Effects of different light quality on growth, photosynthetic characteristic and chloroplast ultrastructure of upland cotton (Gossypium hirsutum L.) seedlings

Abstract

The objective of the present study was to evaluate the effects of different light emitting diodes (LEDs) on growth, photosynthetic characteristic and chloroplast ultrastructure of upland cotton (Gossypium hirsutum L.) seedlings. Seedlings of the cultivar Sumian 22 were grown under seven different lights including blue (B) plus red (R) LEDs BR (1:8, 1:3, 1:1, 3:1), B LEDs, R LEDs, fluorescent lamps (FL) with the 100 μ mol m-2 s-1 photosynthesis photon flux (PPF), a 12 hour photoperiod for 40 days. Compared with FL, fresh mass, dry mass, root length, stem width, root activity, length of palisade tissue, stomatal frequencies were significantly greater as well as the thickest grana lamella in chloroplast in seedlings grown under BR1:8 LEDs; The chlorophyll a, chlorophyll b and total chlorophyll contents, photosynthetic rate, leaf thickness, spongy tissue length and stomatal areas were highest in seedlings under B LEDs; The stem length, leaf area, sucrose, soluble sugar, starch concentrations were highest as well as the greatest number, volume of starch grains in chloroplast in seedlings under R LEDs. It was suggested that BR1:8 LEDs might be used as a primary light for the cultivation of upland cotton seedlings under controlled conditions.