
spongy mesophyll
a layer of mesophyll in the bottom half of the leaf with loosely-arranged cells surrounded by large intercellular spaces
chlorophyll a
the main photosynthetic pigment which traps light energy; absorbs light with wavelengths that peak at 430nm (violet and blue) and at 662nm (orange and red)
chlorophyll b
an accessory photosynthetic pigment; absorbs light with wavelengths that peak at 453nm (blue and green) and at 660nm (orange)
carotenoid pigments
a group of accessory photosynthetic pigments, including carotenes and xanthophylls
xanthohyll
an accessory photosynthetic pigment; one of the carotenoid pigments which absorbs light with wavelengths that peak at 450nm (blue and green)
carotene
an accessory photosynthetic pigment; one of the carotenoid pigments which absorbs light with wavelengths that peak at 440nm (violet) and 470nm (blue)
