The Growth Responses of Soybean Plant to Photoperiod and Temperature : III. The effects of photoperiod and temperature on the development and anatomy of photosynthetic organ

Abstract

Developmental and anatomical features of soybean leaves grown under different photoperiod and temperature were compared in consideration for their relations to growth parameters. 1. Leaf number increased with increase of temperature and daylength. The leaflet size of the 5th leaf was greater under long day than under short day, and greatest at 25°C or 30°C day temperature. Thus, relative growth rate of leaf area per plant increased with increase of temperature and under long day condition. The thicknesses of leaf blade, mesophyll and pallisade layer, and specific leaf weight increased with decrease of temperature, whereas leaf area ratio decreased with decrease of temperature. 2. The volume of each pallisade cell increased while air-space percentage decreased with decrease of temperature. Pallisade tissue consisted of two layers of cells, being about twice as thick as spongy tissue and this situation was little affected by the treat-ments. 3. The mean area of epidermal cell was greatest at the intermediate temperatures, becoming smaller as temperature increased or decreased. It was greater under long day than under short day. Stomatal density was high at abaxial surfacc and low at adaxial surface, and the density of the latter increased with increase of temperature although that of the former changed a little. The mean length of guard cell parallelled the mean epidermal cell size. The total guard cell length of both leaf surfaces per unit leaf area increased with increase of temperature. 4. TAC concentration, TAC content per unit leaf area increased with decrease of temperature, and were greater under long day. Crude protein concentration, on the contrary, decreased with decrease of temperature and was smaller under long day, although its content increased with decrease of temperature and was greater under short day. 5. The diameter of petiole was greater under long day and greatest at 30/25°C. The number of large and intermediate vascular bundles of petiole changed little by the treatment, but that of small bundles increased with increase of temperature. The petiole diameter and mean area of large vascular bundles were intimately related to leaf area. 6. The starch deposit in the chloroplasts increased with decrease of temperature, especially abundant in the spongy tissue. Under low temperatures, large peculiar compound starch grains were stored in the parenchymatous cells of petiole and stem. 7. Anatomical features affected by temperature and photoperiod did not show significant correlations to NAR, although SLW, leaf thickness, nitrogen content and Sol-N/Total-N ratio had negative correlations with NAR. 8. SLW had positive correlations with both leaf thickness and TAC concentration, a negative correlation with air-space percentage. 9. The growth parameters such as RGR, RLGR, LAR and NAR were all positively correlated with the mean ambient diurnal temperatures, and the correlation coefficients were higher for RGR, RLGR and lower for NAR.