Growth Promotion of Rice ( Oryza sativa L.) Seedlings by Application of L-β-phenyllactic Acid

摘要

Fine branching of lateral roots and the framework of seminal or nodal roots play an important role in performing function of a root system. The effects of L-β-phenyl lactic acid (LPA) on growth of rice ( Oryza sativa L.) seedlings have not been fully elucidated. Therefore, growth promotive effects of LPA on roots and shoots in rice seedlings were investigated. Rice seedlings were cultured in seed packs^TM containing 1/100-strength Murashige and Skoog (MS) medium with or without 100 mg L^-1 LPA at 30°C for 14 days. The total root length and total root surface area were calculated by digital image analysis. LPA-treated seedlings showed a 24% increase in plant height and a 26% increase in seminal root length compared with those of the control. The dry weight of shoots was markedly increased and that of roots was slightly increased by LPA. LPA treatment had no effect on the number of seminal and nodal roots per seedling. Digital image analysis revealed that LPA significantly increased the total length and surface area of fine roots (less than 0.757 mm in diameter). In addition, LPA did not affect the distribution of total length or surface area of rice roots in any diameter classes compared with that of control. The findings suggest that the growth-promoting effects of LPA on rice shoots can be attributed to increased water and nutrient absorption and/or the seed endosperm utilization efficiency, as a result of increased total length and surface area of roots.