| To find a suitablelight environment for growth of garlic shoots, the photoperiods with short lighting of 12 hours and long light of 18 hours were used to study their effects on growth, photosynthetic characteristics and sucrose phosphate synthase (SPS) activity of garlic seedlings. Under each short hours and long hours group, there were 4 different light quality treatments of white, blue, red and dark and their combinations: 12 hours LED white light/12 hours dark (12W/12D), 6 hours LED white light+6 hours LED red light/12 hours dark (6W+6R/12D), 6 hours LED white light +6 hours LED blue light/12 hours dark (6W+6B/12D), 6 hours LED white light+6 hours (LED red light+LED blue light)/12 hours dark (6W+6 (R+B)/12D) , 18 hours LED white light/6 hours dark (18W/6D), 6 hours LED white light+12 hours LED red light/6 hours dark (6W+12R/6D), 6 hours LED white light+12 hours LED blue light/6 hours dark (6W+12B/6D), and 6 hours LED white light+12 hours (LED red light+LED blue light)/6 hours dark (6W+12 (R+B)/6D). (1) Compared with shorter lighting photoperiod, longer lighting photoperiod reduced leaf length, pseudostem lenfgth and Ci by 17.66%, 16.38% and 20.38%, respectively (P<0.05), and 18W/6D reduced them by 25.88%, 27.12% and 35.25%, respectively.On the contrary, longer lighting photoperiod significantly increased leaf width by 11.19% (P<0.05), but it was independent of light quality. Longer light photoperiod also increased the value of the fresh weight of pseudostem and leaves, chlorophyll content (SPAD), chlorophyll minimum fluorescence intensity (Fo), maximum yield of PSⅡ (Fv/Fm), potential photochemical efficiency (Fv/Fo), net photosynthetic rate (Pn) and sucrose phosphate synthase (SPS) activity by 20.70%, 8.55%, 11.27%, 8.64%, 7.91%, 118.07% and 43.65%, respectively (P<0.05). Of which 6W+12(R+B)/6D had the largest increase (P<0.05), increasing 40.37%, 19.16%, 19.32%, 19.75%, 26.37%, 192.90% and 84.04%, respectively. (2) Compared with pure white lighting photoperiod, other photoperiods significantly increased Gs value and the activities of and Rubisco in leaves (P<0.05), and 6W+12 (R+B) /6D had the greatest increase. Compared with 12W/12D, 6W+12 (R+B) /6D increased Gs value and the activities of Rubisco by 96.56% and 230.56%, respectively. Compared with 18W/6D, 6W+12 (R+B) /6D increased Gs value and the activities of Rubisco by 94.54% and 221.62%, respectively. (3) Compared with 12W/12D, other photoperiods significantly increased pseudostem diameter (P<0.05), and the mean value was 1.17 times that of 12W/12D, but there was no significant difference among photoperiods (P>0.05). These results indicated that long light irradiation inhibited the growth of pseudostem and leaf, [JP2]but promoted the growth of stem thickening and increased the fresh weight of pseudostem and leaves. Blue and red light significantly promoted the growth, photosynthetic characteristics of leaves, and Rubisco and SPS related formation and transport of photosynthate. The combination of blue and red light had synergistic effect. The synergistic effect of longer blue and red lighting was more noticeable. |