Explain how abiotic factors affect plants (20 mks)

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Wind;

  • 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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