Plant Anatomy And Physiology Flashcards
Osmosis
Movement of water from a high water potential to a low water potential across a semi-permeable membrane. It is a passive process that requires NO energy
Diffusion
Mostly for gasses. Movement of any substance (even water) from a high to a low concentration. Passive process with no energy and no membrane needed.
Active transport
Movement of substances against the concentration gradient.
ares with little of substance to areas with a lot already.
E.g.- movement of glucose from lumen of intestine ( low concentration of glucose ) into the cells of the villi (high concentration of glucose). This requires energy , cell breaks down ATP (adenosine triphosphate) into ADP ( adenosine di phosphate ) to release energy
What is a Tissue system
Group of plant cells working together to perform a certain function =tissues
Tissues = many diff cell types
Plants gave higher level of structure = plant tissue system .
Name the four types of plant tissue systems
Meristematic
Dermal
Group tissue- parenchyma (most abundant) ,collenchyma, sclerenchyma
Vascular tissue - xylem and phloem
Primary structure of root, stem, leaf in dicotyledonous plants
Plant organs are group of tissues work together to perform certain functions, name them. They are present in primary structure in young plants.
Roots- anchor plant , absorb water + mineral salts
Stem - support, transport sub from leaf to root to leaf, orientate plant for optimal photosynthesis
Leaf- photosynthesis, organic nutrient production
Flower- an organ designed to maximize pollination into fertilization
Fruit - a deep dispersal organ
Structure in dicotyledonous roots
Name the layers in primary dicot root with function from outside
1) Epidermis - single layer of thin walled cells, root hairs made from those cells. F- protection , absorption ( water, mineral salts)
2) Cortex- lies beneath epidermis, makes bulk of primary root, consists of parenchyma. F- stores food, conducts water+ mineral salts across root.
3) Endodermis - innermost layer of cortex. Thin layer of tightly packed cells. Endodermis cells have casperian strips ( thick, waterproof, waxy band of Suberin , in radial cell walls. F- regulate flow of water+ m.s between cortex and stele.
4) Vascular cylinder - pericycle (outer part of meristematic tissues gives rise to lateral roots. Stele ( xylem at center for w+ m.s transport), vascular cambium (meristematic + makes xylem and phloem), columns of phloem (transport food from leaves to roots)
Structure of a dicot stem
Name layers in young dicot stem that’s undergoing primary structure growth from outside to inside.
Cuticle- waxy layer secreted with epidermis. F- prevent w loss through evaporation though stem and reflects sun off plant stem keeping cool = reduces w loss
Epidermis- single layer. F- protects stem from mechanical damage, produce trichomes( hair-like out growths , may protect plant from desiccation by reflecting sunlight + reducing w.p.g in air near stem, frighten off herbivores.
Collenchyma - 2-3 layers , below epidermis. F- support in green stems.
Cortex- many layers of parenchyma. F- store food+ w + support.
Endodermis- contains lots of starch, not casperian strips.
Vascular bundle- sclerenchyma cap( pericycle) :protects vascular bundle. Phloem - transport food. V.C - meristematic, rise to xylem and phloem. Xylem- transport w+ m.s
Pith- made of parenchyma. F- support
Passage of water through the plant
Water of water is unidirectional
Name the process for movement from soil to xylem
Soil-> root hair (w enters by osmosis) (cross root hair membrane, high in soil to low in root hair water potential) ( w through cytoplasm of root hair across the tonoplast ( vascular membrane) of root hair into vacuole with low water potential ) -> cortex of root-> endodermis-> pericycle-> xylem
What makes xylem vessels suited to their function of water transport ?
Form continuous tube- walls are highly pitted or absent
Dead or empty so subs can move easily
Cells walls have lignin - strong prevents collapsing under strong suction pressure
Lignin- water proof = can’t escape
Narrow = forces of capillary possible
Pits- water move in and out , function to release air locks
Patterns of lignin - laid down, strength, water proofing without vessels becoming rigid
Water movement up xylem
2 mechanisms - name
Transportation pull
Root pressure
Explain transpirtation pull and root pressure
T.P- water up stem, low water potential in leaves then w moves from xylem to leaf mesophyll = pressure diff at top of xylem vessel. Result water pulled up xylem vessel . Water is known as transpiration stream. Water rises as unbroken steam due to forces of cohesion btw water molecule and adhesion btw w.m and vessel walls( capillarity) - very narrow tubes ( xylem vessels)
R.P- active process inorganic irons pumped into xylem vessels, from surrounding cells. This lowers water potential in xylem , water is drawn down into xylem from other cells- water entering cells increase w.p at base of xylem result water pushed up xylem .
Movement of water across leaf
Transpiration is loss of water vapour from plant. - in stomata of leaves, cuticle of plant , lenticels in woody stems.
W -> across leaves ( bc w evaporates from intercellular air spaces out of open stomata )- causes mesophyll cells to loose water from surfaces into intercellular air spaces, w then replaced from adjacent mesophyll cells- w.p.g developing across leaf to .i.a to xylem( w.p higher). W moves osmotically from xylem cross m.c into .i.a then evaporated. = water lose = transpiration
Plants in dry areas have anatomical features that limit transpiration , what are they ?
Vertical arrangement of leaves ( less surface exposed to sun)
Sunken stomata
Hairs on leaves
Thickened cuticles
Factors that affect transpiration rate
Wind
High temps - evaporation
Low humidity
High light intensity
