J Plant Ecol ›› 2020, Vol. 13 ›› Issue (3): 304-312.DOI: 10.1093/jpe/rtaa015

• Research Articles • Previous Articles     Next Articles

Decoupled drought responses of fine-root versus leaf acquisitive traits among six Prunus hybrids

Shuang-Xi Zhou1, *, Rob R. Walker and Everard Edwards   

  1. CSIRO Agriculture and Food, Glen Osmond, SA 5064, Australia
    1 Present address: The New Zealand Institute for Plant and Food Research Ltd, Hawke’s Bay, New Zealand
    *Corresponding author. E-mail: Shuangxi.Zhou@plantandfood.co.nz
  • Received:2019-12-30 Revised:2020-03-02 Accepted:2020-04-09 Online:2020-04-13 Published:2020-06-01

Abstract:

Aims

Predicting drought consequences on forests and fruit crop plantings requires improved understanding of drought responses of both leaf and fine-root resource acquisitive traits (specific leaf area—SLA, specific root surface area—SRA and specific root length—SRL). We hypothesize their responses are coordinated towards integrated plant resource conservation under severe drought.

Methods

We tested the hypothesis with a greenhouse-based drought experiment on saplings of six Prunus hybrids with a priori known contrasting drought sensitivity. Saplings were subjected to either control (100% field capacity) or severe drought stress treatment (33% evapotranspiration of hybrid-specific control plants). Sample collections were carried out at 30 and at 60 days after the start of treatments, for both control and stressed saplings.

Important Findings

No hybrid showed concurrent significant decrease of SLA and SRA (or SRL) under severe drought. The fine-root traits of the six hybrids showed two major drought-response scenarios, in particular: (i) increased root tissue density (RTD) and decreased average root diameter without significant change of SRL and (ii) increased RTD and decreased SRL without significant change of average root diameter. Drought responses of leaf gas exchange, SRA, SRL and RTD were closely correlated along a gradient towards resource conservation from control to drought-stressed plants in all hybrids, which was orthogonal to another gradient characterized by a hybrid-dependent decrease of SLA. These findings highlight (i) the multi-dimensionality of root-trait drought responses, (ii) the decoupling between leaf economics and leaf hydraulics and (iii) the covariation of leaf and root hydraulics in terms of trait drought responses. The study contributes to identifying the origin of the multi-dimensionality of root-trait drought response at intraspecific scale, and highlights differential drought–response combinations of leaf and fine-root traits among hybrids to survive under severe soil drought stress.

Key words: multi-dimensional drought response, soil water stress, specific leaf area, specific root length, specific root surface area

摘要:

要预测干旱对森林和果树种植的影响,就需要更好地了解干旱胁迫对叶片和细根的资源获取性状(比叶面积SLA、比根面积SRA以及比根长SRL)的影响。本研究试图验证以下科学假设:在重度干旱胁迫下,叶片与细根的资源获取性状具有协同效应,使得植物能够采取整合的资源节约策略。我们收集了不同干旱敏感性的六种李属砧木的幼树,通过在温室中对它们进行干旱试验来验证我们的科学假设。这些幼树被分为两组进行水分处理试验,即对照处理组(浇水量为100%田间持水量)与重度干旱处理组(每种砧木的浇水量为该砧木对照组植物每日蒸散量的33%)。在处理开始后的第30天和第60天,分别对两组处理下的六种砧木的植物叶片与细根进行取样。结果表明,在重度干旱胁迫下,没有任何一种植物同时显著降低了SLA和SRA(或SRL)。六种李属砧木植物的细根性状表现出两种主要的干旱响应组合:(1)根组织密度(RTD)增大,同时平均根径减小,而SRL没有显著变化;(2) RTD增大,同时SRL减小,而平均根径没有显著变化。六种砧木植物性状的干旱响应展现出两个相互垂直的变化梯度,这两个梯度均以从对照处理组到干旱处理组植物的资源节约性变化为特征,其中一个梯度展现了叶片气体交换,SRA,SRL以及RTD的干旱响应之间的密切相关关系,而另一个梯度以SLA的降低为特征。这些发现突出了(1)根系性状干旱响应的多维性;(2)重度干旱胁迫下,叶片经济性状与叶片水力性状之间的解耦联关系;(3)重度干旱胁迫下,叶片水力性状与根系水力性状之间的协同变化关系。这项研究有助于在种内尺度上确认根系干旱响应多维性的起源,并重点突出了不同植物如何通过不同的叶片与细根性状的干旱响应组合而得以在重度干旱胁迫下存活。

关键词: 多维度干旱响应, 土壤水分胁迫, 比叶面积, 比根长, 比根表面积