Differences of the stomatal conductance, transpiration rate and net photosynthesis rate between F₁s and their parents in sugar beet（Beta vulgaris ssp. vulgaris）

Abstract

　To investigate the effect of surface temperature (T_c) differences and to clarify the plant physiological differences between F₁s (F₁：First filial generation) and their parents, we analyzed the differences of the stomatal conductance (g_s), transpiration rate (E) and net photosynthesis rate (A) among six sugar beet genotypes.
　Three of the genotypes: “NK195BR”, “NK235BR” and “NK388” were tested as parents, while the other three “NK235BR×NK195BR”, “NK195BR×NK388” and “NK235BR×NK388” were tested as F₁s. From the comparison of the mean T_c value of six genotypes measured at 6 hours (from 10:00 to 16:00), the results, in descending order of their value, showed “NK235BR” > “NK388” > “NK195BR” > “NK195BR×NK388” > “NK235BR×NK195BR” > “NK235BR×NK388”.
　To analyze the relationship between T_c and plant physiology, g_s, E and A were measured at six times during mid-growing season. As a result, g_s and E had a significant varietal difference among the six genotypes every measurement. Both the g_s and E values of F₁s had a trend higher than those of their parents. A comparison between g_s and the differences between T_c and air temperature (ΔT), revealed that the two had a negative liner correlation such that the higher the g_s was, the lower the ΔT. On the other hand, A had a significant varietal difference depending on the day. However, there was no clear relationships to indicate that F₁s had a trend higher than those of their parents.
　In relation to yield component and plant physiological properties, root weight and sugar yield were significantly correlated with both of g_s and E and had no significant correlation with the sugar content. On the other hand, A had no significant correlation with root weight, sugar content or sugar yield.