| By field experiment and greenhouse simulate cultivation are combine with lab analysis we studied the effects of boron on yield, quality and growth among four sweet potato cultivars(SS19,Q Z1,YS25 and LS9). The results showed that:1. In a certain range of boron, applying boron could increase the yield of sweet potato, but increasing effect was different among four cultivars. The yield- increasing effect of QZ1 was the highest compared with the control, which was up to 48.32%, while SS19 was 31.25%, YS25 was 26.48% and LS9 was 17.23%. Excessive boron not only decreased sweet potato yield, but also produced boron poisoning in leaf. Under this experiment condition, the optimum concentration of boron on fresh-eating sweet potato YS25 and LS9 was 15 kg·hm-2, while starch-type sweet potato SS19 and QZ1 was 7.5 kg·hm-2. 2. Appropriate boron content could increase fresh weight per plant of sweet potato, under the condition of optimum boron content, the fresh weight per plant of YS25 increased 24.09 g, SS19 and Q Z1 increased 102.40 g and 126.78 g respectively. Appropriate boron content could increase the proportion of commercial sweet potato weighed between 200 g and 500 g. Under the condition of optimum boron content, the proportion of commercial sweet potato which weighed between 200 g and 500 g increased 8.39% in SS19, 4.82% in QZ1 and 6.92% in LS9 respectively. 3. There were differences between different varieties of sweet potato because of applying boron, which affect the starch and soluble sugar content in root.Applying boron could increase starch content and reduce soluble sugar content of YS25 and SS19 in a certain range of boron, promote soluble sugar changing into starch of YS25 and SS19. Under the condition of optimum boron content, the starch content increasing amount of YS25 was highest compared with the control, which had up to 8.03%; SS19 was second, increased by 3.08%; The soluble sugar content of YS25 and SS19 reduced 6.25 mg·g-1 and 10.80 mg·g-1 respectively. Applying boron could increase starch content and soluble sugar content in root of Q Z1; But the effect on quality promotion of LS9 created by boron was insignificant and the starch and soluble sugar content was slightly cut down. Applying boron could increase soluble protein content in sweet potato root. The increasing amount of SS19 was highest, up to 10.33 mg·g-1; YS25 was second, increased by 8.17 mg·g-1;QZ1 was third which was 3.11 mg·g-1. 4. Effect of boron fertilizer on the content of N, P and K in sweet potato, existence difference between varieties, and the influence on the early stage of sweet potato was greater than that of the late growth sta ge. The content of potassium in stem and leaf of sweet potato increased after applying boron, but decreased in root. Besides, it also could increased the nitrogen content in YS25. However, the content of phosphorus in the sweet potato was decreased in YS25. Application boron made the nitrogen content in SS19 decreased, and the content of phosphorus in QZ1 decreased either. 5. In late growth stage, application boron inhibits photosynthesis of LS9, but could promote potato photosynthesis of YS25. 6. Lower boron concentration could reduce SOD activity and increase POD activity; CAT activity and nitrate reductase activity affected by different boron concentration is large, both low and high boron concentration could reduce the CAT and the nitrate reductase activity. The content of MDA was related to the boron sensitivity from sweet potato cultivars. When concentration of LS9 was 1.43 mg·L-1, the lowest the MDA content was, which would be high if abo ve or below this concentration; For SS19, when boron concentration was 2.86 mg·L-1, the MDA content would be lower. Low boron concentration could reduce root activity and increase chlorophyll content of sweet potato significantly. The soluble protein content was the highest in appropriate boron concentration. 7. Reaction of different sweet potato cultivars on boron concentration was distrinct. LS9 was sensitive, but XS23 and SS19 by contraries; 1.43 mg·L-1 boron was the most suitable concentration for LS9 and 2.86 mg·L-1 was appropriate for SS19 and XS23. |
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