磷肥对紫花苜蓿再生过程中根茬组织非结构性碳水化合物利用的影响

Effects of phosphate fertilizer on utilization of non-structural carbohydrate in resident tissue of Medicago sativa during the early regrowth stage

田间试验研究了施磷肥对紫花苜蓿再生过程中主根、根冠和残茬中非结构性碳水化合物(NSC)贮存量变化的影响。结果表明,紫花苜蓿NSC主要贮存在主根和根冠部,主根和根冠中的淀粉是再生过程中被利用最多的NSC。施磷肥显著提高了刈割时主根和根冠部淀粉的贮存量,270 kg P2O5/hm2处理的植株主根和根冠部淀粉贮存量分别比0 kg P2O5/hm2处理的植株高73.5%和31.1%;施磷肥处理提高了主根中α-淀粉酶的活性,加快了主根和根冠部贮存淀粉在再生早期的降解,提高了主根和根冠部淀粉转化为再生生物量的效率,促进了休眠芽的萌发和新生茎的生长。270 kg P2O5/hm2处理的植株刈割后13 d的每株再生生物量极显著高于不施磷处理的植株(P<0.01)。结果说明,紫花苜蓿主根和根冠部贮存的NSC是再生的主要营养源;施磷肥通过提高紫花苜蓿根茬组织中NSC的贮存量和利用效率,为刈割后的早期再生提供充足的养分,从而加快紫花苜蓿的再生。

A field experiment was conducted to study the effects of phosphate fertilizer on utilization of nonstructural carbohydrate （NSC） stored in the main root, crown, and stubble of alfalfa （Medicago sativa） during early regrowth after defoliation. NSC is mainly stored in the root and crown. A great deal of starch, the major component of stored NSC, was utilized during early regrowth. With increasing rates of phosphate fertilizer,starch reserves increased in the main root and crown and at 270 kg P2O5/ha starch reserves were 73.5% and 31.1% higher respectively than those in the control. Phosphate fertilizer improved the activity of α-amylase and accelerated the hydrolyzis of starch in the main root and crown, thus promoting regrowth by enhancing mobilization of starch reserves for emergence of dormant buds and new shoots after defoliation. The dry weight of plants treated with 270 kg P2O5/ha was significantly （P〈0.01） greater than the control 13 days after defoliation. NSC in the main root and crown of alfalfa is the main source of nutrients during early regrowth and phosphate fertilizer improved the storage and conversion efficiency of NSC thus accelerated regrowth of alfalfa after defolition.