Studies on the Effect of the Relative Humidity of the Atmosphere on the Growth and Physiology of Rice Plants

Summary

The seedlings of rice (Oryza sativa cv. Nipponbare) at a plant age of 3 leaves, were cultured for 10 days in a 12-h light/12-h dark cycle, and exposed to 60% (low) or 90% (high) relative humidity during the light and dark period in all combinations. Low humidity in light and high humidity in darkness, significantly increased the rate of leaf emergence, plant height, leaf area, leaf blade length, the number of roots, total root length and dry matter production as compared with low humidity in both light and dark periods. These results suggested that the effects of high humidity during the dark period on the growth and dry matter production is not nullified by low humidity during the light period. High humidity during the light period was significantly more effective than that during the dark period for the growth expressed by these parameters. The effects of high humidity during the light and dark periods on the plant height, leaf sheath length and width of leaf blade were additive, but those on the leaf-emergence rate, number of roots, total root length, leaf area, leaf blade length and dry matter production were not additive.

Key words:

• Dry matter production
• Growth
• Photosynthesis
• Relative humidity
• Rice