J Plant Ecol ›› 2021, Vol. 14 ›› Issue (1): 117-131.DOI: 10.1093/jpe/rtaa080

• Research Articles • Previous Articles     Next Articles

Unexpectedly low δ 13C in leaves, branches, stems and roots of three acacia species growing in hyper-arid environments

Daphna Uni1,2,3 , Elli Groner2 , Elaine Soloway4 , Amgad Hjazin4 , Spencer Johnswick4 , Gidon Winters2 , Efrat Sheffer3 , Ido Rog1 , Yael Wagner1 and Tamir Klein1, *   

  1. 1 Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel, 2 The Dead Sea-Arava Science Center, Tamar Regional Council, Neve Zohar 86910, Israel, 3 Institute of Plant Sciences and Genetic in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel, 4 Arava Institute for Environmental Studies, Kibbutz Ketura, Israel

    *Corresponding author. E-mail: tamir.klein@weizmann.ac.il
  • Received:2020-07-27 Revised:2020-09-05 Accepted:2020-10-13 Online:2020-11-21 Published:2021-02-01

Abstract:

Aims

In plant eco-physiology, less negative (enriched) carbon 13 (13C) in the leaves indicates conditions of reducing leaf gas exchange through stomata, e.g. under drought. In addition, 13C is expected to be less negative in non-photosynthetic tissues as compared with leaves. However, these relationships in δ 13C from leaves (photosynthetic organs) to branches, stems and roots (non-photosynthetic organs) are rarely tested across multiple closely related tree species, multiple compartments, or in trees growing under extreme heat and drought.

Methods

We measured leaf-to-root 13C in three closely related desert acacia species (Acacia tortilisA. raddiana and A. pachyceras). We measured δ 13C in leaf tissues from mature trees in southern Israel. In parallel, a 7-year irrigation experiment with 0.5, 1.0 or 4.0 L day−1 was conducted in an experimental orchard. At the end of the experiment, growth parameters and δ 13C were measured in leaves, branches, stems and roots.

Important Findings

The δ 13C in leaf tissues sampled from mature trees was ca. −27‰, far more depleted than expected from a desert tree growing in one of the Earth’s driest and hottest environments. Across acacia species and compartments, δ 13C was not enriched at all irrigation levels (−28‰ to ca. −27‰), confirming our measurements in the mature trees. Among compartments, leaf δ 13C was unexpectedly similar to branch and root δ 13C, and surprisingly, even less negative than stem δ 13C. The highly depleted leaf δ 13C suggests that these trees have high stomatal gas exchange, despite growing in extremely dry habitats. The lack of δ 13C enrichment in non-photosynthetic tissues might be related to the seasonal coupling of growth of leaves and heterotrophic tissues.

Key words: stable isotope, δ?13C enrichment, desert, tree drought resistance, Acacia raddiana, Acacia tortilis

摘要:
生长在超干旱环境下的3种相思树种表现出异常低的叶片、树枝、树干、根中δ13C含量
在植物生理生态学中,叶片中碳13(13C)含量负值较少(富集),表明叶片处于通过气孔的气体交换减少,比如在干旱胁迫下。此外,与叶片相比,13C在非光合组织中的负值也较少。然而,对从叶片(光合器官)到树枝、树干和根(非光合器官)中的δ 13C数值的关系知之甚少,特别是缺少在关联密切的多个树种间或者不同器官间,以及对生长在极端高温和干旱胁迫下的树木中进行测定。本研究测定了3种近缘沙漠相思树种(Acacia tortilis、A. raddiana和A. pachyceras)从叶片到根的13C含量。我们在以色列南部成树的叶片组织中测定了δ 13C含量。与此同时,在试验果园进行了为期7年的3个水平的灌溉试验。在试验结束时,测定了叶片、树枝、树干和根的生长参数和δ 13C含量。研究结果表明,叶片组织中δ 13C含量约为−27‰,其同位素贫化程度远超过生长在地球上最干燥和最热环境中的沙漠树种的预期值。在不同的相思树种和不同器官中,所有灌溉水平处理中的δ 13C含量并没有富集(−28‰到ca. −27‰),证实了在成熟相思树中的测定结果。在不同器官中,叶片δ 13C含量与树枝和根的δ 13C含量异常相似,甚至比树干的δ 13C含量负值更少。高度贫化的叶片δ 13C表明,尽管这些树木生长在极端干燥的生境中,但其气孔气体交换较高。非光合组织中缺乏δ 13C富集可能与叶片和异养组织生长的季节耦合有关。

关键词: 稳定性同位素, 13C富集, 沙漠, 树木抗旱性, 相思树属