Effect of Temperature on Seed Germination and Flowering of Horticultural Plants
Temperature is one of the most critical environmental factors influencing various physiological processes in horticultural plants, including seed germination and flowering. Both these stages are highly sensitive to temperature variations, and understanding their relationship helps in improving crop management and productivity.
1. Effect of Temperature on Seed Germination
Seed germination is the process by which a seed develops into a seedling. It involves the activation of enzymes, water absorption, and growth of the embryonic root (radicle) and shoot.
a) Optimum Temperature for Germination
Each horticultural species has a specific temperature range that is most favorable for seed germination, called the optimum temperature. Within this range:
- Enzymatic activities and metabolic processes operate efficiently.
- Water uptake by seeds is optimal.
- Germination rate is highest and uniform.
For example:
- Tomato seeds germinate best between 20°C to 30°C.
- Onion seeds prefer cooler temperatures around 15°C to 20°C.
b) Low Temperature Effect
- At temperatures below the optimum, metabolic processes slow down.
- Seeds may remain dormant or take a longer time to germinate.
- Extremely low temperatures can cause imbibitional injury (damage due to water uptake in cold conditions), leading to seed death.
c) High Temperature Effect
- Temperatures above the optimum can denature enzymes necessary for germination.
- High temperatures cause faster water loss and seed desiccation.
- Some seeds may experience thermo-dormancy, where high heat inhibits germination.
2. Effect of Temperature on Flowering
Flowering is a complex developmental phase controlled by internal genetic factors and external environmental cues, including temperature.
a) Temperature and Flower Initiation
- Temperature affects the initiation and development of floral buds.
- Many horticultural plants require a specific temperature range to switch from vegetative growth to reproductive growth.
- For example, chill-requiring plants like apples and cherries need low winter temperatures (vernalization) to flower properly.
b) Heat and Flowering
- Excessively high temperatures can cause flower bud abortion or prevent flower formation altogether.
- Heat stress may reduce pollen viability and stigma receptivity, leading to poor fruit set in crops like tomato and capsicum.
c) Cold and Flowering
- Some plants require low temperatures to induce flowering (vernalization).
- Others are sensitive to frost, which can damage buds and flowers, reducing yield.
Summary Table
| Process | Low Temperature Effect | Optimum Temperature Effect | High Temperature Effect |
|---|---|---|---|
| Seed Germination | Slow or no germination, dormancy | Fast, uniform germination | Enzyme damage, seed death, thermo-dormancy |
| Flowering | Delayed flowering or vernalization | Proper flower initiation and development | Flower bud abortion, poor fruit set, sterility |
Conclusion
Temperature critically influences both seed germination and flowering in horticultural plants. Maintaining the appropriate temperature range during these stages is essential for ensuring high germination rates, healthy flower development, and ultimately better fruit production. In the Indian context, understanding local temperature patterns helps farmers decide the best sowing times and manage crops effectively to avoid losses due to temperature extremes.