J Plant Ecol ›› 2020, Vol. 13 ›› Issue (4): 389-397.DOI: 10.1093/jpe/rtaa017

• Research Articles • Previous Articles     Next Articles

The role of soluble sugars during drought in tropical tree seedlings with contrasting tolerances

Michael J. O’Brien1,2, *, Annabelle Valtat3, Samuel Abiven4,5,6 , Mirjam S. Studer4 , Robert Ong7 and Bernhard Schmid3,4   

  1. 1 Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, c/Tulipán s/n., E-28933 Móstoles, Madrid, Spain, 2 Southeast Asia Rainforest Research Partnership, The Peak Vista, Lorang Punjak 1, Tanjung Lipat, Kota Kinabalu, Sabah 88400, Malaysia, 3 Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland, 4 Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland, 5 Laboratoire de Géologie, UMR 8538, Ecole Normale Supérieure, PSL Research University, CNRS, Paris, France, 6 Centre de recherche en écologie expérimentale et prédictive (CEREEP-Ecotron IleDeFrance), Département de biologie, Ecole normale supérieure, CNRS, PSL University, 77140, St-Pierreles-Nemours, France, 7 Forest Research Centre, Sepilok, 90715 Sandakan, Sabah, Malaysia

    *Corresponding author. E-mail: mikey.j.obrien@gmail.com
  • Received:2020-03-25 Accepted:2020-04-09 Online:2020-04-13 Published:2020-08-01

Abstract:

Aims

Non-structural carbohydrates (NSCs) are plant storage compounds used for metabolism, transport, osmoregulation and regrowth following the loss of plant tissue. Even in conditions suitable for optimal growth, plants continue to store NSCs. This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth. The former pathway implies that NSCs may be a by-product of sink limitation, while the latter suggests a functional role of NSCs for use during poor conditions.

Methods

Using 13C pulse labelling, we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought. We monitored growth, stomatal conductance, stem water potential and NSC storage to assess a broad carbon response to drought.

Important Findings

We found that the drought-sensitive species had reduced growth, conserved NSC concentrations in leaf, stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions. In contrast, the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings. These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition, while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs. These strategies seem correlated with baseline maximum growth rates, which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.

Key words: 13C labelling, carbohydrate storage,  drought tolerance,   hydraulic function,   Shorea parvifolia,,   Shorea beccariana,   source–sink allocation

摘要:
非结构碳水化合物(NSCs)是植物的贮藏化合物,用于代谢、运输、渗透调节和叶片脱落后的再生。即使在最适宜生长的条件下,植物也会继续储存NSCs。这种储存可能是由于生长受到抑制而产生的被动积累,也可能是由于以生长为代价而产生的主动储备。前者暗示NSCs可能是碳汇有限生长的副产物,而后者则表明NSCs在植物适应逆境中具有的功能作用。本研究中,利用 13C脉冲标记,我们追踪了具有不同干旱耐受性的两种热带树种的幼苗在干旱和常湿条件下茎和根器官中可溶性糖的来源,以估计干旱前储存的NSCs与干旱期间同化的NSCs的相对分配。我们监测了生长、气孔导度、茎干水势和NSC储存以评估对干旱的全碳响应。结果表明,与对照幼苗相比,不耐旱树种生长速度减慢,在叶片、茎和根器官中储存NSCs,在茎和根器官中可溶性糖(源于干旱前的储存)的比例更大。相反,与对照幼苗相比,耐旱树种则能保持生长和茎根NSCs浓度,但叶片NSCs浓度降低,茎和根可溶性糖的比例更大,这些可溶性糖来自于新同化的光合产物。这些结果表明,不耐旱树种由于缺水导致生长受限而被动积累NSCs,而耐旱树种则通过分配NSCs到茎和根器官来积极响应缺水。这些策略似乎与基线最大生长速率相关,并且支持了以前的研究结果,表明在生长和耐旱性之间存在一种权衡关系,同时也为NSCs分配的可塑性在干旱中的重要性提供了新的证据。

关键词: 13C标记,  耐旱性,   碳水化合物储存,   水力学功能,   娑罗双属植物,   源汇分配