Studies on the growth and fruiting in the tomato, I.

Abstract

1. Effect of thermoperiods on the vegetative and reproductive response.Tomato seedlings were grown and tested under each of six thermoperiods: all combinations of day temperatures (24°C and 30°C) with night temperatures (17°, 24° and 30°C).High day temperature induces the vigorous growth followed by the acceleration of the flower differentiation and its development, whereas higher night temperature restricts the plant growth, being followed by the retardation of the flower bud differentiation, the increase in the number of leaves to the first inflorescence and the decreased number of flowers with the retardation of their developmental growth.It may be concluded that the most favorable thermoperiod for the plant growth, flower formation and fruit production is day temperature 24°C: night temperature 17°C2. Effect of low night temperature at various stages of plant growth on flowering behavior.Tomato seedlings were subjected to the low night temperature of 17°C at various stages of plant growth, and after the treatment the night temperature was raised to 26°C. During the course of this experiment the day temperature was maintained at 24°C.It was found that exposure of seedlings to low night temperature for at least 2 weeks just after cotyledon expansion resulted in the least number of leaves to the first inflorescence.The flower numbers in the first, the second and the third inflorescence reach the maximum respectively by three, five and seven week-exposure to low night temperature from the cotyledon expansion.These results show that the flower formation of the respective inflorescence needs a long temperature treatment previous to the morphological flower bud formation. This is determined by the observation, under the microscope.3. The stem width and the temperature as related to the flower differentiation.In general, the first inflorescence differentiates at the time when the stem diameter just below the cotyledon reaches 2.4-2.8mm, but it does not always follow that the seedlings grown under any environmental conditions form flower buds when they reach this critical size. Lower night temperature stimulates the earlier flower formation, the vegetative growth being somewhat suppressed. The flower bud differentiation is not necessarily associated with the sum of the daily mean temperature from the cotyledon expansion.4. Relationships detween the flower formation and chemical constituents in tomato seedlings.The results of the chemical analysis in the top of seedlings grown under the various combinations of day and night temperature for 50 days from the cotyledon expansion show that the higher the content of carbohydrates, especially total sugars and nitrogen compounds especially protein, the greater the increase in the total number of flowers up to the third inflorescence. The flower bud differentiation and the flower bud development are favored by a high level of carbohydrates and nitrogen compounds.It is concluded that the seedlings, having been grown under the favorable thermoperiods, are heavy in weight in contrast to the plant height, high in total sugar and protein contents, bloom earlier and produce a high yield.