Effects of Shading on Photosynthetic Characteristics,Antioxidant Enzymes Activities and Starch Physicochemical Properties of Sweet Potato Shangshu 19

Ran Tengfei; Li Yongpeng; Yang Yuquan; Pan Shuheng; Tian Shanjun

doi:10.14083/j.issn.1001-4942.2025.04.008

Abstract：In this experiment,starch type sweet potato Shangshu 19 was used as the material,and shad-ing nets were used for shading treatments during the simultaneous growth period of vines and root tubers with natural light conditions as the control(CK).The effects of full-time shading(full shading treatment)and re-lighting after shading(relighting treatment)at the middle and later stages of growth on the photosynthetic characteristics,antioxidant enzymes activities,starch physicochemical properties and dry matter accumulation of Shangshu 19 were studied.The results showed that during the T3 period(about 130 days after transplanting seedlings),the number of leaves per plant in both full shading and relighting treatments were higher than that in CK,which reached significant level under full shading treatment;the leaf area per plant under full shading treatment was significantly higher than that of CK,while that was significantly lower under relighting treat-ment;no significant differences were detected in the other plant trait indicators among the treatments.During the T2 period(about 90 days after transplanting seedlings),the ratio of SPAD to leaf specific gravity of sweet potato leaves in full shading and relighting treatments were very significantly lower than that of CK,while that was slightly lower than CK during the T3 period with no significant difference.During the T3 period,the net photosynthetic rate(Pn),intercellular carbon dioxide concentration(Ci)and transpiration rate(Tr)of sweet potato leaves inboth full shading and relightingtreatments were significantly lower than those of CK.During the T2 and T3 periods,the maximum fluorescence(Fm)and the minimum fluorescence(Fo)of sweet potato leaves in full shading and relighting treatments were higher than those of CK,while the non-chemical quench-ing coefficient(NPQ)was very significantly lower during the T2 period but very significantly higher than that of CK during the T3 period.The activity of peroxidase(POD)in the leaves of full shading treatment was very significantly higher than that of CK during the T2 and T3 periods,and that of catalase(CAT)was very signifi-cantly higher than that of CK during the T3 period.The surface of the starch granules in the root tuber of Shan-gshu 19 under shading treatments was rough with obvious wear and corners,and the average particle size de-creased.Shading treatment increased the light transmittance and water separation rate of starch in the root tu-bers of Shangshu 19,and reduced the hardness,cohesiveness,elasticity and adhesiveness of starch.These conclusions could provide certain data supports and theoretical bases for sweet potato production and processing in low-sunshine areas.