Chen Guopeng, Liang Bing, Bawa George, Chen Hong, Shi Kai, Hu Yun, Chen Ping, Fan Yuanfang, Pu Tian, Sun Xin, Yong Taiwen, Liu Weiguo, Liu Jiang, Du Junbo, Yang Feng, Wang Xiaochun, Yang Wenyu
College of Agronomy, Sichuan Agricultural University, Chengdu, China.
Sichuan Engineering Research Center for Crop Strip Intercropping System, Key Laboratory of Crop Ecophysiology and Farming System in Southwest China, Ministry of Agriculture, Chengdu, China.
Front Plant Sci. 2021 Sep 6;12:724909. doi: 10.3389/fpls.2021.724909. eCollection 2021.
Water, nutrient, light, and interspecific facilitation regulation of soil physicochemical properties and root morphology modulate nitrogen (N) uptake in cereal and legume intercropping systems. However, maize root morphological plasticity and N uptake capability response to gravity in the intercropping system remains to be determined. In this study, maize was grown under 20 cm (I), 40 cm (I), and 60 cm (I) of narrow row spacing in an intercropping system (maize-soybean strip relay intercropping) and equal row spacing of monoculture (M) in a 2-year field experiment. As a supplementary for the field experiment, maize root barrier and plant inclination experiments were conducted. Plant inclination, brace root morphology, N uptake, indole-3-acetic acid (IAA) level, IAA synthesis genes, and grain yield were assessed. The result showed that the plant inclination increased with decreasing narrow row spacing in intercropping system. Also, the brace unilateral root growth ratio (BURR) increased with increasing plant inclination in intercropping treatments. The plant inclination experiment showed the BURR achieved 94% after inclination at 45°. BURR tended to be positively correlated ( = 0.00) with plant inclination. Thus, gravity (plant inclination) causes brace unilateral root growth. The IAA concentration of stem nodes in the wide row increased with increasing plant inclination, while the IAA accumulation decreased in the narrow row. The and genes (associated with IAA biosynthesis) were highly expressed in a wide row. There was a strong correlation ( = 0.03) between the IAA concentration of wide row and the BURR. Therefore, gravity regulates the IAA level, which affects BURR. In addition, the brace root number, volume, and surface area were decreased when BURR was increased. Subsequently, the leaf N, cob N, and kernel N accumulation were reduced. These organs N and grain yield in I were not significantly different as compared to the control treatment. The excessive brace unilateral root growth was not conducive to N uptake and increased yield. Our results suggest that gravity is essential in regulating root morphology plasticity by regulating IAA levels and decreasing N uptake capacity. Furthermore, these results indicate that plant inclination can regulate root phenotype and N uptake of maize and by adjusting the spacing of narrow maize row, we can improve the N uptake and yield of the maize-soybean strip relay-intercropping system.
水分、养分、光照以及种间促进作用对土壤理化性质和根系形态的调节，会影响谷类与豆类间作系统中的氮素吸收。然而，间作系统中玉米根系形态可塑性及氮素吸收能力对重力的响应仍有待确定。本研究中，在两年的田间试验里，玉米在间作系统（玉米 - 大豆条带交替间作）中分别种植于20厘米（I）、40厘米（I）和60厘米（I）的窄行距下，以及在单作（M）的等行距条件下。作为田间试验的补充，还进行了玉米根系屏障和植株倾斜试验。对植株倾斜度、支持根形态、氮素吸收、吲哚 - 3 - 乙酸（IAA）水平、IAA合成基因及籽粒产量进行了评估。结果表明，间作系统中，植株倾斜度随窄行距减小而增加。此外，间作处理中，支持根单侧根生长比率（BURR）随植株倾斜度增加而增大。植株倾斜试验表明，倾斜45°后BURR达到94%。BURR与植株倾斜度呈正相关（ = 0.00）。因此，重力（植株倾斜度）导致支持根单侧根生长。宽行中茎节的IAA浓度随植株倾斜度增加而升高，而窄行中IAA积累量下降。与IAA生物合成相关的 和 基因在宽行中高表达。宽行IAA浓度与BURR之间存在强相关性（ = 0.03）。所以，重力调节IAA水平，进而影响BURR。此外，BURR增加时，支持根数量、体积和表面积减少。随后，叶片氮、穗轴氮和籽粒氮积累量降低。与对照处理相比，I处理中这些器官的氮含量和籽粒产量无显著差异。支持根单侧根过度生长不利于氮素吸收和增产。我们的结果表明，重力通过调节IAA水平和降低氮素吸收能力，在调节根系形态可塑性方面至关重要。此外，这些结果表明，植株倾斜度可调节玉米根系表型和氮素吸收，通过调整玉米窄行间距，可提高玉米 - 大豆条带交替间作系统的氮素吸收和产量。
