ABSTRACT The negative impact of water stress on forest and tree plantation productivity has been the focus of many investigations. However, moderate water stress that can decrease productivity and is difficult to detect, has received less attention. Therefore, we designed a greenhouse experiment where the main objective was to test the efficacy of published biochemical and water stress indices along with physiological traits in detecting moderate water stress at leaf scale. Potted saplings of three hybrid poplars ((Populus × canadensis) × P. maximowiczii, Populus × canadensis and Populus × generosa ‘Boelare’) were subjected to moderate water stress. During the experiment we recorded (i) the biomass accumulation and allocation to leaves, stem, and roots; (ii) Net CO2 assimilation rate (A) and stomatal conductance (g s) and (iii) Spectral biochemical and water indices. Results indicate that moderate water deficit had a negative impact on biomass accumulation, but no change was detected in physiological traits. Nitrogen and chlorophyll contents also remained unaffected. Spectral biochemical indices failed to detect differences between treatments, whereas water stress indices succeeded. We also have identified unique wavelengths in the shortwave infrared region of the spectrum that proved sufficiently sensitive on their own to detect moderate water deficit. The results were not influenced by a genotype effect, suggesting that these unique wavelengths could be responding to a general rather than a species-specific leaf feature, thus widening opportunities for the early detection of plant stress, particularly moderate water deficit.

中文翻译：

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在生理效应出现之前，利用三种杨树杂交种的叶片光谱响应检测植物水分胁迫

摘要 水资源压力对森林和人工林生产力的负面影响一直是许多调查的焦点。然而，可降低生产力且难以检测的适度缺水压力却很少受到关注。因此，我们设计了一个温室实验，其主要目的是测试已发表的生化和水分胁迫指数以及生理特征在检测叶尺度中度水分胁迫方面的功效。三种杂交杨树（(Populus × canadensis) × P. maximowiczii、Populus × canadensis 和 Populus × generosa 'Boelare'）的盆栽树苗受到中等水分胁迫。在实验过程中，我们记录了 (i) 生物量积累和分配到叶、茎和根；(ii) 净 CO2 同化率 (A) 和气孔导度 (gs) 和 (iii) 光谱生化和水指数。结果表明，中度缺水对生物量积累有负面影响，但生理性状没有变化。氮和叶绿素含量也不受影响。光谱生化指标未能检测到处理之间的差异，而水分胁迫指标却成功了。我们还确定了光谱的短波红外区域中的独特波长，这些波长本身就足够敏感，可以检测到中度缺水。结果不受基因型效应的影响，表明这些独特的波长可能对一般的而不是物种特异性的叶子特征做出反应，从而扩大了早期检测植物胁迫的机会，