Studies on the Dry Matter Production of Sweet Potato : VII. Varietal differences of photosynthesis and factors concerning with photosynthetic rate.

Abstract

The same four varieties of sweet potato as reported in the previous paper, were used to investigate some aspects of varietal differences of photosynthesis and factors concerning with photosynthetic rate. 1). There was a varietal difference of photosynthesis per pot between Norin No. 1 and Okinawa No. 100. The photosynthesis of Norin No. 1 was mainly supported by having broader leaf area than other varieties, and Okinawa No. 100, having the smallest leaf area among the four varieties, showed higher photosynthesis per unit leaf area than others. Consequently, both Norin No. 1 and Okinawa No. 100 showed similar rates in photosynthesis per pot at the first half of their growing stages. 2). The results obtained in the relation between photosynthetic rate per unit dry leaf weight and the three major nutrient elements in the leaves essentially agreed with those described in the previous paper. It was shown that both potassium and nitrogen closely correlated to photosynthetic rate, and carbohydrates concentration in leaves showed high negative correlation for photosynthetic rate. All positive correlation factors for photosynthetic rate, i.e. nitrogen, potassium and respiratory rate of leaves, had respectively negative correlation for carbohydrates concentration in leaves (See table 2).