Light is the primary energy source for all plant life, as photosynthesis is entirely light-driven.

Quantity (Intensity): Up to a threshold, greater intensity increases food production. Low light suppresses photosynthesis, resulting in etiolation (thin, spindly stems).

Quality (Wavelength): Blue light (~400–500 nm) drives vegetative growth, while red light (~600–700 nm) combined with blue encourages flowering.

Duration (Photoperiod): The length of uninterrupted darkness regulates flowering (e.g., Short-day vs. Long-day plants).

Influences photosynthesis, respiration, transpiration, germination, and flowering.

Thermoperiod: Plants grow best when daytime temperatures are 10–15°C higher than nighttime temperatures.

Germination: Cool-season crops need 15–18°C; warm-season crops need 18–24°C.

Effects: Cool nights can make winter squash sweeter, while high temperatures can cause bitter lettuce. Peaches require 700–1,000 hours of 0–7°C dormancy.

Water constitutes approximately 90% of a plant's living tissue.

Critical Roles: Turgor pressure (maintains cell shape), nutrient solvent, transpiration cooling, and stomatal regulation.

Humidity: Affects the rate of transpiration.

• >80%: Impairs transpiration and promotes fungal infections.
• <30%: Causes rapid moisture loss and leaf scorch.
• 50–70%: Optimal for balanced transpiration.

Plants require 17 essential chemical elements. Carbon, Hydrogen, and Oxygen come from air/water; 14 must come from the soil.

Soil pH: A master variable controlling nutrient availability. Optimal range is pH 6.0–7.0.

Gases: Higher atmospheric CO₂ increases photosynthetic rates. Oxygen is required for aerobic root respiration; overwatering flushes O₂, causing root rot.

Important Note: Fertilisers are not plant food; they merely supply mineral raw materials.

High year-round rainfall and temperatures (25–35°C) support continuous rapid growth — trees do not shed leaves seasonally.

Features: Extremely high biodiversity, dense multi-layered canopy, buttress roots, and epiphytes.

Species: Mahogany, Rosewood, Ebony, Bamboo.

Most widespread vegetation type in India. Trees shed leaves during distinct dry periods to reduce water loss.

Features: Trees shed leaves during Oct–Nov and grow new ones in Mar–Apr. Richer in organic matter than rainforests.

Species: Teak, Sal, Sandalwood, Bamboo.

Extreme aridity and high evapotranspiration force plants to adopt drought-resistant (xerophytic) adaptations.

Features: Long tap roots, thick fleshy stems to store water, and thorny leaves to reduce transpiration.

Species: Acacia, Babul, Cactus, Khejri.

Pronounced cold winter makes photosynthesis impossible, so trees shed leaves in autumn to conserve energy.

Features: Dramatic seasonal colour change; rich brown forest soils due to annual leaf litter.

Species: Oak, Beech, Maple, Elm.

Cold temperatures and short growing seasons (3–4 months) demand highly specialised adaptations.

Features: Conical tree shapes allow heavy snow to slide off. Needle-shaped leaves have a thick waxy cuticle. Acidic podzol soils.

Species: Pine, Spruce, Fir, Cedar.

Tropical (Savanna): 75–150 cm rain with a 4–6 month dry season. Periodic fires maintain grass dominance. Deep root systems survive drought.

Temperate: 25–75 cm rain. Low irregular rainfall prevents tree establishment. Deep, rich chernozem (black earth) soils form.

Found along tropical coastlines, tolerating saline water, tidal flooding, and anaerobic muddy soils.

Features: Survive through salt exclusion, salt secretion, and pneumatophores (aerial breathing roots). Distinctive prop and stilt roots.

Species: Sundari, Rhizophora.

Temperatures remain below freezing most of the year. Permafrost prevents deep root penetration.

Features: No trees due to cold and wind. Low-growing plants with cushion-form habits and dark pigmentation.

Species: Mosses, lichens, sedges, dwarf willows.

