角质层而非气孔调控木兰科植物叶片最小导度

Cuticle, but not Stomata, Regulates Minimum Leaf Conductance in Magnoliaceae

摘要:

为了解森林植物对干旱的响应与适应机制，对同质园中26种木兰科(Magnoliaceae)植物(16种常绿、10种落叶)的叶片最小导度(g_min)进行测定。结果表明，常绿物种的g_min[6.5 mmol/(m²·s)]显著低于落叶物种[11.6 mmol/(m²·s)]，且g_min总体上与叶片角质层厚度呈显著负相关，但与气孔大小、密度和气孔指数无显著相关性。g_min随物种分布地的年均温(MAT)升高而降低，而与年均降水(MAP)无显著相关性。然而，在常绿物种中，g_min随分布地MAP的降低而显著下降，表明降低g_min是常绿物种(而非落叶物种)采取的干旱适应策略。此外，常绿物种具有更厚的角质层，这解释了g_min较低的原因。木兰科物种的g_min存在显著的种间变异性，并主要受角质层特征而非气孔特征的调控。这为揭示植物干旱适应机制提供了新的视角。

Abstract:

To understand the response and adaptation mechanisms of forest plants to drought, the minimum leaf conductance (g_min) of 26 Magnoliaceae species (16 evergreen and 10 deciduous) in a common garden was measured. The results showed that the g_min of evergreen species [6.5 mmol/(m²·s)] was significantly lower than that of deciduous species [11.6 mmol/(m²·s)], and g_min was generally significantly negatively correlated with leaf cuticle thickness, but not significantly correlated with stomatal size, density, and stomatal index. The g_min decreased with the increase of mean annual temperature (MAT) of the species distribution area, but was not significantly correlated with mean annual precipitation (MAP). However, in evergreen species, the g_min decreased significantly with the decrease of MAP in distribution area, indicating that reducing g_min was an adaptation strategy to drought adopted by evergreen species (but not deciduous species). In addition, evergreen species had thicker cuticles, which explained the lower g_min. There was significant interspecific variability in g_minof Magnoliaceae species, and it was mainly regulated by cuticle characteristics rather than stomatal characteristics. These would provide a new perspective for revealing the drought adaptation mechanisms of plants.