Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms
Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms
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DOI：
10.1111/pce.14042
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发表时间：
2021-03-18
影响因子：
7.3
通讯作者：
Watkins, James E., Jr.
中科院分区：
文献类型：
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作者：
Campany, Courtney E.;Pittermann, Jarmila;Watkins, James E., Jr.
植物多样性使蕨类植物辐射到被子植物为主的景观中的附生生态位。然而，我们的理解如何生态生理功能允许建立在树冠和潜在的过渡作用的半附生生活形式仍然不清楚。在这里，我们调查了39种蕨类植物在哥斯达黎加的热带森林，探讨附生性状分歧的系统发育背景。我们研究了陆生，半附生和附生蕨类植物的叶片水分亏缺的反应，并将这些发现与调节叶片水分状况的功能性状相关。与陆生蕨类植物相比，附生蕨类植物的木质部面积减少（-63%），柄长度缩短（-56%），叶片增厚（+41%），气孔密度降低（-46%）。与陆生蕨类植物相比，附生蕨类植物具有相似的膨压损失点，饱和时较高的渗透势和较低的组织电容。总的来说，半附生蕨类植物表现出的特点，共享陆生和附生物种的特征。我们的研究结果清楚地表明，在附生和半附生蕨类植物的水保守主义的流行，通过选择解剖和结构特征，避免叶水分胁迫。即使有可能进化限制的生理功能，适应干旱回避允许附生蕨类植物成功地忍受树冠栖息地的压力。
Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.