生育温度を異にするオーチャードグラスの葉の生育経過と収量との関係について

抄録

Orchardgrass seedlings were grown for about seventy days in the glass houses kept at four constant temperature levels of 15, 20, 25 and 30℃ in order to clarify the effects of temperature on the appearance and decay of a single leaf and their influences upon the total number and weight of the leaves borne on a main stem and a whole plant. These measurements were taken at the beginning of the treatments and after 18, 36, and 72 days. The results obtained were as follows: 1) The life span of a single leaf was longer under the lower temperature treatment. A leaf on the upper node of a main stem had the longer life span than the lower one (Table 2). The period from the early to the full decay of a leaf blade was longer under the condition of the higher temperature (Fig.1). 2) Leaf emerging rate on a main stem was promoted at 25℃ throughout the experiment and number of decayed leaves was advanced at 30℃ from beginning to the 22nd day of the treatment, but thereafter 25℃ surpassed it (Fig.3). 3) Mean weight of a single leaf was the heaviest at 25℃ among the treatments. The number of living leaves increased from beginning until 18th day on a main stem and until 36th day of a whole plant, and decreased thereafter. The total weight of leaves was maintained the highest at 25℃ and the lowest at 30℃ (Fig.3). 4) Total weight of whole leaves per stem consists naturally of the weight of a single leaf and the number of live leaves. The number of live leaves on a stem was affected by the life span or duration of a single leaf together with the rate of leaf appearance (Fig.2). Both the number of live leaves and the weight of a single leaf showed a similar trend to that of the total weight of leaves during the early stage, but the number of live leaves at the later stage showed difference from the total weight (Fig.3). 5) Figure 4 shows the relationships between the total weight of leaves and the number of live leaves or the weight of a single leaf. In this figure, all the measurements of each age are experessed as deviation percentages from the mean of values of the 4 temperature treatments. Correlation coefficient between the total weight of leaves and the number of live leaves was γ=-0.241 but between the former and the single leaf weight, it showed γ=0.939 in the case of the main stem. And in a whole plant, these were calculated as γ=0.157 and 0.734** respectively. (**means significance at 1% level of the probability.) 6) By these facts, it is concluded that the mean single weight of a leaf contributes more efficiently towards the total weight of leaves, and accordingly, towards the whole weight of a stem or a plant than the number of attached live leaves at the late vegetative stage of orchardgrass.