Abstract: Water stress is a major limiting factor
for plant growth and development. In this study,
we investigated the effects of L-β-phenyllactic
acid (LPA) on growth of rice (Oryza sativa L.)
seedlings under polyethylene glycol (PEG)-
induced water deficit conditions. Seedlings were
culture at 30°C for 14 days in growth pouches
supplemented with 1/100-strength Murashige
and Skoog (MS) medium and PEG in the
presence or absence of 100 mg L-1 LPA. As
evidenced by plant height, LPA application
enhanced seedling growth under PEG-induced
water deficit by 13%. The shoot dry weight was
slightly increased, whereas that of roots was
markedly enhanced during LPA treatment by
26% under water-deficit conditions. No difference
was observed among treatments in the number
of roots per seedling. The ratio of shoot dry
weight to shoot length (RWL) was constant
regardless of treatment, indicating that LPA does
not cause spindly shoot growth. The total length,
surface area, and volume of fine roots were
increased by LPA under PEG-induced water
deficit conditions. Plant height was significantly
correlated with total root surface area and volume.
The results imply that PEG-induced water deficit
in rice seedlings can be alleviated by LPA
application. This alleviative effect is partially
attributable to alterations in root system
developmental patterns, with increases in fine
root total length, surface, and volume
accelerating water and nutrient acquisition from
the culture medium.