Wang Yang, Lu Jianwei, Ren Tao, Hussain Saddam, Guo Chen, Wang Sen, Cong Rihuan, Li Xiaokun
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Microelement Research Centre, College of Resources and Environment, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan 430070, China.
Department of Agronomy, University of Agriculture, Jail Road, Faisalabad, Punjab 38040, Pakistan.
AoB Plants. 2017 Mar 30;9(2):plx012. doi: 10.1093/aobpla/plx012. eCollection 2017 Mar.
The increasing food demands from an expanding population necessitate global efforts to increase crop production and ensure food security. The rate of nitrogen (N) fertilizer application is strongly related to crop yield. However, although the application of N fertilizer significantly increases the number of tillers in rice, late emerging tillers usually produce lower yields compared with early emerging tillers. Understanding the physiological constraints of late emerging rice tillers is critical for further increasing rice grain yields. Two-year field experiments, consisting of four nitrogen fertilizer levels, were conducted in order to study variations in the physiological characteristics of different types of tillers. The results revealed that the contributions of late emerging tillers to population rice grain yields improved with increased N levels. However, spikelets per panicle and the grain filling of late emerging tillers were significantly lower than that of the main stems or early emerging tillers under all N levels. The nitrogen harvest index of late emerging tillers was lower than that of main stems and early emerging tillers, and differences gradually increased under higher N rates. Nutrient source deficiency was a primary factor for the low productivity of late emerging tillers. Additionally, rapid malondialdehyde accumulation and delayed emergence determined the short growth duration of late emerging tillers. Further, low actual photochemistry efficacy (Φ) resulted in insufficient photosynthetic assimilate supply in late emerging tillers, whereas highly constitutive non-photochemical energy dissipation (Φ) might damage the photosynthetic system. Moreover, the low activity of SuSase and spikelets per panicle revealed both inadequate sink activities and storage sites. The identification of these limiting factors in late emerging rice tillers will assist in closing the 'yield gap' between late emerging tillers and early emerging tillers, and contribute to further increasing rice grain yields.
不断增长的人口对粮食需求的增加，使得全球有必要努力提高作物产量并确保粮食安全。氮肥施用量与作物产量密切相关。然而，尽管施用氮肥显著增加了水稻的分蘖数，但与早期分蘖相比，晚期分蘖通常产量较低。了解晚期水稻分蘖的生理限制因素对于进一步提高水稻产量至关重要。为了研究不同类型分蘖的生理特征变化，进行了为期两年的田间试验，试验设置了四个氮肥水平。结果表明，随着氮肥水平的提高，晚期分蘖对水稻群体产量的贡献有所增加。然而，在所有氮肥水平下，晚期分蘖的每穗颖花数和籽粒充实度均显著低于主茎或早期分蘖。晚期分蘖的氮收获指数低于主茎和早期分蘖，且在较高氮肥施用量下差异逐渐增大。养分源缺乏是晚期分蘖生产力低下的主要因素。此外，丙二醛的快速积累和出蘖延迟决定了晚期分蘖的生长持续时间较短。此外，实际光化学效率（Φ）较低导致晚期分蘖光合同化物供应不足，而较高的组成型非光化学能量耗散（Φ）可能会损害光合系统。此外，蔗糖合成酶活性低和每穗颖花数少表明库活性和储存位点均不足。识别晚期水稻分蘖中的这些限制因素将有助于缩小晚期分蘖与早期分蘖之间的“产量差距”，并有助于进一步提高水稻产量。
