田菁以磷增氮的研究

对环境施磷增加田菁[Sesbania cannabina(Retz.)pers.]结瘤固氮的作用是有限度的,受环境供磷水平的制约。 在广州石牌地区花岗岩发育赤红壤中,田菁以磷增氮的土壤有效磷临界水平(ppm P)为25.6(0.1 N HCL法)。 在无氮培养液中,秋植和春植田菁以磷增氮的供磷临界水平(毫摩尔P)分别为0.78和0.48,植株体内含磷量的临界水平(P％)分别为0.213和0.157。该临界供磷水平与含磷量有受季节性影响的倾向。介质的高磷水平还会引起田菁固氮量的下降。 在低磷的介质中,增磷对田菁根瘤的形成,发育和固氮酶活性有明显的促进作用。在磷供应达到一定水平后,继续增磷的促进作用不显著。未发现高磷供应对田菁的根瘤数有不良影响,但对其根瘤干重、特别是固氮酶活性有抑制作用。

A STUDY ON THE PHOSPHORUS APPLICATION ENHANCING NITROGEN FIXATION ABILITY OF LEGUMES (PAENFAL) EFFECT OF Sesbania Cannabina (Retz.) Pers.

Phosphate application in environment enhancing nodulation and nitrogen fixation of leguminous plant Sebania Cannabina (Retz.) pers. was not unlimited. It was inhibited by the available-P level in the environment.Related with the 'PAENFAL' effect of Sesbania Cannabina (Retz. ) Pers. , the critical available-p value (O.1 N HCL method) of lateritic red soil in plowed layer in the granitic area of Guangzhou was 25.6 ppm P. Also in nitrogen-free nutritional solution, ( 1 ) the critical phhosphorus concentration (mM P) were 0.78 and 0.48, and (2) the critical phosphorus content of plant (P%) were 0.213 and 0.157 separately in Autumn and Spring. These two critical values trended to be influenced by the seasonal chanbe The. significant decrease of fixed nitrongen by this plant was observed in the excessive-P solution. Significant promotion effect of increasing phosphorus supply on the nodulation, total dry weight of nodules and nitrogenase activity were obtained in low-P solution. This promotion effect was then leveled within a range of phosphorus supply. No harmful effect on nodulation was observed in the excessive-P supply but which inhibiting effect was appeared, not only on the total dry weight of nodules, but also on the nodule nitrogenase activity more seriously.