Hardening of the plants in the nursery

• The term hardening includes "Any treatment that makes the tissues firm to withstand unfavourable environment like low temperature, high temperature and hot dry wind."

• Hardening is physiological process .Plants accumulate more carbohydrates reserves and produce additional quiticle on the leaves.
• In this process seedlings are given some artificial shocks at least 7-10 days before uprooting and transplanting. These shocks includes
• o Exposure to the full sunlight,
• o Removal of all the shedding nets, polythene sheets
• o Irrigation is stopped slowly and slowly.

Techniques of hardening

The hardening is done by the following ways.

• By holding the watering to the plant by 4-5 days before transplanting
• Lowering the temperature also retards the growth and adds to the hardening processes.
• By application of 4000 ppm NaCl with irrigation water or by spraying of 2000 ppm of cycocel(Chadhdha,2006).

Duration and degrees of hardening

• It is very necessary that plants should be hardened according to their kind so that there is an assurance of high percentage of survival and slow growth under the condition to be expected at the time of transplanting.
• Hardening should be gradual to prevent or check the growth.
• Warm season crops like tomato, brinjal and chillies do not favour severe hardening. In Indian condition allowing the soil to become dry for 5-6 days does the hardening.

Effect of hardening

The following effect may be observed by the hardening

• Hardening improves the quality and modifies the nature of colloids in the plant cell enabling them to resist the loss of water.
• Hardening increases the presence of dry matter and regards in the plants but decrease the percentage of freezable water and transpiration per unit area of leaf.
• Decreases the rate of growth in the plants
• Hardened plants can withstand better against unfavourable weather conditions like hot day winds or low temperature
• Hardening of the plants increases the waxy covering on the leaves of cabbage.