Abstract:

High oil corn is a value-added corn type，which contains more oil and higher quality protein than normal corn. At present high oil corn has not been widely planted by farmers because its grain yield is lower than that of normal corn. The yield of high oil corn is restricted by lower net photosynthetic rate. A field experiment with a planting density of 30 000 plants ha^-1 was carried out to reveal the reason of lower net photosynthetic rate of high oil corn. The technique of chlorophyll fluorescence was used to measure light energy utilization efficiency of high oil corn. Light energy utilization and dissipation of upper, middle and basal leaves of high oil corn 115 in grain filling stage was studied. Compared with ND108，net photosynthetic rate (P_n), transpiration rate (T_r), stomal conductance (G_s) of were significantly lower（P<0.05）; intercellular CO₂ concentration (C_i) and water use efficiency of HOC115 (WUE) were slightly lower in ND108 (P>0.05). PSⅡ maximal photochemical efficiency (F_v/F_m) of HOC115 was lower significantly than that of ND108. PSⅡ activity (F_v/F_o) of HOC115 was slightly lower than that of ND108 (P>0.05). Apparent relative electron transportation rates of HOC115 were lower than that of ND108. Compared with ND108, the proportion of light energy used in heat dissipation by HOC115 was higher when light energy was constant. This result indicated that light energy utilization efficiency of HOC115 is lower than that of ND108. The largest light utilization efficiency difference between HOC115 and ND108 was observed in middle leaves. In conclusion, photosynthetic rate of HOC115 is lower mostly due to lower light energy utilization efficiency. In high oil corn breeding and cultivation, we should select high photosynthetic inbred lines and improve the growing conditions with suitable fertilizer and irrigation to enhance their light use efficiency.

Key words: High oil corn, Light energy utilization, Light energy dissipation, Grain filling stage