plant structure

contains info on the roots/shoots system, the plant stems (cork cells), wood/bark morphology, flower anatomy (specifically reproductive anatomy), the composition of a leaf

tap roots

• few structures, but grow long and deep into the ground/long shaft (can access nutrients and water quite well)

• very good at breaking up hardpan substrate 

• not found in shallow soils 

fibrous roots

• more separated structure 

• shorter in length 

• effective in shallow soils 

ex) onions and corn

tuber

swelling within a root structure that can break down carbohydrates for photosynthesis (i.e., sweet potatoes)

prop roots

• emerge from stem just above the ground to support plants in shallower soils (i.e. mangroves in the tropics)

snorkel roots (pneumatophores)

• emerge below ground but rise above ground to obtain CO2 for respiration within the root

• present in species that have roots in water saturated soil or standing water (i.e. mangroves again)

general functions of roots 

• provides moisture and inorganic nutrients (K, N, P) 

• attaches plant to the ground to enable them to reach for radiant energy above ground 

• long term starch storage (i.e. carrots, sweet potatoes) 

• access oxygen (i.e., pneumatophores on mangroves) 

stems, trunks, and shoots

• above the ground, contains nodes and leaves

axial shoots

central columns with spire shape for strength and shedding snows (i.e. pines)

dendritic shoots 

sub-branching which allows for greater photoreception (i.e., dendritic trees)

buttress “roots” (really shoots)

allows for bigger trees and plants to have more support especially in thin tropical soils 

functions of shoots/stems/trunks

• transport nutrients/water between leaves and roots

• access to available light

• asexual reproduction

  • lateral stem runners above ground (stolons) and below (rhizomes)

• photosynthesis (in arid climates, i.e., cactus)

• water storage (i.e., cactus)

• protection (thorns are modified stems)

• food storage (i.e., underground stems like in the white potato or yams)

simple leaf

single blade structure attached to a twig

compound leaf

leaf made up of several leaflets

doubly (compound) leaf

leaflets on leaflets (effective in areas with lots of rainfall so that water droplets don’t end up weighing down the leaves). increases lateral leaf reach with minimal increase in leaf mass

needles (leaf)

gives maximum water conservation; reduced but year round photosynthesis

functions of leaves

• photosynthesis

• water collectors

• attachment (to other vegetation for climbing)

• defense (i.e., most cactus spines are modified leaves)

• water storage (i.e., aloe vera, succulent plants)

• obtaining supplementary nitrogen (i.e., carnivorous plants)

lignin

• located in the secondary cell walls of vascular plants 

• provides structural and mechanical support 

• maximum strength within the xylem tissue 

meristematic cells

• undifferentiated, allows for active growth of plant

• no secondary cell walls, and their primary cell walls are thin to allow for growth and division

parenchyma cells

• most common mature cell in plants

• forms dermal tissue OR can revert back to being meristematic

• makes up phloem cells of the vascular system

• only primary cell walls (thin and flexible)

collenchyme cells

• functions to provide support to the plant (thus they have longer, thicker primary cell walls)

• the strands you see when you break celery sticks are composed of this

sclerenchyma cells

• contains an extra secondary wall “impregnated” with lignin

• only have a function once they die

• the cells that make up the xylem (since it becomes a hollow tube after dying, it allows for the transport of water)

• supportive tissue of elongated fibers (for making rope, hemp, linen)

trichomes 

• located on top of the epidermis (of the leaf)

• grown by the secondary cell wall to prevent herbivory 

epidermis (of the leaf)

• contains the waxy cuticle, trichomes, and stomata 

palisade mesophyll (of the leaf)

• elongated parenchyma cells (hence its name of tall walls)

• primary site of photosynthesis

spongy mesophyll (of the leaf)

• space for gas and H2O exchange

• the cells that make this are also responsible for making phloem

lower epidermis 

• contains thin waxy cuticle 

vascular bundle

• vascular tissue containing xylem, phloem, and supportive collenchyme cells

cork (stem)

• located externally

• the bark of a tree (dark part)

• produced by cork cambium

vascular cambium

creates phloem

heartwood

• the “core” or “pit” aka the dark middle circle, it’s a layer of xylem 

sapwood

• the light colored xylem layer surrounding the dark middle circle

rays

semicircle shapes within the bark that allow for water to move inward to outward

vascular cylinder

• central part of the plant stem

• contains 

  • xylem

  • phloem

  • pericycle (where lateral roots can develop and grow)

  • endodermis (outermost layer of the cortex)

primary growth

• root growth is more involved than shoot

• grows from tip up (outward away from crown)

• site of actively dividing cells

• elongation and absorption zone

• mucigel (lubricant) 

mucigel

acts as a lubricant to reduce friction and allows the roots to penetrate the soil more easily

secondary growth

• caused by lateral meristems (cambium) resulting in increased girth (diameter) of the plant

• direction of growth in a tree is from inside the vascular cambium moving inward

two types of lateral meristems 

1) cork cambium (located outside phloem cells, produces cork (bark) cells

2) vascular cambium (located inside the cork cambium layer) produces phloem cells and doesn’t increase in width much, produces xylem cells and the girth of the tree increases

reproductive anatomy of a flower

• stamen (male): produces the male gametophyte (pollen aka plant sperm)

• carpel (female): produces female gametophytes (and eventually eggs) each composed of a swollen basal ovary, a tubular style, and a terminal stigma (the sticky surface that pollen lands on which allows for fertilization)