杨树无性系根系吸收H_2PO_4^-动力学特征与磷营养效率

PHOSPHATE UPTAKE CHARACTERISTICS OF KINETICS AND PHOSPHORUS EFFICIENCY IN CLONES OF POPLAR

在温室条件下 ,应用整株植物长期吸收的营养液培养方法研究杨树无性系根系吸收H2 PO4- 动力学特性及其与磷营养效率的关系 ,以揭示杨树不同无性系间磷营养效率差异的机理。结果表明 ,高效型无性系S1 7、S1 9和 1 0 5根系对H2 PO4- 离子的吸收能力明显强于低效型无性系 1 0 6、797、Ⅰ -69、1 3 88和 3 2 44。与低效型无性系相比 ,S1 7、S1 9和 1 0 5具有较小的米氏常数Km 和吸收临界浓度Cmin,说明它们的根系对H2 PO4- 的亲合力、对低磷浓度的耐受能力较强。在缺磷胁迫条件下 ,S1 7、S1 9和 1 0 5根系系统对H2 PO4- 的亲合能力可增加 2 0 %以上 ,其Km 值分别从 1 3 8、1 3 4和 1 4 0 μmol·L- 1 下降到 1 0 1、1 0 7和 1 1 2 μmol·L- 1 ,而低效型无性系的亲合力则变化很小 ,增加不足 5 %。同样 ,高效型无性系对低磷的耐受能力可增加 85 %以上 ,其Cmin 分别从2 5 5、2 94和 2 68μmol·L- 1 下降到 0 3 0、0 3 5和 0 40 μmol·L- 1 ,但低效型无性系的增加均不足 1 5 %。杨树无性系在根系吸收H2 PO4- 动力学特性方面的不同是其磷营养效率差异的重要原因之一。最大吸收速率Vmax,作为根系吸收动力学参数之一 ,对阐明杨树无性系磷营养效率的作用尚不够确定。

In order to explore the mechanism of interclonal differences of poplar in P efficiency and to find out a new way in breeding improved variety of poplar, phosphate uptake characteristics of kinetics and the relation between the kinetic characteristics and P efficiency were conducted by the method of solution culture with long term absorption by intact plants for poplar seedling in greenhouse. The results showed that the root uptakes of phosphate were obviously stronger in clone S 17, S 19, and 105, which were attested as high P efficiency, than in clone 106, 797, I-69, 1388, and 3244, which were low P efficiency clones. The values of K m, the Michaelis constant, which is the concentration where influx is half of V max, and C min, the critical concentration, the ion concentration in solution below which net influx of the ion ceases, of S 17, S 19, and 105 were much smaller than those of other five clones, respectively. This indicated that clones of high P efficiency were much stronger than those of low P efficiency in the affinity of root system to phosphate and in tolerating P deficiency. As a result of P deficiency stress such affinities were increased over 20% for the clones of high P efficiency but below 5% for the clones of low P efficiency, as indicated by the values of K m under two P treatments. Similarly, as showed by the values of C min, the tolerance to P deficiency stress was raised more than 85% for the clones of high P efficiency but less than 15% for the clones of low P efficiency. Consequently, variation in P uptake characteristic parameters of kinetics by root systems of various poplar clones was one of important mechanisms for the interclonal difference in P efficiency, and will probably be of great significance in breeding improved poplar variety in the future. Further more studies were needed to explain the difference of phosphorus efficiency by the index of V max.