environmental effects on plant growth and development

Question 1

absorbed or

intercepted radiation

Answer 1

The key to the amount of plant production, ; the higher the interception of PAR radiation, the greater the yield of the crop,

Question 2

aerenchyma cells

Answer 2

Specialised cells in some plants , e.g. rice, strawberry clover, many wetland plants, that enable the exchange of
oxygen and other gases from shoots to roots, thereby enabling plant survival and growth in waterlogged, low
oxygen environments

Question 3

aerobic conditions

Answer 3

Soil conditions when oxygen is available for root growth and metabolism

Question 4

anaerobic conditions

Answer 4

A lack of oxygen, usually when soils are waterlogged or flooded often leading to reduced root activity, decreased
mineral nutrient availability or even root death.

Question 5

available water

capacity

Answer 5

The difference between field capacity & wilting point deficit. It represents the water available for plant growth
in a soil.

Question 6

C3 plant

Answer 6

Mainly temperate zone species that just follow the Calvin (C3) photosynthesis cycle. RuBisCO enzymes trap
atmospheric CO2 enabling it to be fixed. C3 plants have growth advantages under cooler, lower light
conditions, compared to C4 plants. Examples: most plants (95+%), e.g. ryegrass, white clover, wheat.

Question 7

C4 plant

Answer 7

Tropical-origin species still use the RuBisCO enzyme but also use the PEPC enzyme to trap atmospheric CO2 for
photosynthesis.
PEPC shuttles & concentrates co2 into surrounding bundle sheath cells (where RuBisCO is located). C4 plants
have growth advantages under hotter, high light conditions, compared to C3 plants. C4 examples are maize,
sorghum, kikuyu, paspalum, summer grass & redroot.

Question 8

chloroplasts

Answer 8

Specialised organelles within a plant cell containing chlorophyll in which carbohydrates (sugars) are synthesised.

Question 9

dark phase

Answer 9

The light independent phase of photosynthesis whereby carbon dioxide is converted into
organic compounds, mainly carbohydrates (sugars) by the enzyme RuBisCO.

Question 10

evapotranspiration

Answer 10

The process in which water is transferred from the land to the atmosphere by transpiration from plants

Question 11

leaf area duration

LAD

Answer 11

Leaf area index over time.

Question 12

leaf area index (LAI)

Answer 12

The area of leaf exposed to light, expressed in relation to the ground surface area beneath the plant; the single
most important determinant of radiation interception and therefore yield

Question 13

light phase

Answer 13

The light dependent phase of photosynthesis whereby light energy is captured by structures called
photosystems

Question 14

4. macronutrient

Answer 14

Nitrogen, phosphorous, potassium & sulphur are the major nutrients required for plant
growth

Question 15

photothermal time

Answer 15

A method of accumulating daily temperatures and photoperiod to help predict phenological development (e.g.
time to flowering) in plants.

Question 16

runoff

Answer 16

Rainfall in excess of soil field capacity is lost as runoff

Question 17

. stomata

Answer 17

a pore on the surface of the leaf which allows carbon dioxide (CO2) to enter and water (H2O)
vapour to exit as transpired water

Question 18

transpiration

Answer 18

The process by which moisture is carried through plants from roots to stomata on leaves, where it changes to
vapour and is released to the atmosphere

Question 19

0. wilting point deficit

Answer 19

Represents the amount of water required to prevent plants wilting (when stomata close & therefore no growth
will occur).

Question 20

what is a mitserlich equation

Answer 20

response of plant growth

to mineral nutrient concentration defficient zone, adaqute zone and a toxic zone