Effects Of Potassium Nutrition On Key Enzyme Activities Of Sucrose Accumulation In Vegetable Soybean

Potass ium( K) fertilization is a key pr actice for vegetable soybean(Glyc ine max L. Merr.) production due to its effects on yield and seed sucros e content. However, the mechanism of enhanced seed sucrose content by K application is not clear. Pot exper iments were conducted w ith two vegetable soybean cultivars( Zhongkemaodou 1 and c.v. 121) treated w ith no potass ium fertilizer( K0), 120 kg hm-2 K( K1), 120 kg hm-2 K w ith additional foliar applic ation of 30 kg hm-2 of K2SO4( K2). The purposes of this r esearch were to examine the eff ects of potass ium nutr it ion on key enzyme activities of sucrose accumulation in differ ent parts of vegetable soybean dur ing reproductive stages and to reveal the relationship between potass ium nutr ition and sucrose metabolism in vegetable soybean. The results are as follows:(1) Potass ium accumulation in var ious parts of vegetable soybeans was increased by K fertilization, and was further increas ed by additional foliar K f ertilization. K application also increased soluble sugar and sucros e accumulation in leaf, pod shell and s eed of vegetable soybean, and additional foliar K fertilization further enhanced both soluble sugar and sucrose content.(2) With 120 kg·hm-2 K fertilizer at seeding, activities of sucrose phosphate synthas e(SPS), sucrose synthase(SS), ac id invertas e( AI) and neutr al invertas e(NI) in leaf were increas ed, while further K f oliar application had a additional effects in increas ing the enzyme activities. K fertilization increased the activities of SPS and SS synthes is activity but decreased the activities of SS decompos ition, AI and NI in pod shell fr om 6 to 8 weeks af ter f lower ing. K applic ation increased SPS and SS activities in seed, but had no significant effects on AI and NI activities.(3) 120 kg·hm-2 K f ertilizer at seeding s ignif icantly improved fr esh pod yield of vegetable soybean, while additional K f oliar applic ation increased fresh pod yield mor e. After K fertilization, the total increased pod number of zhongkemaodou 1 was signif icantly and pos itively correlated with the increas ed fr esh yield, and ther e was a negative corr elation between the standard pods number and increased fresh pod yield under K foliar application(P<0.05).