Hydroponics Silicon Maize Seedlings Low Phosphorus Stress Relief Role

To discuss the alleviation of silicon on low-phosphorus stress of maize, the capability of low phosphorus tolerance about 9 maize inbred lines and 7 hybrids was firstly screened and identified by hydroponic culture. Then, one screened inbred lines and one hybrid was selected separately, both of which were the typical strong sensitivity to low-phosphorus stress and the high tolerability to low-phosphorus stress. Different Si concentration were added to the solution with low-phosphorus in order to investigate the characteristics of silicon and phosphorus uptake and accumulation, the photosynthetic characteristics and the physiological characteristics of dry matter accumulation in maize seedlings. Thus, the alleviation of silicon on low-phosphorus stress of maize seedlings was discussed, and the results were as follows:1. The effect of low phosphorus stress on physiological characteristic of maize seedlings, dry matter accumulation, P-accumulation and P-utilization efficiency was significantly. For example, the plant became short, P-accumulation decreased, chlorophyll content reduced, net photosynthetic rate declined and dry matter accumulation descend, especially the aerial part. However, the effect of low phosphorus stress on different varieties (inbred lines) varied a lot, which indicated that the capability of low phosphorus tolerance had an obvious genotype effect. Generally, the P-accumulation capability of inbred lines was better, while the P-utilization efficiency of hybrid was higher.2. According to the physiological characteristics of maize seedlings with low-phosphorus stress, the calculating method of composite tolerant low-phosphorus index was put forward in this thesis. The index could integrate much evaluating indicator information, overcome the disunity of dimension (unit) in different indexes and the difference of order of magnitude to reflect comprehensively the capability of composite tolerant low-phosphorus in different varieties (materials). Accordingly, maize inbred lines and hybrid with the strong sensitivity to low-phosphorus stress and the high tolerability to low-phosphorus stress were screened and identified.3. Appropriate Si concentration application to the low phosphorous nutrient solution could alleviate the low phosphorous stress, enhance the growth of maize seedlings and increase dry matter accumulation. And the accrued extent of the strong sensitivity to low-phosphorus stress variety (material) was larger than that of the high tolerability to low-phosphorus stress variety. However, the dry matter accumulation reached the most when Si concentration was 1.5 mmol/L in the low P nutrient solution, whatever the strong sensitivity to low-phosphorus stress variety (material) or the high tolerability to low-phosphorus stress variety (material).4. Si application to the low phosphorous nutrient solution had a significant effect on the chlorophyll content and the net photosynthetic rate of maize leaf. Appropriate Si concentration application could increase the chlorophyll a, chlorophyll b and total chlorophyll content, so the net photosynthetic rate of maize leaf was also raised. The photosynthetic rate of two maize varieties with strong sensitivity to low-phosphorus stress K335 and Chuandan19 reached the highest when Si concentration was 1.5 mmol/L in the low P nutrient solution; while the appropriate Si concentration of the maize varieties with high tolerability to low-phosphorus stress was relatively lower, and the photosynthetic rate arrived at the highest when Si concentration was 0.5-1.5 mmol/L in the low P nutrient solution. Therefore, Si could increase chlorophyll content and photosynthetic rate of maize leaf, which was the material foundation of alleviation of silicon on low-P stress.5. Silicate application under low-P stress could enhance not only Si adsorption and its content and accumulation in different organs of maize seedlings, but also P absorption and its content and accumulation in different organs of maize seedlings. The relationship between P accumulation and Si content as well as its accumulation was quadratic function, which implied that Si could promote obviously P absorption under the condition of low Si concentration, but excessive Si concentration would inhibit P absorption. Thus, appropriate Si concentration would enhance P absorption and accumulation, which was the nutritious physiology basis of alleviation of silicon on low-P stress.