Factors which Influence Growth of Plants:
- Types of factors.
- Genetic Factors.
- Environmental factors.
- Moisture supply.
- Radiant energy.
- Atmospheric composition.
- Toxic atmospheric substances.
- Soil structure and soil aeration.
- Soil PH.
- Biotic factors.
- Supply of minerals.
- Growth restricting substances.
Two types of factor influence plant growth; genetic and environmental.
Plant growth is proportional to its genetic constitution. A plant cannot exceed its genetic capacity even in the presence of best possible inputs.
Optimum temperature for growth varies with specie, stage, region of plant.
Standard: (15-40)C. Variation in requirement of Temperature.
Duration of exposure to light.
Stage and age of plant.
- Enzyme activity.
- Absorption of nutrients, H20
- Cell-well permeability.
- Temperature and Photosynthesis = (if Co2 is limitig)
- Temperature and Respiration = Vice versa.
- Temperature and Transpiration & vice versa.
- Temperature and absorption of nutrients.
- Temperature and enzyme Micro-organism Pop and activity.
ii. Moisture Supply:
Growth of plant is proportional to optimum and timely water supply.
Extremes (low and high) hinders plant growth. How?
- Reduction in cell division and cell elongation.
- Reduction in microorganism activity.
- Reduction in root development and
- Reduction in uptake of nutrients etc.
Plants use water to
- Manufacture carbohydrates.
- Maintain hydration of protoplasm.
- Translocation of food and mineral elements. Different plants have different moisture sensitive stages (moisture level critically important).
Citrus => fruit setting, flowering.
Cotton => flowering and boll development.
Wheat => crown root initiation and heading.
iii. Radiant Energy:
Behaviour of plant in relation to daylight is called photoperiodism. Plants differ in their response to day light. Day light of 3/4 days bring Good results.
iv. Atmospheric composition:
Response of plant to levels of carbon dioxide in the atmosphere: C-3 plants have more positive response towards carbon dioxide than C-4 plants.
v. Toxic Atmospheric Substances:
When in excess, Co, So2, HF, … Toxic to plants (Aid Rain)
How aid rain affects the plant growth?
- Leading out of organic and inorganic minerals from soil.
- Leaf erosion and damage.
- Alteration of response to pathogens.
- Low seed germination.
- Decrease in respiration etc.
- Low establishment of conifers.
- Reduced availability of soil nitrogen.
vi. Soil Structure and soil aeration:
Good soil structure → good soil aeration and water availability.
High bulk density of soil → More soil → Inhibit the emergence of seedlings and offer mechanical resistance to root penetration.
Low pore compaction spaces → Poor aeration of O2 and low water availability.
vii. Soil PH:
Influences availability of nutrients to plants. PH > 7, Nitrogen in soil becomes ammonia and volatizes.
Conversion of phosphorous fertilizer to insoluble derivatives.#
viii. Biotic Factors:
Heavier, unnecessary and untimely ferlization results in.
- Greater weed growth which competes with plant/crop for water, nutrients and light.
- Insect infestation (cotton weevil).
- Viruses and nematodes attack which attack the root, hinders mineral absorption capability of roots, requiring double fertilization but no good to plant.#
ix. Supply of Minerals:
Adequate supply of micro-nutrients such as Zn, Ca, Mg, S, B, Fe, Mo, Mn etc. Adequate supply of macro-nutrients such as N,P and K.
Some are present in soil naturally. Others have to be provided timely.
x. Growth restricting substances:
When in excess, even beneficial substances such as N,P,K etc are toxic to plants. Toxic substances even in small account. Al, Ni, Ar, Mo, Cl2, Co, Cd, Hg, Pb, Li, St, Be, V, I2, Sb etc.
Sources of toxic substances in soil.
- Metallurgical industry/work.
- Animal and poultry enterprises.
- Pulp and paper mills.
- Food processing industries etc.