Abstract:

The physiological and biochemical changes during germination of immature brown rice under hypoxia stress were
investigated. The results indicated that the germination rate of immature brown rice was 79.3%, shoot length was 1.92 mm,
respiration rate was increased by 6.6 times, and density was 0.79 g/mL, after 48 h of germination under hypoxia stress.
During germination, water content was increased firstly and then tended to be stable. Starch content showed a continuous
decline, while the contents of reducing sugars and free amino acids were increased. These changes were consistent with
those in mature brown rice and showed no significant difference. In addition, accumulation of γ-aminobutyric acid (GABA)
was accelerated with increasing germination time. GABA content was increased by 108% at 48 h. Meanwhile, glutamate
decarboxylase (GAD) activity and Glu content showed no significant difference from those of the mature brown rice.
GABA content in immature brown rice germinating under hypoxia stress was correlated significantly positively with sprout
length, respiration rate, free amino acid content and GAD activity, but significantly negatively with Glu and starch contents.
Germination of immature brown rice under hypoxia stress can improve its nutritional quality and provide an excellent
GABA-enriched material.

Key words: immature brown rice, germination, hypoxia stress, physiology and biochemistry