The Effect Of Different Light Modes On Cucumber Seedlings Growth

Conventional light sources have been successfully used to cultivate a wide variety of horticultural crops.However,they are of limited use due to uncontrollability of spectra and energy inefficiency.LEDs emerged with tremendous potential in controlling environmental factors in agriculture due to their energy efficiency,longevity,and spectral specificity,but the effects of different types of LEDs and the different light intensities and combinations on plant growth and development are yet to be established.In this research we investigate the effect of different light modes on growth and development of cucumber seedlings.This paper took the cucumber(Cucumis sativus L.)as material.The plants were grown in a growth chamber at(25.0±18? 30 days after sowing,and data were subsequently collected.Three plants were chosen randomly from each treatment and checked growth,morphological and biochemical parameters.Cucumber seedlings were grown under nine different combinations of red and blue lights provided by LEDs and white light(WL)as control.Before the experiment,a set of LED plant chamber had been designed and assembled completely in which the light quality,light intensity and photoperiod were controlled separately with better Light uniformity to establish a solid foundation for the successful completion of the experiment.The results showed that growth and morphological parameters were optimal under combinations of red and blue lights with 150 ?mol m-2s-1 intensity compared to WL.Plant height,fresh and dry shoots and root,as well as diameter and Length of hypocotyl,were significantly higher compared to control condition WL.Root Length and Leaf areas were better developed under light intensity of 150 ?mol m-2s-1 than other tow intensities.Leaf number and area did not shown significant variation among all treatments as well as control WL;they increased with increasing light intensity.Water content showed decrease with increasing light intensity.Photosynthetic pigments showed variation in their absorbance at different light intensities and ratios of blue to red light.Chlorophyll a/b and carotenoid increased with increase in light intensity.In addition,chlorophyll a/b had their greatest absorbance at 7:3 blue to red light ratio at all the treatments and this increases with increase in the light intensity.We also assayed for the biochemical parameters of each treatment.We found that soluble sugar content increased by 23%,30%and 47%at light intensities of 80?mol m-2s-1,100 ?mol m-2s-1 and 150 ?mol m-2s-1,respectively.The concentrations of both nitrate and soluble protein contents were reduced significantly with increase in light intensity.It was concluded that higher light intensities are more beneficial and promoted plant growth and development better than the lower ones.The growth of the seedlings is more favorable at higher red to blue light ratios.Photoperiod had shown no significant effect among all the treatments.Our results are consistent with a previous study which established that the most suitable light ratio for cucumber plant is 30B:70R.