Growth and Development of Buckwheat under Differential Temperature Gradients

Abstract

1. The ontogenetic cycle of common buckwheat, Fagopyrum esculentum, grown under greenhouse conditions in gravel cultures maintained at uniform levels of water and nutrient supply, was traced from germination to maturity. Growth and developmental responses of plants whose roots and shoots were maintained at differential temperatures were compared with controls in which entire plants were grown under uniformly high or low temperature conditions. 2. Major growth and developmental responses noted were: a) The apparent major factor in determining the duration of the developmental cycle in buckwheat is the temperature of the air (shoot temperature). b) High air temperatures curtailed the vegetative phase and shortened the lifespan. Anthesis occurred earlier, and maturity and senescence were rapid at higher air temperature. Leaves were numerous, but the water requirement per unit of dry weight was low. High air temperature increased accumulation of inorganic material (ash). c) Low air temperature, on the other hand, prolonged ontogeny considerably. Thus, in the series with low shoot and high root temperature, no seeds had formed when the experiment was terminated, and the plants were still growing actively. Increase in duration of the vegetative phase did not, however, result in any commensurate increase in amount of plant material produced. The percentage of ash of entire plants was less at low than at high air temperatures. d) Water consumption followed a similar curve for all series, being the lowest at the time of floral primordia inception followed by a secondary increase concurrent with seed formation. The total amount of water absorbed was increased by high soil temperatures. e) Changes in pH value of leachates reflected differences in rate and amount of the metabolic activity of the different series and were closely correlated with the resultant structural alterations. Rapid vegetative growth was associated with a decrease in pH value of leachates followed by a slow increase coincident with flower inception. A secondary increase in hydrion concentration accompanied anthesis and syngamy, but with the onset of maturity and senescence pH values shifted upward again. f) A balanced temperature condition (shoots and roots at the same temperature) was more conducive to normal development of buckwheat than differential root and shoot temperatures. In terms of dry-weight yield, the treatment with the higher soil and air temperature (H/H) was most beneficial. g) If a distinction is made between growth and development on the basis, respectively, of increase in size as opposed to rapidity of progression through the life-cycle, the shoot temperature appears primarily to regulate development and root temperature to influence chiefly the general growth processes in this particular annual.