さし穂の光合成に関する研究 (第2報)

Abstract

To study the role of photosynthesis in rooting of the cuttings during propagation, changes in the rate of apparent photosynthesis after planting were investigated in relation to some other factors. Five plants, viz. Camellia japonica L., Camellia sasanqua Thunb., Viburnum awabuki K. Koch, Forsythia suspensa Vahl. and Chrysanthemum morifolium Ramat. were used for these experiments. The rate of apparent photosynthesis was determined by measuring the quantity of CO2 using an infrared gas analyzer.1. Time courses of the rate of apparent photosynthesis after planting for the above five plants showed a similar tendency, i. e. the rate declined temporarily immediately after planting. However, the extent was much grater in Forsythia suspensa Vahl. and Chrysanthemum morifolium Ramat. which are easy to root.2. The effect of light intensity on the rate of apparent photosynthesis was investigated at different stages of propagation with the cuttings of Camellia japonica L., Forsythia suspensa Vahl. and Chrysanthemum morifolium Ramat. In general, the rate was greatly stimulated as the intensity was increased to reach a maximum at about 20 klux, and after that it began to decline.3. To clarify the relationship between the change in the rate and the number of leaves per cuttings, the rates were measured periodically at various stages of propagation with the respective cuttings of Camellia sasanqua Thunb. having one, two and three leaves and those of Viburnum awabuki K. Koch having one, two and four leaves. Almost on difference in the rate was found among those cuttings at the time of starting, while a remarkable decline occured after planting in 3- and 4-leaf cuttings rather than in 1- and 2-leaf cuttings. When compared on the basis of a whole cutting, the rates showed a proportional relation of the number of leaves. A marked decline was also recognized in 3- and 4- leaf cuttings.4. Canges in water content in the leaves of the cuttings of the five plants showed a similar tendency to those of apparent photosynthesis. The chlorophyll content in the leaves of the cuttings of Camellia japonica L. continued to decrease gradually during propagation.