Effect of magnesium on growth and photosynthetic carbon metabolism in apple plant under high potassium contions
This experiment was carried out to study the effects of different magnesium levels(0.1,3,and 6 mmol·L-1)on apple dwarfing rootstock G935 seedlings growth and photosynthetic carbon metabolism un-der suitable(6 mmol·L-1)and high potassium(18 mmol·L-1)conditions,using 13C isotopic tracer technolo-gy,and conducted under hydroponic conditions.The results showed that high K treatment significantly re-duced the net photosynthetic rate of leaves and carbon metabolic enzyme activity,inhibited the allocation of photosynthetic products to the root system,and inhibited plant growth compared to suitable K treat-ment.In contrast,adding Mg alleviated the inhibition of high K on apple plant growth,compared to the K18Mg0.1 treatment,the apple seedlings'biomass weight increased by 55.69％and 66.45％under the K18Mg3 and K18Mg6 treatments,respectively.Under high K conditions,Mg significantly increased Pn,Gs,the light energy capture ability and photosynthetic electron transport capacity.Compared to the K18Mg0.1 treatment,Pn,Gs,Fv/Fm and ΦPSII in the K18Mg6 treatment increased by 204％,159％,12.67％and 36.44％,re-spectively.Under high K conditions,as the Mg supply level increases,the activities of 6-phosphoribosyl de-hydrogenase(S6PDH),sucrose synthase(SS),and sucrose phosphate synthase(SPS)gradually increased,the accumulation of 13C also intensified with the boost in magnesium supply level,and magnesium signifi-cantly promoted the transportation of 13C photosynthetic products from leaves to roots In summary,provid-ing magnesium under high potassium conditions enhances the net photosynthetic rate of leaves,increases the accumulation of photosynthetic products,and facilitates the distribution of photosynthetic products to roots.This ensures an adequate supply of energy and carbon skeletons for root growth and development,ultimately alleviating the growth inhibition imposed by high potassium on apple plants.
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