Effects of greenhouse cultivation on the photosynthetic characteristics and fruit quality of Actinidia arguta

Abstract: 【Objective】The market supply window of fresh Actinidia arguta fruit is short due to the short storage life, and the leaves and branches are easily affected by natural disasters such as frost damage under open field cultivation conditions, which may lead to a decline in leaf damage, fruit yield, and poor fruit appearance quality. Therefore, attention should be paid on these problems in the cultivation of A. arguta. Greenhouse cultivation is a common method of promoting early cultivation, which has been widely used in the world. In this paper, two A. arguta varieties were cultivated in greenhouse, the effects of greenhouse cultivation on plant growth, photosynthetic characteristics and fruit quality of A. arguta were analyzed.【Methods】In this experiment, the four-year-old A. arguta varieties Jialü and Kuilü were placed in the solar greenhouse of the facility culture of Jilin Agricultural University, and the control was plants grown in the germplasm resource nursery of A. arguta of the University. Photosynthesis indexes and chlorophyll fluorescence indexes of leaves were measured, and the differences in leaf structure, leaf stomata and fruit quality were observed.【Results】The light response curves of the two varieties in greenhouse cultivation were significantly lower than those in open field cultivation. Except for Ci, the three photosynthetic indexes, Pn, Gs and Tr, were significantly lower than those in the open field cultivation. The order of Pn in each cultivation environment was Jialü open field cultivation＞Kuilü openfield cultivation＞Jialü greenhouse cultivation＞Kuilü greenhouse cultivation. Under greenhouse cultivation conditions, Jialü Pnmax decreased by 28.16% and Kuilü decreased by 24.28% compared with open field. In particular, the LCP of Jialü in greenhouse was 15.13% higher than that in open field, while Kuilü was the opposite. The Rd value of Jialü under greenhouse cultivation increased by 4.64% compared with that under open field, and Kuilü decreased by 12.47% . The apparent quantum efficiency (AQY) of Jialü in greenhouse decreased by 5.32%, and that of Kuilü increased by 24.7%. After linear regression analysis of CO2 response, the CE values of the two varieties decreased significantly in greenhouse cultivation, and the ability to use low concentration of CO2 was low, the performance of Jialü and Kuilü in greenhouse is relatively consistent. The analysis of chlorophyll fluorescence induction kinetics curve showed that the relative variable fluorescence of Vj point and Vi point increased significantly, and the values of Vk, Vj and Vi increased significantly in greenhouse cultivation compared with open field cultivation. The analysis of PSⅡ reaction center showed that there was no change in ETo/RC under greenhouse cultivation, but the ABS/RC and TRo/RC values of the two varieties cultivated in greenhouse were significantly higher than those in open field. Although the light energy absorbed and captured increased, the light energy finally used for electron transfer was the same as that in open field cultivation, most of which was used for heat dissipation and other ways to make energy loss, which showed that DIo/CSm was significantly higher than that in open field cultivation. The observation of leaf structure showed that the leaf thickness of A. arguta cultivated in greenhouse decreased significantly, which was in line with the characteristics of plants in greenhouse. The thickness of palisade tissue was smaller than that of open field cultivation, while the thickness of spongy tissue was greater than that of open field cultivation. The significant decrease in palisade/spongy ratio was the root cause of the decrease in photosynthetic capacity mentioned above. The thickness of upper and lower epidermis was smaller than that of open field cultivation, which made leaves vulnerable to external environment damage with adaptability to adversity. The stomatal density of A. arguta leaves cultivated in greenhouse was significantly lower than that in open field. Stomatal opening ratio, stomatal length and stomatal area were lower than those in open field cultivation, which led to the decrease in leaf gas exchange efficiency in greenhouse. This was the secondary reason for the decrease in CE value and Pn value. The fruit quality results show that the fruit size and weight in the greenhouse were lower than those in the open field. The transverse and longitudinal diameters of Jialü fruit under greenhouse cultivation were 4.29% and 8.79% lower than those in the open field, respectively. The longitudinal diameter, lateral diameter and single fruit weight of Kuilü were 8.36%, 2.41% and 14.07% lower than those of the open field, respectively. Although the fruit size decreased, there was no significant difference in contents of soluble solids, soluble sugars and vitamin C but a significant increase in titratable acid content. Greenhouse cultivation advanced the maturity of the fruit by 70 days, advanced the sales time of A. arguta market, extended the supply period of fresh fruit market, and brought considerable economic benefits.【Conclusion】Under greenhouse cultivation conditions, the adaptability of the two A. arguta varieties to the environment was relatively consistent. Firstly, the leaf morphogenesis tended to shade leaves. Secondly, the activity of the donor side and the receptor side of the PSⅡ reaction center was lower than that of the open field cultivation, resulting in weaker ability of the leaves in the greenhouse to use strong light and low concentration of CO2 than that of the open field. Finally, the external quality of the fruit decreased to a certain extent, but the internal quality had no significant change.