Jiang Guo-Feng, Qin Bo-Tao, Pang Yu-Kun, Qin Lan-Li, Pereira Luciano, Roddy Adam B
Guangxi Key Laboratory of Forest Ecology and Conservation, Guangxi Colleges and Universities Key Laboratory for Cultivation and Utilization of Subtropical Forest Plantation, and State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry, Guangxi University, Daxuedonglu 100, Nanning, Guangxi, 530004, China.
College of Chemistry and Bioengineering, Hechi University, Yizhou, Guangxi, 546300, China.
New Phytol. 2024 Aug;243(4):1329-1346. doi: 10.1111/nph.19914. Epub 2024 Jun 19.
Drought-induced xylem embolism is a primary cause of plant mortality. Although c. 70% of cycads are threatened by extinction and extant cycads diversified during a period of increasing aridification, the vulnerability of cycads to embolism spread has been overlooked. We quantified the vulnerability to drought-induced embolism, pressure-volume curves, in situ water potentials, and a suite of xylem anatomical traits of leaf pinnae and rachises for 20 cycad species. We tested whether anatomical traits were linked to hydraulic safety in cycads. Compared with other major vascular plant clades, cycads exhibited similar embolism resistance to angiosperms and pteridophytes but were more vulnerable to embolism than noncycad gymnosperms. All 20 cycads had both tracheids and vessels, the proportions of which were unrelated to embolism resistance. Only vessel pit membrane fraction was positively correlated to embolism resistance, contrary to angiosperms. Water potential at turgor loss was significantly correlated to embolism resistance among cycads. Our results show that cycads exhibit low resistance to xylem embolism and that xylem anatomical traits - particularly vessels - may influence embolism resistance together with tracheids. This study highlights the importance of understanding the mechanisms of drought resistance in evolutionarily unique and threatened lineages like the cycads.
干旱诱导的木质部栓塞是植物死亡的主要原因。尽管约70%的苏铁科植物受到灭绝威胁，且现存苏铁科植物在干旱化加剧的时期实现了多样化，但苏铁科植物对栓塞扩散的脆弱性一直被忽视。我们对20种苏铁科植物叶片羽片和叶轴的干旱诱导栓塞脆弱性、压力-容积曲线、原位水势以及一系列木质部解剖特征进行了量化。我们测试了解剖特征是否与苏铁科植物的水力安全性相关。与其他主要维管植物类群相比，苏铁科植物对栓塞的抗性与被子植物和蕨类植物相似，但比非苏铁科裸子植物更容易受到栓塞影响。所有20种苏铁科植物都有管胞和导管，其比例与栓塞抗性无关。与被子植物相反，只有导管纹孔膜分数与栓塞抗性呈正相关。苏铁科植物中，膨压丧失时的水势与栓塞抗性显著相关。我们的研究结果表明，苏铁科植物对木质部栓塞的抗性较低，木质部解剖特征——尤其是导管——可能与管胞一起影响栓塞抗性。这项研究强调了了解像苏铁科植物这样在进化上独特且受到威胁的谱系中抗旱机制的重要性。
