Practical significance of low night temperature in the tomato nursery. III.

Abstract

Effects of high and low night temperatures and varying amounts of fertilizer (small, medium and large) in the nursery on the growth of tomato plants were examined, based on the following idea:Reproductive growth is closely related to vegetative growth in tomato plants. In consideration of this relation, the author proposed the following formula for reproductive growth:R/T=(R/V)•(V/T)where R, V and T represent the amount of reproductive growth, the amount of vegetative growth, and time, respectively. With this formula reproductive growth (R/T) may be analyzed in terms of two components: (1) the relative growth of the reproductive and vegetative parts (R/V); and (2) the vegetative growth (V/T). The bud diameter of the first flower on each inflorescence was used as a measure of reproductive growth and the total dry weight of a plant as a measure of vegetative growth.When the log of the bud diameter was plotted against the log of the total dry weight of a plant, a linear relation was observed and the points were fitted by a regression line. On the basis of this relation it was possible to analyze the effects of the nursery conditions on the first component of reproductive growth from the shifting of the slope and the level of the regression line.A low night temperature exerted a differential effect on each component of reproductive growth. The first flower bud on every inflorescence was initiated at an earlier stage of vegetative growth with low night temperatures and this resulted in an increase of R/V. On the other hand, the rate of vegetative growth preceding the unfolding of foliage leaves decreased with low night temperatures.A large amount of fertilizer led to a reduction in the both components. The initiation of the flower bud on the lower inflorescence occurred at a later stage of vegetative growth when a large amount of fertilizer was used. The vegetative growth preceding the unfolding of foliage leaves also declined when a large amount of fertilizer was used.An interaction between temperature and amount of fertilizer was observed. The effect of low night temperatures was largest when a medium amount of fertilizer was used and was decreased or nullified by using a large amount.Following flower bud inititaion, the relative growth of the bud on each inflorescence and vegetative part was not largely affected by the external conditions in this experiment. The regression coefficients did not deviate significantly from 0.66. Bud growth was measured in length, and vegetative growth by weight. If the third power of length is proportional to the weight, it is possible to compare the relation between bud and vegetative growth in the same weight unit by trebling the regression coefficient. About 2.0 was obtained by multiplying 0.66 by 3. It was, therefore, presumed that the relative growth rate of the bud was generally twice as high as that of the vegetative part. But an increasing slope of the regression line was observed in successive inflorescences with high night temperatures and bud growth attained to three times as large as the vegetative growth in the third inflorescence.Performance of the tomato plants following transplanting seemed to be largely characterized by nursery conditions and the plants grown at low night temperatures and with a mdium amount of fertilizer yielded the most superior results.