Effects of pink fluorescent filming and pink netting on the photosynthetic characteristics and fruit quality of ‘Shine Muscat' grape

Abstract: 【Objective】The objective of the study was to elucidate the effects of selected light technique onthe photosynthetic characteristics and fruit quality of‘Shine Muscat'grape. Selected light technique is ap-plied to maximize crop photosynthesis,which had been studied by researchers in Tokyo University,Ja-pan. Because plants need short wavelength(245 nm) for photosynthesis,they used polymeric fluorescentdyes to enhance the effect of red wavelength on photosynthesis. In this experiment,we used the pink fluo-rescent film or pink net cover to change the light quality in greenhouse,and observed the effect on thephotosynthetic characteristics and fruit quality of‘Shine Muscat'grape.【Methods】The experimental ma-terials were five-year-old vines of‘Shine Muscat'grape,which were planted in a greenhouse. On bothsides of the rain shelter,small arch sheds were set up. The sheds were covered with pink fluorescent filmor pink net as the treatments,and the greenhouse with no shed as the control(CK). Photosynthetic andphysiological indexes including net photosynthetic rate(Pn),stomatal conductance(Gs),transpirationrate(Tr),intercellular CO2concentration(Ci) of the exposed middle leaves(the 6th or 7th blade) in differ-ent growth periods(at blooming from May 5 to 7;young fruit stage from June 15 to 17;the second berryexpansion period from July 25 to 27;and berry mature stage from September 1 to 3) were measured with aLi-6400 photosynthetic system on sunny days from 9: 00—11: 00. During the measurements,flow rate was set at 500 μmol·m-2·s-1,light intensity ranged from 0-2 000 μmol·m-2·s-1(0,20,50,100,200,400,600,800,1000,1 200,1 600 and 2 000 μmol·m-2·s-1). The effects of the treatments on fruit qual-ities,such as the fruit length,width,fruit weight,soluble solids and titratable acids were examined.From August 10,30 berries of moderate size from every cluster were sampled randomly every 5 days.Length and width of grape fruit were measured with an electronic digital caliper,and a 1/100 g electronicbalance was used to obtain fruit weight. Determination of soluble solid content was carried out with ahand-carried RA-250 reflectometer,and titration method was used to measure titratable acid content.【Results】The changes of Pn with light intensity fitted well with corrected rectangular hyperbole model. Asthe light intensity increased,the change trends of photosynthetic rate in different treatments at the samestages and in different stages under the same treatments were different. From the change trends in the fourstages,the photosynthetic rate was in the order of pink fluorescent film > pink net > CK,and the photo-synthetic rate in the same treatments increased gradually with time. Pink fluorescent filming and pink net-ting treatments improved the photosynthetic capacity of grape leaves,and thus were favorable for the pho-tosynthate accumulation. The trends of stomatal conductance and transpiration rate were consistent withphotosynthetic rate,while the intercellular CO2 concentration in the treatments of pink fluorescent filmingand pink netting were lower than the control at all stages. In comparison with the control,filming and net-ting also increased fruit length by 3.53% and 4.16%,diameter by 9.74% and 10.33%,and fruit weightby 9.72% and 10.33%,respectively. The treatments had impacts on fruit sugars and acids. The contentsof soluble solids in filming and netting treatments were higher than the control in the early stages,but hadno significant difference in the late stages,while an opposite trend was observed in the contents of titrat-able acids,which were lower in the filming and netting treatments than the control in the early stages butbasically the same in the late stages. In addition,the treatments could advance fruit maturation. Therewas no significant difference in fruit quality between filming and netting treatments,both of which signifi-cantly increased fruit quality compared with the control.【Conclusion】In conclusion,pink film cover andpink net cover treatments increased photosynthetic rate and stomatal conductance in‘Shine Muscat'grape. During the same periods,net photosynthetic rate in pink filming treatment was the greatest. As theberry matured,leaf photosynthetic rate increased until full maturity,and it was similar during the berrygrowth periods. In addition,pink filming and netting increased fruit weight,longitudinal diameter,trans-verse diameter and other fruit quality indexes. Effects of pink fluorescent filming and pink netting werenot significantly different. Changes in light quality have significant impact on photosynthesis characteris-tics as well as their growth in fruit trees. Through the simple method of changing light intensity and quali-ty,photosynthesis and fruit quality can be improved. Thus,selected light technique has a significant rolein improving photosynthetic capacity,fruit growth and quality of‘Shine Muscat'grape,and may be ap-plied to other fruit trees.