Abstract: In order to study the impacts of planting density of potted rice seedlings by mechanical transplanting method on plant form and micrometeorology, a field experiment was conducted using conventional japonica rice (Nanjing 44, Wuyunjing 24), japonica hybrid rice (Yongyou 8, Changyou 5), and indica hybrid rice (Liangyoupeijiu, II You 084), which have been widely grown in the southern China, with high, medium and low density treatments of different hole spacing in potted seedling mechanicaltransplanting (12, 14, and 16 cm), and the conventional blanket seedling mechanicaltransplanting as control. The results showed that the distances of leaf occiput between flag leaf and top 2nd leaf and between top 3rd leaf and top 4th leaf, effective leaf area ratio, highly effective leaf area ratio, angle of flag leaf, lengths of top 2nd and 3rd upper leaves, leaf angle, lengths of panicle and uppermost two internodes increased with reducing the planting density, while canopy temperature and humidity decreased with reducing the planting density. Conventional japonica rice with the low density and japonica hybrid rice with the medium density had higher canopy light intensities, while indica hybrid rice presented an opposite trend. Compared with the control, rice plants with potted seedlings by mechanical transplanting exhibited a uniform plant form, and canopy temperature and humidity decreased. Combined with the variation characteristics of plant form, conventional japonica rice planting with 12 cm hole spacing could make better use of the resources of temperature and light, japonica hybrid rice planting with the hole spacing of 14 cm could effectively improve the light and ventilation conditions, coordinate grain contradiction, and hybrid indica rice planting with 16 cm hole spacing was not only suitable for mechanical cultivation, but also improved the percentage of spikeforming tillers.

Key words: salicylic acid, proliferation, Ulva prolifera, chlorophyll fluorescence, antioxidant