Phosphorus deficiency in host plant enhances production of germination stimulants for root parasite Orohanche minor Sm

摘要

Orobanche species, root parasitic weeds, causing enormous damage to agriculture prevail on nutrient deficient soils. It is known that their emergence is often suppressed by the application of fertilizers. However, it, has not been clarified yet whether nutrients affect the production and/or excretion of germination stimulants or that of germination inhibitors. In this study, the amounts of orobanchol, one of germination stimulants for O. minor, excreted into water culture solution by its host red clover (Trifolium pratense L.) plants grown under various low nutrient levels (N, P, K, Ca, and Mg) were quantified by using LC/MS/MS. Germination stimulant activities of the root exudates of the, plants grown under each low nutrient level were also assessed by bioassays. The results clearly demonstrated that phosphorus deficiency enhanced both the production and/or excretion of orobanchol and germination stimulant activities. Therefore, the application of phosphate to soils is expected to reduce infestation of root parasitic weeds by retarding excretion of germination stimulants from host plants.