Lanthanum (La) improves growth, yield formation and 2-acetyl-1-pyrroline biosynthesis in aromatic rice (Oryza sativa L.)

BACKGROUND: Lanthanum (La) is a rare earth element that can influence plant growth and development. However, the effect of La on growth, yield formation and 2-acetyl-1-pyrroline (2-AP, a key compound responsible for the aroma of rice) biosynthesis in aromatic rice (Oryza sativa L. subsp. japonica Kato) has not been reported. Therefore, the present study investigated the effects of La on growth, photosynthesis, yield formation and 2-AP biosynthesis in aromatic rice through three experiments. RESULTS: Two pot experiments and a two-year field trial were conducted with different rates of La application (20–120 LaCl(3) mg kg(−1) and 12 kg ha(−1) LaCl(3)), and treatments without La application were used as controls. The results showed that the application of LaCl(3) at 80 and 100 mg kg(−1) and at 12 kg ha(−1) greatly increased the 2-AP content (by 6.45–43.03%) in aromatic rice seedlings and mature grains compared with the control. The La treatments also increased the chlorophyll content, net photosynthetic rate and total aboveground biomass of rice seedlings. Higher antioxidant enzyme (superoxide, peroxidase, and catalase) activity was detected in the La treatments than in the control. The La treatments also increased the grain yield, grain number per panicle and seed-setting rate of aromatic rice relative to the control. Moreover, the grain proline and γ-aminobutyric acid contents and the activity of betaine aldehyde dehydrogenase significantly decreased under the La treatment. The application of La to soil enhanced the activity of proline dehydrogenase by 20.62–56.95%. CONCLUSIONS: La improved the growth, yield formation and 2-AP content of aromatic rice and enhanced 2-AP biosynthesis by increasing the conversion of proline to 2-AP and decreasing the conversion of GABald to GABA.