Explain how a biotic factors affect plants

K.C.S.E Biology Q & A - MODEL 2004PP1QN19

Explain how a biotic factors affect plants

answers

Wind.
In windy conditions the rate of transpiration increases; wind disperses fruits/ seeds; is an agent of pollination; acc. Spores for seed.
Temperature
Changes in temperatures affects the rate of photosynthesis  and other biochemical reactions/ metabolic reactions/ enzymatic reactions/ enzymatic reactions, temperature increases rate of transpiration;
Lights
Plants need light for  photosynthesis, some plants need light for flowering/ photoperiodism/ seeds like lettuce require  light for germination.
Humidity
When humidity is low, the rate  of transpiration increases;
PH
Each  plant  requires a specific pH to grow well/ acidic/ alkalinity/ neutral;
Salinity
Plants with salt tolerant tissues grow in saline area, plants in estuaries adjust to salt fluctuations;
Topography
North facing slopes in temperature  lands have more plants than south facing slope
Plants on windward side have  stunted/ distorted growth;
 Comparisons of mountains and valleys
 Description  of other areas with other topographies e.g. River valley rainfall/ water
- Fewer plants  in areas/ semi arid  and
- Water is needed for germination/ is a raw material for  photosynthesis/ dissolves/ minerals salts/ provides turgidity for support/ fruits/ seeds
Pressure;
Variation in atmospheric pressure affect availability of CO+2+ which affects  photosynthesis and low  pressure increase rate  of transpiration; and affect  amount  of oxygen; for respiration
Mineral salts/ trace  elements
- Affects distribution of plants  in the soils
- Plants thrive well where there are mineral salts in the soil
Plants living  in the soil deficient  in particular mineral element have special methods obtaining it; for example  legumes obtaining  from nitrogen by fixation or carnivorous.