Topic 9: Plant Biology

Guard cells

● ________ minimise water loss, which controls the aperture of the stoma.

Fungi

________ facilitate the movement of mineral ions into the root hair cell.

Roots

________ that are growing or absorbing mineral ions using energy from cell respiration.

Hydrogen ions

________ are pumped out of the companion cells into the interstitial spaces of the cell wall of the companion cell.

Germination

________: After absorption of water, metabolic rate of seed increases, and energy is released by aerobic respiration.

companion cell

O Sucrose converted to oligosaccharide in the ________ to maintain the sucrose concentration gradient.

Plant hormones

________ affect shoot growth: Plant hormones control growth in the shoot apex.

Cotyledons

________ are the embryo leaves and contain the food reserves of the seed.

Warmth

________ is required for enzyme functionality during germination.

Plants

Replacing losses from transpiration: ________ transport water from roots to leaves to replace losses from transpiration.

Tension

________ in leaf cell walls maintains the transpiration stream: Adhesive property of water and evaporation generate ________ forces in leaf cell walls.

Micropropagation

________ is used for rapid bulking up: Viruses are transported within a plant from cell- to- cell through vascular tissue and via plasmodesmata.

cytokinins

O Ratio between ________ and auxin determine whether development in the axillary bud will occur.

Cells

________ in the meristem are small but increase in volume by absorbing nutrients and water.

Intracellular pumps

________: Auxin efflux pumps set up concentration gradients of auxin in plant tissue.

Vegetative structures

________: roots, stems and leaves.

● Energy

________ is required to generate pressures (active process)

● Embryo root shoot

________ require sugars for growth and glucose for aerobic respiration.

Cacti

________: Leaves are reduced in size.

Mineral ions

________ are absorbed into the thread- like hyphae of the fungi and are supplied to the plant.

Temperature

________ plays a role in transforming leaf- producing shoot into flower- producing shoot.

Carbon dioxide

________ is absorbed at night and stored as malic acid, which then released carbon dioxide slowly during the day to be used for photosynthesis whilst stoma are kept closed.

Sucrose

________ is withdrawn from phloem at the sink end of the phloem and used as an energy source or converted to starch.

Gravitropism

________: Gravity causes cellular organelles caused statoliths to accumulate at the tip of roots.

Auxins

________ have a broad range of functions: initiating growth of roots, development of fruits and regulating leaf development.

Xylem structure

________ helps withstand low pressure: Cohesive property of water and the structure of xylem vessels allow transport under tension.

Micropyle

________ is a small hole through the testa.

● Loss

________ of solute results in reduction in osmotic pressure and water is drawn back into the transpiration stream (xylem)

Xylem structure helps withstand low pressure

● Cohesive property of water and the structure of xylem vessels allow transport under tension

● Xylem

long continuous tubes, walls thickened with lignin, which strengthens the wall to withstand very low internal pressures

● Cohesion

o Formed due to hydrogen bonding in water, due to its polar structure

● Adhesion

o Water is attracted to hydrophilic parts of the xylem

Tension in leaf cell walls maintains the transpiration stream

● Adhesive property of water and evaporation generate tension forces in leaf cell walls

Active transport of minerals in the roots

● Active uptake of mineral ions in the roots causes absorption of water by osmosis

● Water movement from roots into xylem o Apoplast pathway

through the cell walls

o Symplast pathway

through the cytoplasm

Replacing losses from transpiration

● Plants transport water from roots to leaves to replace losses from transpiration

o Ephemeral

short life cycle, only alive during rainfall

o Perennial

Store water in specialised leaves, stems/ roots

o Cacti

Leaves are reduced in size

● Halophytes (saline soil plants)

o Has salt concentration higher than in the saline soils surrounding it

Photosynthetic tissues

● Mature green leaves

Parts of the plant that are growing or develop food stores

● Fruits

Storage organs that are unloading their stores

● Storage tissues in germinating seeds

● Tap roots or tubers at the start of growth season Phloem loading

● Active transport is used to load organic compounds into phloem sieve tubes at the source

● Apoplast route

o Sucrose travels from cell walls of mesophyll cells to cell walls of companion cells

● Symplast route

o Sucrose travels through plasmodesmata, which run between cells

Pressure and water potential differences play a role in translocation

● Incompressibility of water allows transport by hydrostatic pressure gradients

Phloem sieve tubes

● Sieve tubes consist of sieve tube cells

9.3 Growth in plants Growth in plants

● Undifferentiated cells in the meristems of plants allow indeterminate growth

● Apical meristem can give rise to specialised cells

procambium (vascular tissue), protoderm (epidermis) and ground tissue (pith)

Plant hormones affect shoot growth

● Plant hormones control growth in the shoot apex

● Auxins have a broad range of functions

initiating growth of roots, development of fruits and regulating leaf development

Plant tropisms

● Plants respond to the environment by tropisms

Auxin influences gene expression

● Auxin influences cell growth rates by changing the pattern of gene expression

Intracellular pumps

● Auxin efflux pumps set up concentration gradients of auxin in plant tissue

● Gravitropism

o Gravity causes cellular organelles caused statoliths to accumulate at the tip of roots

Micropropagation of plants

● In vitro procedure that produces large numbers of identical plants

● If growth media contains a 10

1 ratio of auxins to cytokinins then roots develop (rooting media)

If less than 10

1 then shoots develop (shoot media)

Micropropagation is used for rapid bulking up

● Viruses are transported within a plant from cell-to-cell through vascular tissue and via plasmodesmata

● Vegetative structures

roots, stems and leaves

● Long day

o Activation of pigment phytochrome results in transcription of FT gene (flowering time)

o This transforms leaf-producing apical meristems into reproductive meristems Photoperiods and flowers

● Switch to flowering is a response to the length of light and dark periods in many plants

Inducing plants to flower out of season

● Plants can be induced to flower out of season

● Pollinators gain food from nectar and plants gain a means to reproduce

hence mutualism

● Germination

o After absorption of water, metabolic rate of seed increases, and energy is released by aerobic respiration