Effects Of ASIT On Physiology And Biochemistry Of Grafted Hickory Seedlings Under Shade

At present,the ecological environment has changed drastically on a global scale,and the original ecological environment of plants has been affected to varying degrees.hickorys are facing ecological problems such as increased pure forestification and continuous cloudy days in the planting area during the peak growth period.However,the energy necessary for its growth is directly or indirectly derived from light energy.Insufficient light leads to the growth of plants and the decline of plant resistance.And other phenomena.Mitigating the adverse effects of insufficient light on plants and enhancing their ability to adapt to the environment is an issue that needs to be paid attention to in hickory cultivation.Anti-hydrolyze Stabilized Ionic Titanium(ASIT),which has been widely used in agriculture and forestry in recent years,has the effect of enhancing stress resistance.When the hickory grafted seedling plants lack sufficient solar radiation,it has not been reported whether the foliar spray of ASIT can alleviate the adverse effects.The grafted combination seedlings of hickory(Scion/root-stock:C/C,C.cathayensis/C.cathayensis;C/H,C.cathayensis/C.hunanensis;C/I,C.cathayensis/C.illinoensis)and seedlings(C,C.cathayensis)were used as test materials,and different shade degrees(N,shading rate is 0%;S1,shading rate is50%±5%;S2,shading rate is 90%±5%)and ASIT treatments were performed to observe the plant phenotype and chloroplast ultrastructure changes,and to determine and analyze the dynamic changes of physiological indicators during the treatment period.The results are as follows:1.With the increase of shading degree and the extension of treatment time,grafted hickory seedlings showed the phenomenon of leaf edge folds and defoliation.The content of relative water content(RWC)and malondialdehyde(MDA)increased,the content of ribulose 1,5-bisphosphate carboxylase/oxygenase(Rubisco)decreased,and the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased.Among them,the POD activity of C/C,C/H,C/I and C leaves increased by 18.06%,5.12%,13.30%and40.81%,respectively.The CAT activity of C/C was most affected by S2 treatment,and reached the highest value on the 30th day of treatment.46.52 U·g-1·min-1 FW.At the same time,shading decreased the net photosynthetic rate(P_n)of grafted seedlings,increased photochemical efficiency of PSII(Fv/Fm),and decreased non-photochemical quenching(NPQ)and electron transport rate(ETR).Except for C/H,the total soluble sugar content of other seedlings showed a trend of S2<S1<N;the starch content of C/C and C accumulated in S1 and was consumed in S2.C/H was most affected by S2 treatment,S2 was more than N Reduce by 3.45%.Compared with N,the transpiration rate(T_r),photosynthetic rate(P_n)and stomatal conductance(g_s)of S2 had significant differences on the 30th day of treatment.S2 shading caused severe damage to the chloroplast structure and even inhibited the growth of seedlings.It shows that the sensitivity and response to shading between the same root-stock and different scion combinations are different,and heavy shading S2 has the greatest impact on C/H.2.The content of leaf mass per area(LMA)and chlorophyll content(Chl)in hickory grafted seedlings treated with ASIT foliar spray increased.After spraying ASIT,the specific leaf weight of C/H and C/I was significantly higher than that of the unsprayed group under the same S2 conditions,increasing by 67.3%and 111.4%,respectively.The Rubisco content and Pn under shade conditions were most significantly affected by ASIT treatment on the45th day.Compared with seedlings without ASIT treatment,ASIT increased NPQ,ETR,POD,CAT activity,and non structural carbohydrate(NSC)content.Among them,the starch content of C/I under light shading treatment was most affected,and S1+T was 3.12%higher than S1.The starch content of S2+T of C/H is 5.10%higher than that of S2.In addition,ASIT reduced the MDA content and SOD activity of grafted seedling C most significantly,reducing 27.54%and 36.80%,and had no significant effect on Fv/Fm.In S1,ASIT has a greater enhancement effect on C/I Tr and gs,while under S2 conditions ASIT has a greater enhancement effect on C/C and C/H Tr and gs.Spraying ASIT under light shade S1 has the greatest impact on Ti accumulation in plant roots and leaves.3.After comparing the phenotypes and physiological indicators of the three grafted combination seedlings and one seedling under shading treatment,it was found that the grafted seedlings of different root-stocks had different resistance to shading stress,where C/H is the most affected,C is the second,and C/I is the strongest.Moreover,the effects of spraying ASIT are related to the selected root-stocks,among which ASIT has the weakest alleviating effect on C/H.The above results indicate that heavy shading will have an irreversible negative effect on plants,and leaf application of ASIT can promote the ability of hickory grafted seedlings to resist shading stress to a certain extent.It shows that ASIT can be used as a potential relieving agent to improve plant growth in the short term.However,due to the timeliness of ASIT,its impact on photosynthetic characteristics is limited.