UNIT 9 - Plant Biology Flashcards
List the main parts of the plant distingusihing the shoot system from the root system.
SHOOT SYSTEM
- reproductive shoot (flower)
- apical bud
- node
- internode
- vegetative shoot
- axillary bud
- stem
LEAF
- blade
- petiole
ROOT
- taproot
- lateral (branch) roots
State the function of the stem
supports leaves in the sunlight and transports organic materials, ions and water between roots and leaves
State the location and function of the terminal and axillary bud
terminal bud - top of the stem
axillary bud - axil of each leaf
new cells are produced at these growing points
State the general function of the leaf
photosynthesis
State the general function of the root
anchors the plant and is the site of absorption of water and ions from the soil
List the four main functions of stems
- support for and the elevation of leaves, flowers and fruits - keep the leaves in light
- transport of fluids between the roots and shoots in the xylem and phloem
- storage of nutrients
- production of new living tissue - through meristems
List the tissues present in the stem
- epidermis
- cortex (chlorenchyma)
- fibre cap (sclerenchyma)
- phloem
- xylem
- pith (parenchyma)
Define epidermis
outer layer of wax-coated cells that provides protection and covering
Define cortex
primary tissues of a stem externally bound by the epidermis and internally by the phloem
Define xylem vessels
dead cells with no cytoplasm with varying degrees of lignin thickening in their walls with end walls dissolved leaving a continuous tube
Define and state the function of lignin
tough impermeable material that can be laid down in the primary cellulose wall to strengthen the cell and provide support
What two components is xylem composed of and what is their function
- tracheid’s (all vascular plants) - tapered cells that exchange water solely via pits leading to a slower rate of water transfer
- vessel elements (in only certain vascular plants) - the end walls have becomes fused to form a continuous tube, resulting in a faster rate of water transfer
State the two ways of lignin deposition in xylem vessels
- circular rings in annular vessels - equal distance from each other
- helix/coil in spiral vessels
XYLEM COMPONENTS
- vessel element
- tracheid
LIGNIN ARRANGEMENTS
- annular
- spiral
State how does water and minerals from the soil enter the xylem
through the epidermis of roots, cross the root cortex and pass into the vascular cylinder -> it’s called xylem sap.
Define the phloem tissue
living tissue consisting of sieve tubes and companion cells, responsible for active translocation of sucrose and amino acids from the source (photosynthetic tissues and storage organs) to sink (fruits, seeds and roots)
State what does phloem tissue consist of
it’s a living tissue consisting of sieve tubes and companion cells.
Describe the structure of sieve tubes
narrow, elongated elements
end walls (sieve plates) perforated by pores
cytoplasm has no nucleus
State the function of phloem tissue
active translocation of sucrose and amino acids from source (photosynthetic tissues and storage organs to sink (fruits, seeds, roots)
State the adaptation of the sieve-tube elements
reduction in cell contents enabling the nutrients to pass more easily through it
like the pored sieve plates
State the function of companion cells and define them in phloem
nonconducting cell which is connected to the sieve tube by numerous plasmodesmata
help load sugars into the sieve tube elements
and its nucleus and ribosomes serve for the adjacent sieve tube element
Describe the external structure of a leaf
- leaf blade
- petiole - leaf stalk
- stipules - leaf-like appendages at the base of the leaf
Describe the internal structure of a leaf
- epidermis - outer layer of tissues
- cuticle - waxy protective outer layer of epidermis
- leaf hairs - part of the epidermis
- stomata - natural opening in leaves and herbaceous stems that allow for gas exchange
- guard cells - specialized kidney-shaped cells that open and close the stomata
- palisade layer - tightly packed layer of parenchyma tissues filled with chloroplasts for photosynthesis
- chloroplasts
- vascular bundle - xylem and phloem tissues
- spongy mesophyll - layer of parenchyma tissues loosely arranged to facilitate movement of gases
State the function of the root system
mineral ion and water uptake
State the adaptation for its function of the root system
huge surface area increased by branching of roots and root hairs
Define root hairs
extensions of individual epidermal cells
Describe the tissue distribution in the root and how it relates to the uptake of materials absorbed
materials absorbed diffuse across the cortex and towards the central stele (where xylem is)
the stele is surrounded by a layer of endodermis impermeable to the passive flow of water and ions (Casparian strip) and so they need to be pumped across this barrier by specialized cells allowing for the control of the process.
List the three main ways in which water and minerals are absorbed from root hairs to the xylem.
- mass flow through the interconnecting free spaces between the cellulose fibres of the plant cell walls
- diffusion through the cytoplasm of cells
- osmosis from vacuole to vacuole of the cells
State and explain the alternative name for the mass flow way of water transport from root hairs to the xylem
apoplast
as it entirely avoids the living content of cells while also including the water-filled spaces of dead cells.
State and explain the alternative name for the diffusion through the cytoplasm of cells way of water transport from root hairs to the xylem.
Symplast.
Explanation here
Define a Casparian strip and its function
a belt made of suberin (waxy material)
because it’s impermeable to water and dissolved materials they must cross the selectively permeable membrane of an endodermal cell before they enter the vascular cylinder and thus keeps many unneeded or toxic substances out and prevents leakages back into soil solution.
Distinguish between the symplast an apoplast in short
apoplast - the continuum of cell walls and extracellular spaces
symplast - the continuum of cytosol connected by plasmodesmata