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研究大豆氮素营养过程和估价根瘤氮的作用,以及估算固氮量时,必须了解大豆根瘤固氮活性动态的规律。对于大豆根瘠固氮活性的季节动态,已为众多研究者所重视(Lawn1974,Klucas 1974;Harper 1974;Thibodeau 1975,Weil 1975;Skrolets 1978;Wych 1978,Sung 1981)。他们的研究认为,大豆植株早期固氮活性较低,随之明显增高,开花之后达到高峰,一旦进入鼓粒期就显著下降。他们并把这种陡坡式的下降,归结于发育中的籽粒与根瘤间对有效光合产物的竞争(Lawn 1974)。Mague(1672)曾报导田间大豆的乙炔还原率有明显的日变化,其活性高峰出现在下午5时。Sloger(1975)指出固氮活性的日变化和根瘤呼吸是相似的,并取决于日辐射,整个采样期间的平均比活性在下午2—4时最高。
Studying the process of nitrogen nutrition in soybean and evaluating the effect of nodule nitrogen, and estimating the amount of nitrogen fixation, we must understand the dynamic rule of soybean nodule nitrogen fixation activity. The seasonal dynamics of barren nitrogen fixation in soybean has been highlighted by many researchers (Lawn 1974, Klucas 1974; Harper 1974; Thibodeau 1975; Weil 1975; Skrolets 1978; Wych 1978, Sung 1981). Their research suggests that early nitrogen fixation activity of soybean plants is lower, then significantly higher, peaked after flowering, and dropped significantly once it entered the druse. They also attribute this steep decline to the competition for effective photosynthate between developing kernels and nodules (Lawn 1974). Mague (1672) reported a significant diurnal change in the rate of acetylene reduction in field soybeans, with peak activity occurring at 5 p.m. Sloger (1975) pointed out that the diurnal variation of nitrogen fixation activity is similar to that of root nodules and depends on the daily radiation, with the average specific activity during the entire sampling period being highest at 2-4 o’clock.