Abstract
The influences of air temperature, soil conditions and fertilization on cold resistance or on the bark splitting injury of young tea plants were investigated using artificial bark splitting technique, electric conductivity method and browning test.
1. The bark splitting injury was not affected by the diurnal range but by the minimum air temperature in the time of the occurrence.
2. The soil temperatures did not affect the occurrence rate of the injury but the size of the split caused under the higher soil temperature was larger than that caused under the lower soil temperature and gradually enlarged with the time of the freezing treatment.
3. The occurrence of the injury markedly decreased with the reduction of soil moisture.
4. The hardening of the young tea plants was accelerated by 3 day's exposure to the air temperature of 0°C.
The increase of the cold resistance by the low air temperature above mentioned was observed 1 week later slightly, and remarkably observed 2-3 weeks later.
The young tea plants exposed to such low air temperature in middle time of the hardening obtained approximately equal cold resistance regardless of the amount of nitrogen applied in autumn.
5. The tea plants in hardening was not dehardened even by the air temperature of 25°C for 1 week.
6. The hardening was gradual untill midOctober or early November but became rapid from about mid-November.
This process almost coincided with the increasing process of the resistance to the bark splitting injury.
