Analysis of the Growth in Forage Crops : 3. Effect of temperature on organ formation in Ladino clover with special reference to photosynthetic organ formation

In order to investigate the effect of temperature on leaf production and transformation of photosynthetic product into various organs, the studies were carried out under both controlled environmental conditions and natural field condition. Obtained results are as follows: 1) Even without clipping, under higher temperature conditions, the growth of various organs decreases gradually, plants become weaker before long, and presents the symptom of summer depression. 2) The higher the temperature, the more the flower buds are formed, and the less the portion occupied by storage organs. And the preparations to regrowth become worse. 3) Becoming worse of preparations to regrowth under higher temperature conditions seems to be a result caused by adaptation to keep the balance between production and consumption. And as a result, the plants make their non-photosynthetic parts less relatively. 4) Maximum leaf-size is found under 15°C and 20°C temperature conditions, and it is found that under higher or lower than this optimum conditions leaf-size becomes smaller. 5) Not only the interval of leaflet emrgence but also that of its death become shorter under higher temperature, longer under lower temperature, but the increasing rate of living leaf number shown by the ratio of the former and the latter reaches maximum at 20°C and 25°C, and becomes less at 15°C and 30°C in accordance with this order. 6) It is found that the number of branches and its increasing rate reach maximum under 15°C and 20°C, and under hither or lower than this optimum conditions they become less. Flower bud initiation is subject to stimulation by long day and high temperature conditions. 7) The higher the temperature, the shorter the number of days required to expand leaflet fully. 8) Judging from the above stated facts, the apparence that total leaf area of the plant under higher temperature conditions may be attributed to the following facts; (1) the size of leaflet under higher temperature conditions is smaller than that of under lower temperature, and (2) lower increasing rate of branches and higher initiating rate of flower bud under higher temperature conditions make the increasing rate of living leaf number less.