Effect of Daily Light Integral on the Growth, Photosynthesis and Chlorophyll Fluorescence of Cucumber Plants in Pot Soil Culture

Light is a crucial factor in crop cultivation.This study aimed to determine the effect of daily light integral (DLI) on the growth of cucumber plants, physiological response, irrigation amount and soil water tension (SWT) in pot soil cultivation.Seedlings were grown in pots filled with soil and treated under three different DLIs at 2.88, 11.52 and 20.16 mol m -2 d -1 indicated L S, L M and L H respectively) for three weeks.It was applied using white LED (light-emitting diode) light.The results showed that the leaf area and shoot's fresh and dry weights of plants were significantly higher in L M -treated plants than those grown in L S and L H treatments.In addition, plant height, root surface area and SPAD value were lowest in plants grown in L S treatment.There was no significant variation in number of nodes and stem diameter of plants among the treatments.The photosynthesis rate was higher in L M (4.34 mol CO 2 m -2 s -1 ) and L H -treated (4.81 mol CO 2 m -2 s -1 ) plants than in L S (0.92 mol CO 2 m -2 s -1 ).However, the concentration of intercellular CO 2 in leaves was higher in L S -treated plants.Plant stomatal conductance, transpiration rate and the F v /F m (maximum quantum yield of photosystem-II) ratios were not significantly different between the treatments.Furthermore, total irrigation volume in different treatments was varies with DLI values and it was highest in L H treatment (10.2 L/plant).SWT was not significantly different between the treatments L S and L M but observed low pressure in L H treatment.The principal component analysis (PCA) illustrated leaf area, shoot fresh weight, photosynthesis rate and stomatal conductance of plants has a positive correlation.These results suggest that at the initial stage of cucumber plants, daily light integral 11.52 mol m -2 d -1 was preferable for their growth and development and worthwhile based on irrigation amount than other treatments.