Reduction of respiration in fine roots of tea [plant] induced by hard pruning: Correlation to root rot disorder

The first stage of the symptons of root rot disorder are considered to be browning and rotting of fine roots. To clarify the factors which contribute this first stage of disorder, we examined the effect of pruning on the respiration of fine roots mainly using two varieties, 'Yabukita' and 'Fu-jimidori' which are sensitive and resistant to the disorder, respectively. The respiration of fine roots decreased proportional to the magnitude of pruning. The decrease was smaller in 'Okumusashi', 'Fujimidori' and 'Sayamakaori' than that in'Yabukita', 'Kurasawa', 'Okumidori' and 'Kanayamidori'. This varietal difference was corresponded with the sensitivity to the disorder. Treatment of excess-fertilization also induced the decrease of the fine root respiration. This decrease was slightly larger in 'Fujimidori' than in 'Yabukita'. By flooding condition of two days, also, the fine root respiration decreased. The magnitude of decrease and the restoration after the treatment were the same between 'Yabukita' and 'Fujimidori'. When tea plants were treated with excessfertilization or flooding condition of two days in addition to pruning, the decrease of fine root respiration was large compared to pruning alone. These results indicate that hard pruning induces the first stage of the symptons of disorder, and both excess-fertilization and flooding condition accelerate the disorder induced by pruning.