Climatic Requirement
Climate
Climate is the principal factor controlling plant growth. It refers to the average condition of the atmosphere over a long period, whereas the term weather describes the current and temporary atmospheric conditions. For successful growth of horticultural plants, components of climate like temperature, humidity, wind, light, rainfall, hail, and frost should be carefully studied.
Although man cannot control these environmental factors, their effects can be altered or managed. For instance:
- Effects of high or low temperature can be adjusted.
- Additional moisture can be provided during dry conditions.
- High wind velocity can be reduced by growing wind breaks around the orchard.
Climate of a region is mainly influenced by:
- a) Latitude
b) Altitude
c) Topography
d) Position relative to continents and oceans
e) Large-scale atmospheric circulation patterns
Important Climatic Components Affecting Horticultural Crops
1. Temperature
Temperature is one of the most vital components of climate. It influences:
- Growth and development
- Respiration, photosynthesis, transpiration
- Uptake of nutrients and water
- Reproduction (pollen viability, fertilization, fruit set)
- Carbohydrate and growth regulator balance
- Maturation, senescence, yield, and shelf life
The plant performs best when temperature remains in its optimum range. Very high or low temperatures disrupt physiological activities.
Classification of Fruit Crops Based on Temperature Requirements:
- Tropical: Mango, Banana, Papaya, Sapota, Pineapple, Coconut, Cashew, Arecanut, Breadfruit, Jackfruit, Avocado
- Subtropical: Guava, Grape, Citrus, Date palm, Phalsa, Pomegranate, Litchi, Loquat
- Temperate: Apple, Pear, Peach, Plum, Quince, Apricot, Walnut, Almond, Strawberry, Cherry
Temperature Ranges:
- Minimum: 4.5°C – 6.5°C (40°F – 43°F)
- Optimum: 24°C – 27°C (75°F – 85°F)
- Maximum: 29.5°C – 45.4°C (85°F – 114°F)
Effects of Low Temperature:
- Desiccation: Imbalance between absorption and transpiration
- Chilling Injury: Disturbance in metabolic and physiological processes
- Freezing Injury: Coagulation due to undercooling of protoplasm
2. Humidity (Moisture) and Frost
- Atmospheric humidity influences the moisture requirement of fruit crops.
- High humidity + High temperature → rapid growth, higher yield, but increased pest and disease incidence.
- Water requirement differs among species:
- Pine tree: 25 liters/kg dry matter
- Apple: 250 liters/kg
- Lucerne: 500 liters/kg
Factors Affecting Water Absorption:
- a) Amount of water in soil
b) Soil texture and structure
c) Root zone or water-absorbing area
Water is lost by transpiration through leaves, which depends on humidity, temperature, wind, and light. Maintaining the balance between uptake and transpiration is vital for plant health.
3. Light
Light is electromagnetic radiation (kinetic energy), reaching the earth as photons or quanta.
Light is essential for photosynthesis, the process by which green cells convert CO₂ and H₂O into carbohydrates using sunlight, releasing O₂.
- a) Light Intensity:
Refers to the number of photons per area. It varies with:
- Day and season
- Latitude and elevation
- Dust, water vapour, and slope
Low Light Symptoms:
- Reduced photosynthesis
- Carbohydrate deficiency → poor growth/yield
- Leaf tip discoloration
- Leaf/bud drop
- Pale leaves/flowers
High Light Symptoms:
- Wilting, graying of leaves due to chlorophyll reduction
- Lowered photosynthesis with continued respiration → low yields
b) Quality of Light: Refers to wavelength. The visible spectrum (photosynthetically active radiation) ranges from 390 – 730 nm.
Photoperiodism:
Response of plants to daily light duration affecting flowering, tuber, and root formation.
Types of Plants Based on Photoperiodism:
- Long Day Plants: Require ≥16 hrs light / ≤8 hrs dark e.g., radish, cauliflower, cabbage, carrot, spinach
- Short Day Plants: Require ≤12 hrs light / ≥10-14 hrs dark e.g., strawberry, potato, sweet potato, chrysanthemum, cosmos, poinsettia
- Day Neutral Plants: Flowering not affected by light duration e.g., tomato, chilli, okra, carnation, dianthus, African violet
- Intermediate Plants: Require specific light duration e.g., wild kidney bean, Indian grass, broom grass
4. Rainfall
- Critical for horticultural crop planning.
- Rain during flowering is detrimental, especially in tropical fruit crops, as many are sensitive to moisture at this stage.
- Rainfall pattern should be studied before orchard establishment.
Wind
- High-speed winds (>100 km/h) can cause total destruction, including tree uprooting.
- Wind can damage flowers and fruits.
- Wind damage can be reduced by planting windbreaks.
Common Windbreak Trees:
- Saru
- Eucalyptus
- Ingadulsis (likely a local/common tree species used for wind protection)
