| Based on the previous research at home and abroad, using ‘Yuyan 10’ as the material, four phosphate fertilizer applying levels were designed in a field experiment and a pot experiment to clarify the effects of phosphorus on the growth of root and aboveground of flue-cured tobacco in Xuchang, Henan in 2013-2014. And the relationship between root and shoot growth of flue-cured tobacco was analyzed and illustrated from three aspects. There were the accumulation and distribution of dry matter, nitrogen, phosphorus and potassium in different organ, the expression level of high affinity phosphate trans-protein gene in different organ, and the relevance of root indexes and aboveground indexes of flue-cured tobacco. The main results were as follows.1. Compared with control treatment, root dry weight and root volume were increased and root activity, total root absorption area per plant, root active absorption area per plant were improved by applying phosphate fertilizer. At the earlier growth stage, the values of those root indexes increased with the rate of phosphorus application increased and T3 had some advantages in root growth, while there was on significant difference between T2 and T3. At the later growth stage, T1 had the higher root dry weight, root volume, and root activity in the field experiment, and was higher than the CK significantly. Contrasting with this, in the pot experiment T2 had highest root fresh weight, root volume and total root absorption area per plant, and was higher than other treatments significantly. The possible reason for the different results for two years might be the limited soil nutrient for tobacco growth in pot and phosphorus was more dependent on the supply of fertilizers. This difference also showed that the effects of phosphate fertilizer applying levels were greater than the proportion of nitrogen, phosphorus and potassium on root growth and physiological activity of flue-cured tobacco in the fertilization.2. Compared with control treatment, the plant height, stem circumference and lower leaf area increased by applying phosphate fertilizer, but there was no significant effect on the effective leaves number. At field growth vigor aspect, the plant of control treatment was slow-growing and its leaf was narrow and the plant height was significantly lower than other treatments. Chlorophyll contents in all treatments were as follows: before 45 days after transplanting, the content of chlorophyll a and chlorophyll b in middle leaf of T2 and T3 was significantly higher than that of CK. At the mature stage the chlorophyll content of T3 declined faster than the other treatments and was significantly lower than that of CK and T1. The net photosynthetic rate of T2 and T3 was significantly higher than that of CK before 60 days after transplanting, since no significant difference among treatments. The difference of chlorophyll content and net photosynthetic rate among four treatments meant that the chlorophyll content in tobacco leaves and leaf net photosynthetic rate were increased in the earlier growth stage and the chlorophyll was transformed and broke down timely in the later growth stage by increasing the amount of phosphate fertilizer in a certain range, which provided a guarantee for the maturity of tobacco leaf.3. With the advance of growth period, the accumulation amount of dry matter, nitrogen, phosphorus and potassium in tobacco leaf, root and stem was gradually increased, while the content was declined overall. The distribution proportions of nitrogen, phosphorus and potassium in leaf with the advance of growth period gradually declined, which gradually raised in stem and fluctuated in root. And the amount of phosphate fertilizer couldn’t change this trend, which only affected the value. As regarded the different organs, there were largest distribution proportion of dry matter, nitrogen, phosphorus and potassium and accumulation amount in leaf. The growth of root and stem provided strong support for tobacco leaf. Meanwhile, the correlation between the expression level of high affinity phosphate trans-protein gene in leaf and root and the content and accumulation of phosphorus was analyzed. The result showed that under phosphorus deficiency stress the coordination in root and leaf growth of flue-cured tobacco was broken. The relationship between root and leaf was more competitive as they competed for a limited number of nutrients for their growth. The growth of root system could be predicted by aboveground growth of flue-cured tobacco and appropriate measures could be take in a timely manner for the significantly and positively relation between root system indicators and aboveground morphology indicators.Based on the research results above, for the middle of Henan where the available phosphorus content of soil was 9.77-12.53 mg/kg, the recommended phosphorus fertilizer level and N and P2O5 ratio were 30-60 kg P2O5/hm2 and 1:1-2, respectively. The growth of root and shoot of flue-cured tobacco was mutual promotion and mutual coordination and gradually reached a state of equilibrium under suitable growth environment, and this balance had been broken, trying to reach a new balance when environmental conditions changed. Whereas, limited the self-regulation of root and shoot, just as CK and T3 in this experiment, the relation between the growth of root and shoot was more characterized as competition, eventually leading stunting or root growth redundancy. |
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