BIOGECO, INRA, University of Bordeaux, Cestas, France.
Naturalis Biodiversity Center, Leiden University, PO Box 9517, Leiden, the Netherlands.
Physiol Plant. 2018 May;163(1):59-72. doi: 10.1111/ppl.12654. Epub 2017 Dec 5.
Drought-induced xylem embolism is a key process closely related to plant mortality during extreme drought events. However, this process has been poorly investigated in crop species to date, despite the observed decline of crop productivity under extreme drought conditions. Interspecific variation in hydraulic traits has frequently been reported, but less is known about intraspecific variation in crops. We assessed the intraspecific variability of embolism resistance in four sunflower (Helianthus annuus L.) accessions grown in well-watered conditions. Vulnerability to embolism was determined by the in situ flow-centrifuge method (cavitron), and possible trade-offs between xylem safety, xylem efficiency and growth were assessed. The relationship between stem anatomy and hydraulic traits was also investigated. Mean P was -3 MPa, but significant variation was observed between accessions, with values ranging between -2.67 and -3.22 MPa. Embolism resistance was negatively related to growth and positively related to xylem-specific hydraulic conductivity. There is, therefore, a trade-off between hydraulic safety and growth but not between hydraulic safety and efficiency. Finally, we found that a few anatomical traits, such as vessel density and the area of the vessel lumen relative to that of the secondary xylem, were related to embolism resistance, whereas stem tissue lignification was not. Further investigations are now required to investigate the link between the observed variability of embolism resistance and yield, to facilitate the identification of breeding strategies to improve yields in an increasingly arid world.
干旱诱导的木质部栓塞是一个关键过程，与极端干旱事件中植物死亡率密切相关。然而，迄今为止，这一过程在作物物种中的研究甚少，尽管在极端干旱条件下观察到作物生产力下降。种间水力性状的变异经常被报道，但对作物种内变异的了解较少。我们评估了四个向日葵（Helianthus annuus L.）品种在充分供水条件下的栓塞抗性的种内变异性。栓塞易感性通过原位流离心法（cavitron）确定，并评估木质部安全性、木质部效率和生长之间可能的权衡。还研究了茎解剖结构与水力性状之间的关系。平均 P 为-3 MPa，但在品种之间观察到显著的变异性，范围在-2.67 和-3.22 MPa 之间。栓塞抗性与生长呈负相关，与木质部比导率呈正相关。因此，在水力安全性和生长之间存在权衡，但在水力安全性和效率之间没有权衡。最后，我们发现一些解剖结构特征，如导管密度和导管腔面积与次生木质部的比值，与栓塞抗性有关，而茎组织木质化则没有。现在需要进一步研究栓塞抗性的观察到的变异性与产量之间的联系，以促进确定改良产量的选育策略，以适应日益干旱的世界。
