Effects Of Continuous Light And Intermittent Light With Different Frequencies On Growth, Photosynthesis And Fluorescence Of Cucumber Seedlings Using Lighting-emitting Diodes(LED)

Cucumber was one of important vegetables of facility cultivation in our country. With the development of facility agriculture, LED was widely used as cultivation light source in social production practice. This test studied on suitable ways for the growth, photosynthesis and fluorescent of cucumber seedlings to figure out the most appropriate range of frequency and duty ratio, achieving the goal of saving energy, good quality and high yield. The ratio of LED were red light: far red: green: blue = 3:1:1:1, with the duty ratio of 90%. The frequencies of light were continuous light(CK) and 0.1 Hz(T1), 100 Hz(T2), 100000 Hz(T3) of intermittent light. After 30 days of treatment, the results of the test were as follows:1. Different frequencies of intermittent light had influences on morphological indexes of cucumber seedlings. The plant height, stem diameter, leaf area of T1, T2, T3 were significantly greater than control group. The leaf area had significant difference between the groups, the leaf area of T3 treatment increased 64.4% than control group.2. Different frequencies of intermittent light could promote accumulation of matter of cucumber seedlings.3. Different frequencies of intermittent light could significantly increase the content of chlorophyll of cucumber seedlings. The content of chlorophyll of T1, T2, T3 were significantly higher than control group. The content of chlorophyll a, b, a&b of T3 treatment were the highest, respectively increased by 92.25%, 86.24%, 90.62% than control group. Chlorophyll a/b of different frequencies of intermittent light had no significant difference with control group.4. Different frequencies of intermittent light could increase net photosynthetic rate of cucumber seedlings. Net photosynthetic rate of T1, T2, T3 increased by 12.54%, 1.08% and 29.23% than control group. Net photosynthetic rate of cucumber seedlings were not significant between treatment groups, and T3 treatment was the highest.5. Different frequencies of intermittent light had certain influences on fluorescence of cucumber seedlings. The maximum quantum yield and non-photochemical quenching of T3 were significantly higher than control group. While photochemical quenching, actual photochemical efficiency and electron transfer rate of T3 had no significant difference with CK. T1 and T2 processing cucumber seedlings unless photochemical quenching q N were significantly higher than CK, chlorophyll fluorescence characteristics of the indicators had no significant difference with CK.To sum up, from the point of seedling morphological index, T3 treatment was suitable frequency for cucumber seedlings. From the aspect of material accumulation, T1 treatment was suitable frequency for cucumber seedlings. From the point of chlorophyll content and photosynthetic fluorescence characteristics, T3 treatment could increase the content of chlorophyll, light system Ⅱ maximum quantum yield and non photochemical quenching of cucumber seedlings, which was beneficial to the smooth progress of photosynthesis. Thus significantly increased the net photosynthetic rate. Due to the increase in net photosynthetic rate, plant height, stem diameter, leaf area and other morphological index increased, eventually lead to accumulation of seedling matter. Therefore, T1(0.1 Hz), T3 treatment(100000 Hz) were suitable frequencies for the cucumber seedlings.