Effects Of Low Light Environment And LED Red And Blue Light Supplement On Growth And Development Characteristics Of Tomato

"Harvest 74-560 RZ F1" tomato cultivar was cultivated in a plant factory with LEDs.One stage selected from the four reproductive stages that were flowering stage,expanding stage,color turning stage and harvesting stage was subjected to low light intensity of 160 μmol·m-2·s-1,meanwhile,the light intensity at unselected stages in the same treatment maintained 1000μmol·m-2·s-1.The light intensity kept 1000 μmol·m-2·s-1 at all the reproductive stages in the control.The sensitivity of tomato to low light at different developmental stages was evaluated by growth and fruit quality indexes,and the experimental results would indicate the most sensitive developmental stage of tomato to low light.Then,the effective light supplement formula of red and blue light quality[red(R),blue(B)]after weak light treatment was further investigated during the weak light sensitive period of tomato.The experiment set up four red blue quality formula red:blue=10R0B,red:blue=9R1B,red:blue=1R1B,red:blue=1R4B to explore the relationship between red blue quality and growth characteristics of tomato.The results of this study will provide theoretical and technical guidance for the regulation of light environment in greenhouse tomatocultivation.The test results show that:(1)Low light at flowering stage or fruit expansion stage had a significant effect on the morphological structure of tomato plants.Low light at these two development stages also significantly delayed the development process of tomato plants and fruit harvest time,which were most prominent under flowering stage treatment.Flowering after the weak light of the first and second spike fruit longitudinal/transverse diameter ratio than other small processing,fruit shape tends to flat,and the first three fruit number,fruit rate is not high,the flowering weak light significantly reduced the first ear fruit number and fruit rate,and fruit enlargement period the weak light of dealing with the ear of the first fruit enlargement inhibitory effect is more apparent,As a result,the final yield of flowering stage and fruit expansion stage decreased significantly compared with other stages.Compared with the control,low light treatment increased the water content and decreased the soluble solid content of tomato fruit at different stages,and this change was more obvious under flowering treatment.Compared with the control,the soluble sugar content of tomato fruits decreased by 15%and total acid content increased by 26%after low light treatment,resulting in the lowest sugar-acid ratio of tomato fruits under this treatment.Low light treatment increased the value of reducing sugar/sucrose(H/S)and significantly decreased the content of ascorbic acid in tomato fruits during the four growth stages,and the H/S value was the highest and the content of ascorbic acid was the lowest in tomato fruits after low light treatment at harvest stage.Above all,weak light at different stages of tomato growth and fruit quality are different,the influence of weak light not only influence the quality of tomato,blooming also inhibit the growth of the tomato plant morphological structure rationalization and biomass accumulation,significantly reduce the fruit yield,and the weak light in the other stages mainly affected the quality of tomato fruit.According to the comprehensive effects of low light at four developmental stages on various growth physiological indexes of tomato,light environment regulation at flowering stage is an important period to reduce or avoid low light production loss of greenhouse tomato.(2)After low light stress at flowering stage,red and blue light quality supplement promoted the accumulation of tomato biomass.Among them,10R0B treatment accelerated the vertical growth of tomato plants,reduced stem diameter and internode elongation,while 1R4B treatment was the opposite,while 9R1B treatment was between 10R0B and 1R4B,and the leaf area was the largest at the late treatment.In addition,chla and chl(a+b)contents in tomato leaves under 9R1B irradiation increased significantly at the later stage of treatment,while the content of chla and chl(a+b)in tomato leaves under 10R0B irradiation was lower.When the ratio of blue light was 1R4B or 10R0B,the conversion of primary light energy and the potential activity of PSII reaction center were suppressed with the increase of treatment days,while when the ratio of blue light was 9R1B,the damage of photosystem II of tomato leaves could be avoided.At the same time,red and blue light supplementation could promote fruit development,which was most prominent under 9R1B treatment.Compared with normal light restoration,red and blue light supplementation increased the number of flowering and fruit setting and fruit setting rate of the second and third panicle fruits,and 1R4B treatment had the best recovery effect.In conclusion,reasonable red and blue light quality supplement measures have positive effects on reversing low light stress injury in greenhouse tomato cultivation.