Growth and Development of Alfalfa Plant under Controlled Environment : III. The effects of photoperiod and temperature on the growth and anatomical features of photosynthetic tissues

[摘要] A clone of alfalfa cv. Du Puits was grown under 3 photoperiods (8, 12, 16 hr in 1965; 12 hr in 1970) combined with 4 temperatures (day-night; 30-25, 25-20, 20-15, and 15-10°C) to determine the effects of these environmental factors on the growth and anatomical characteristics of photosynthetic tissues. Under shorter day and lower temperatures, the leaf/stem ratio and nitrogen concentrations of the both organs were higher as compared with those of longer day and higher temperatures. The leaf expansion rate decreased as temperature decreased. The leaf size was greatest at 20° or 25°, and smallest it 15° under short photoperiod. In general it became larger as photoperiod increased. The leaf thickness and intervein distance increased as temperature decreased. The mean epidermal cell area was greatest at 20°, becoming smaller at higher of lower temperatures. Stomatal density was smallest at 20°, greatest At 30°, while stomata index changed little. Pallisade cell number per unit leaf area increased with a smaller diameter and length as temperature increased. Leaves of plants grown at 20° had the largest intercellular spaces, followed by those grown at 25°, 30°, and 15° in order. The stem diameter was greater under longer photoperiod, and greatest at 20°. The stem chlorenchyma increased in thickness as temperature decreased. The amount of starches deposited at endodermis was greater at 20° or 25° under long photoperiod. RGR had the intimate correlations with both RLGR (relative leaf growth rate) and NAR in 1970 experiment with a small change of developmental phase by temperatures under a definite photoperiod (12 hr), while in 1965 experiment where much developmental change occurred under different photoperiods of longer duration thah in 1970, the correlation with NAR became weaker, although the correlation with, RLGR was still strong. In the regime of the experiments, the total plant weight was highest for plants grown at daily mean temperature around 20° (day-night, 20-15°or 25-20°) under long photoperiod, due probably to the largest leaf area per plant (largest RLGR) with the highest expansion rate and the largest size of leaf, being composed of the largest cells and intercellular spaces with a relatively high nitrogen concentration and a smaller respiration loss, all these resulting in a higher NAR.

[学科分类] 农业科学（综合）