Stomatal conductance, xylem water transport, and root traits underpin improved performance under drought and well-watered conditions across a diverse panel of maize inbred lines
Stomatal conductance, xylem water transport, and root traits underpin improved performance under drought and well-watered conditions across a diverse panel of maize inbred lines
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DOI：
10.1016/j.fcr.2019.02.001
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发表时间：
2019-03-15
影响因子：
5.8
通讯作者：
Comas, Louise H.
中科院分区：
文献类型：
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作者：
Gleason, Sean M.;Cooper, Mitchell;Comas, Louise H.
我们评估了不同玉米自交系（美国玉米嵌套关联作图（NAM）群体的创始人）中与水获取和运输、气孔导度和光合作用相关的十六个性状，目的是确定哪些性状可以在缺水和水分充足的条件下改善生长。 Lasso 回归显示，三个关键性状解释了赤字灌溉下季末总生物量有意义且独立的变化比例（倍数 r(2) = 0.86）：1）最大净二氧化碳同化率（P = 0.007），2）一天中最热时段可实现的气孔导度（P = 0.005），3）根系的宽深比 苗期（P = 0.060），即最初的深根系发育有利于生长。在浇水良好的条件下，早晨的最大气孔导度（P = 0.014）和根系的宽深比（P = 0.043）被确定为有助于提高性能的关键性状（倍数r（2）= 0.68）。结构方程模型显示，缺水条件下的生长与中午发生的气孔导度（std coef = 0.75；P = 0.006）的相关性更强，而不是与最大气孔导度（std coef = 0.25；P = 0.368）的相关性更强。反过来，一天中气孔导度的维持取决于木质部组织的供水能力（每单位横截面积）（std coef = 0.48；P = 0.046）。与水分向气孔的运输和生长相一致，幼苗期的根系深度（r = 0.77；P = 0.003）和宽深比（r = 0.55；P = 0.064）也与木质部运输水分的能力相关，因此表明根、木质部和气孔性状之间的密切协调，以在水分亏缺和水分充足的条件下实现更大的生长。我们认为，在此考虑的干旱条件下，玉米的表现可能会通过降低气孔对水力和大气信号的敏感性、更大的木质部传导性以及更深但不一定更广泛的根系来改善。
We evaluated sixteen traits related to water acquisition and transport, stomatal conductance, and photosynthesis within a diverse panel of maize inbred lines, founders of the U.S. maize nested association mapping (NAM) population, with the aim to determine which traits confer improved growth under water deficit and well-watered conditions. Lasso regression revealed that three key traits explained meaningful and independent proportions of variation in total end-of-season biomass under deficit irrigation (multiple r(2) = 0.86): 1) the maximal net CO2 assimilation rate (P = 0.007), 2) the achievable stomatal conductance during the hottest part of the day (P = 0.005), and 3) the width-to-depth ratio of the root system at the seedling stage (P = 0.060), i.e., initial deep root system development facilitated growth. Under well-watered conditions, maximal stomatal conductance in the morning (P = 0.014) and the width-to-depth ratio of the root system (P = 0.043) were identified as key traits contributing to improved performance (multiple r(2) = 0.68). Structural equation models revealed that growth under water deficit was linked more strongly to stomatal conductance occurring during the middle of the day (std coef = 0.75; P = 0.006), rather than the maximal stomatal conductance (std coef = 0.25; P = 0.368). In turn, the maintenance of stomatal conductance through the middle of the day depended on the capacity of the xylem tissue to supply water (per unit cross-sectional area) (std coef = 0.48; P = 0.046). Aligned with the transport of water to the stomata and growth, root system depth (r = 0.77; P = 0.003) and width-to-depth ratio (r = 0.55; P = 0.064) at seedling stages were also correlated with the capacity of the xylem to transport water, thus suggesting close coordination between root, xylem, and stomatal traits to achieve greater growth under water deficit and well-watered conditions. We propose that maize performance under the drought conditions considered here, could likely be improved via lower stomatal sensitivity to hydraulic and atmospheric cues, greater xylem conductivity, and a deeper, but not necessarily more extensive, root system.