Long-Term Chilling of young Tomato plants under low light and Subsequent Recovery. 1. Growth, development and Photsynthesis.

The influence of unfavourable climatic conditions at the onset of the growth period on chilling-sensitive tomato (Lycopersicon esculentum Mill., cv. Abunda) was studied by exposing young plants to combinations of low temperature and low light (60-100-mu-mol quanta . m-2 . s-1) for several weeks. When the temperature did not decrease below a critical point (8-degrees-C) no loss of developmental capacity of the plants was detected. However, while new leaves were readily formed upon return to normal growth conditions (22/18-degrees-C, day/night, in a greenhouse), net accumulation of biomass showed a lag phase of approximately one week. This delay was accompanied by a strong, irreversible inhibition of photosynthesis in the fully expanded leaves which had been exposed to the chilling treatment. When plants were subjected to temperatures below 8-degrees-C, survival rates decreased after three weeks at 6-degrees-C and irreversible damage of apical meristematic tissue occurred. Drought-hardening prior to chilling ensured survival at 6-degrees-C and protected the plants against meristem loss.