Explain how abiotic factors affect plants (20 mks)
Wind;
Temperature;
Light
Humidity;
pH
Salinity;
Topography;
Rainfall / Water;
Pressure;
Mineral salts;
- In windy conditions the rate of transpiration increases; wind dispenses fruits / seed / spores;
- Wind is an agent of pollination;
Temperature;
- Changes in temperature affect the rate of photosynthesis / other biochemical reactions;
- Increase in temperature increases the rate of transpiration;
Light
- Plants need light for photosynthesis;
- Some plants need light for flowering;
- Some seeds (lettuce) require light for germination;
Humidity;
- When humidity is low the rate of transpiration increases; accept converse
pH
- Each plant requires a specific PH to grow well;
- Affect biochemical reactions
Salinity;
- Plants with salt tolerant tissues; grow in saline areas
- Plants in estuaries adjust to salt fluctuations;
Topography;
- North facing slopes in temperate land have more plants than south facing slopes;
- Plants on lee ward side have stunted plants; (And wind ward has normal growth for plants)
Rainfall / Water;
- Fewer plants in deserts where rainfall is less;
- Water is required for seed germination;
- Is a raw material for photosynthesis;
- Dissolves mineral salts / solvent;
- Provides rigidity for support;
- Medium for transport;
- Dispersal of fruit / seeds / spores;
Pressure;
- Variation in atmospheric pressure affects availability of CO2 ; which affects photosynthesis; and low pressure increase rate of transpiration; and affect amount of O2; for respiration;
Mineral salts;
- Affect distribution of plants in the soil;
- Plants thrive best volume the elements are present;
- Plants living in soil deficient in a particular element must have special methods of obtaining it;
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