Light is the primary energy source for all plant life, as photosynthesis is entirely light-driven.

Quantity (Intensity): Up to a threshold, greater intensity increases food production. Low light suppresses photosynthesis, resulting in etiolation (thin, spindly stems).

Quality (Wavelength): Blue light (~400–500 nm) drives vegetative growth, while red light (~600–700 nm) combined with blue encourages flowering.

Duration (Photoperiod): The length of uninterrupted darkness regulates flowering (e.g., Short-day vs. Long-day plants).

Influences photosynthesis, respiration, transpiration, germination, and flowering.

Thermoperiod: Plants grow best when daytime temperatures are 10–15°C higher than nighttime temperatures.

Germination: Cool-season crops need 15–18°C; warm-season crops need 18–24°C.

Effects: Cool nights can make winter squash sweeter, while high temperatures can cause bitter lettuce. Peaches require 700–1,000 hours of 0–7°C dormancy.

Water constitutes approximately 90% of a plant's living tissue.

Critical Roles: Turgor pressure (maintains cell shape), nutrient solvent, transpiration cooling, and stomatal regulation.

Humidity: Affects the rate of transpiration.

• >80%: Impairs transpiration and promotes fungal infections.
• <30%: Causes rapid moisture loss and leaf scorch.
• 50–70%: Optimal for balanced transpiration.

Plants require 17 essential chemical elements. Carbon, Hydrogen, and Oxygen come from air/water; 14 must come from the soil.

Soil pH: A master variable controlling nutrient availability. Optimal range is pH 6.0–7.0.

Gases: Higher atmospheric CO₂ increases photosynthetic rates. Oxygen is required for aerobic root respiration; overwatering flushes O₂, causing root rot.

Important Note: Fertilisers are not plant food; they merely supply mineral raw materials.

High year-round rainfall and temperatures (25–35°C) support continuous rapid growth — trees do not shed leaves seasonally.

Features: Extremely high biodiversity, dense multi-layered canopy, buttress roots, and epiphytes.

Species: Mahogany, Rosewood, Ebony, Bamboo.

Most widespread vegetation type in India. Trees shed leaves during distinct dry periods to reduce water loss.

Features: Trees shed leaves during Oct–Nov and grow new ones in Mar–Apr. Richer in organic matter than rainforests.

Species: Teak, Sal, Sandalwood, Bamboo.

Extreme aridity and high evapotranspiration force plants to adopt drought-resistant (xerophytic) adaptations.

Features: Long tap roots, thick fleshy stems to store water, and thorny leaves to reduce transpiration.

Species: Acacia, Babul, Cactus, Khejri.

Pronounced cold winter makes photosynthesis impossible, so trees shed leaves in autumn to conserve energy.

Features: Dramatic seasonal colour change; rich brown forest soils due to annual leaf litter.

Species: Oak, Beech, Maple, Elm.

Cold temperatures and short growing seasons (3–4 months) demand highly specialised adaptations.

Features: Conical tree shapes allow heavy snow to slide off. Needle-shaped leaves have a thick waxy cuticle. Acidic podzol soils.

Species: Pine, Spruce, Fir, Cedar.

Tropical (Savanna): 75–150 cm rain with a 4–6 month dry season. Periodic fires maintain grass dominance. Deep root systems survive drought.

Temperate: 25–75 cm rain. Low irregular rainfall prevents tree establishment. Deep, rich chernozem (black earth) soils form.

Found along tropical coastlines, tolerating saline water, tidal flooding, and anaerobic muddy soils.

Features: Survive through salt exclusion, salt secretion, and pneumatophores (aerial breathing roots). Distinctive prop and stilt roots.

Species: Sundari, Rhizophora.

Temperatures remain below freezing most of the year. Permafrost prevents deep root penetration.

Features: No trees due to cold and wind. Low-growing plants with cushion-form habits and dark pigmentation.

Species: Mosses, lichens, sedges, dwarf willows.