Ethylene involvement in stress responses of horticultural crops

by Kim, Hye-Ji.

Nr (never-ripe) tomato and etr1-1 (ethylene-resistant) petunia plants were evaluated to investigate the effect of ethylene on root and shoot development in response to low phosphorus stress. Adventitious root formation in tomato plants was significantly increased by low phosphorus in wild-type, but not in Nr. Ethylene production by adventitious roots was reduced by low phosphorus in both genotypes. The results suggest that enhanced adventitious root formation in phosphorus deficient wild-type tomato was induced by the increase in tissue sensitivity to ethylene, and that ethylene perception plays an important role in carbon allocation to adventitious roots under low phosphorus stress. Shoot growth of both species was decreased by low phosphorus similarly in ethylene sensitive and resistant genotypes. Reduced ethylene sensitivity of Nr tomato did not affect most plant growth responses to low phosphorus, while ethylene insensitivity of etr1-1 petunia significantly reduced shoot weight, root weight, and total biomass at 4 weeks after transplanting, but not at 7 weeks regardless of phosphorus level. In tomato, the effective quantum yield of photosystem II was affected by phosphorus level at 2 15 weeks after transplanting but not by genotype. However, that of etr1-1 petunia grown with low phosphorus was significantly lower than wild-type at 2 and 4 weeks after transplanting, and sequentially recovered to the level of the wild-type, suggesting that etr1-1 petunia under low phosphorus following transplanting may undergo more severe stress compared to Nr tomato due to the stronger constitutive ethylene insensitivity. Our results demonstrate that ethylene mediates adventitious root formation in response to phosphorus stress and plays an important role for quick recovery of plants imposed to multiple environmental stresses, i.e. transplanting and low phosphorus.