西南弱光地区机插杂交籼稻“减穴稳苗”栽培的群体冠层质量特征

【目的】探明机插条件下减穴稳苗配置对杂交籼稻群体冠层质量的影响,为西南弱光稻区杂交籼稻机插栽培技术的推广应用提供理论支撑。【方法】2016—2017年采用两因素随机区组田间试验,因素1,2年均为不同田间配置,设常规配置（30 cm×12 cm）和减穴稳苗（30 cm×23 cm）;因素2,2016年为不同株型水稻品种（F优498,中后期株叶型松散;宜香优2115,中后期株叶型上紧下披）,2017年为不同基本苗（42×10⁴/hm²和63×10⁴/hm²）;研究了不同田间配置对机插杂交籼稻群体冠层结构、光合特性和微环境（冠层温度、湿度和透光率）的影响。【结果】（1）减穴稳苗齐穗期能维持与常规配置相当的单茎绿叶面积、粒叶比和上三叶比叶重,其中2017年倒二叶与倒三叶比叶重显著增大;齐穗期剑叶光合速率、气孔导度、蒸腾速率分别较常规配置显著提高23.84%、23.53%和13.79%。（2）较常规配置,减穴稳苗显著增大各时期冠层幅度,提高冠层透光率,降低收敛指数,群体通透性更好;减穴稳苗处理提高了2016年F优498孕穗期和齐穗期的一次分蘖角度,而宜香优2115的一次分蘖角度2年均表现为减穴稳苗小于常规配置。（3）相关分析表明,孕穗期冠层日均温、昼夜温差和昼夜湿差与齐穗期剑叶和倒二叶比叶重呈显著或极显著正相关,与齐穗期收敛指数呈显著负相关;此外,孕穗期冠层日均温和昼夜湿差还与齐穗期冠层幅度呈显著正相关;齐穗期冠层日均温和昼夜温差与分蘖盛期、拔节期及齐穗后20 d的一次分蘖角度呈显著或极显著负相关,日均相对湿度则相反。减穴稳苗有效地改善了植株冠层结构,从而显著提高孕穗期和齐穗期的冠层温度和昼夜温差,提高孕穗期、齐穗期和齐穗后20 d的昼夜湿差,并显著降低日均相对湿度。【结论】减穴稳苗田间配置优化了机插杂交稻的群体冠层结构和光分布,增大了群体内部昼夜温差和湿差,降低了相对湿度,提高了群体质量和光合速率,为高产稳产奠定了基础,是西南弱光稻区进一步推进机插秧发展的重要技术途径。

Canopy Population Quality Characteristics of Mechanical Transplanting Hybrid Indica Rice with “Reducing Hills and Stabilizing Basic-Seedlings” in Low-Light Region of Southwest China

【Objective】The effects of reducing hills and stabilizing basic-seedlings (RHSB) on population canopy quality characteristics of mechanical transplanting indica hybrid rice were investigated in this study, which could provide theoretical support for the promotion and application of mechanical transplanting technology of hybrid rice in low-light paddy region of Southwest China. 【Method】 A two-factor random block design experiment with different rice varieties (Fyou 498 is a loose plant type, and Yixiangyou 2115 is a compact upper and drooping lower plant type at middle and late stages) and different basic seedlings rate (42×10⁴/hm² and 63×10⁴/hm²) was conducted to study the effects of different field collocation patterns (conventional field collocation (CFC) and RHSB) on the canopy architecture, photosynthetic characteristics, and microclimate environment (e.g. canopy temperature, humidity, and light transmittances) of mechanical transplanting hybrid rice population in 2016 and 2017. 【Result】(1) Compared with CFC, RHSB with a greater specific leaf weight of the upper three leaves (F_{second leaf}=23.67^** and F_{third leaf}= 16.91^** in 2017) could maintain a similar green leaf area per stem and grain/leaf ratio at heading stage. Compared with CFC, RHSB also led to the 23.84%, 23.53%, and 13.79% significant increase in photosynthetic rate, stomatal conductance, and transpiration rate of flag leaf at heading stage, respectively. (2) RHSB markedly decreased the canopy convergent index, but increased the canopy amplitude, which increased in light transmittance and ventilation of canopy. RHSB increased the angle of primary tillerings of Fyou 498 at booting stage and heading stage in 2016, but decreased the angle of primary tillerings of Yixiangyou 2115 in 2016 and 2017. (3) Correlation analysis indicated that daily average temperature and diurnal variations of temperature and humidity at booting stage were significantly or extremely significantly positively correlated with the specific leaf weight of the flag leaf and the 2nd leaf at heading stage, but significantly negatively correlated with plant convergent index at heading stage. Furthermore, the daily average temperature and diurnal variations of humidity at booting stage was significantly positively correlated with canopy amplitude at heading stage. Daily average temperature and diurnal variations of temperature at heading stage were significantly or extremely significantly negatively correlated with the angle of primary tillering at tilling stage, jointing stage, and 20 d after heading stage. However, the inverse relation was observed by daily average relative humidity. RHSB could optimize the canopy architecture of rice, which contributed to the increase in canopy temperature and diurnal the variations of temperature at booting and heading stages, and increase diurnal the variations of humidity at booting, heading and 20 d after heading stage, but decrease in the relative humidity.【Conclusion】As one of the main technology that improved the mechanization level of rice production in the low-light region of Southwest China, RHSB optimized the population canopy structure and light distribution of mechanical transplanting hybrid rice, which resulted in the increase in the temperature and humidity difference between day and night within the population, and reduced the relative humidity. This contributed to the improvement in the population quality and photosynthetic rate, and contributed to the increase in rice grain yield.