Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Ann Bot. 2019 Oct 29;124(4):617-626. doi: 10.1093/aob/mcz002.
The use of woody crops for Quad-level (approx. 1 × 1018 J) energy production will require marginal agricultural lands that experience recurrent periods of water stress. Populus species have the capacity to increase dehydration tolerance by lowering osmotic potential via osmotic adjustment. The aim of this study was to investigate how the inherent genetic potential of a Populus clone to respond to drought interacts with the nature of the drought to determine the degree of biochemical response.
A greenhouse drought stress study was conducted on Populus deltoides 'WV94' and the resulting metabolite profiles of leaves were determined by gas chromatography-mass spectrometry following trimethylsilylation for plants subjected to cyclic mild (-0.5 MPa pre-dawn leaf water potential) drought vs. cyclic severe (-1.26 MPa) drought in contrast to well-watered controls (-0.1 MPa) after two or four drought cycles, and in contrast to plants subjected to acute drought, where plants were desiccated for up to 8 d.
The nature of drought (cyclic vs. acute), frequency of drought (number of cycles) and the severity of drought (mild vs. severe) all dictated the degree of osmotic adjustment and the nature of the organic solutes that accumulated. Whereas cyclic drought induced the largest responses in primary metabolism (soluble sugars, organic acids and amino acids), acute onset of prolonged drought induced the greatest osmotic adjustment and largest responses in secondary metabolism, especially populosides (hydroxycinnamic acid conjugates of salicin).
The differential adaptive metabolite responses in cyclic vs. acute drought suggest that stress acclimation occurs via primary metabolism in response to cyclic drought, whereas expanded metabolic plasticity occurs via secondary metabolism following severe, acute drought. The shift in carbon partitioning to aromatic metabolism with the production of a diverse suite of higher order salicylates lowers osmotic potential and increases the probability of post-stress recovery.
利用木本作物进行四级（约 1×1018 J）能源生产将需要经历周期性水资源胁迫的边缘农业用地。杨树具有通过渗透调节降低渗透势来提高脱水耐受性的能力。本研究旨在探讨杨树无性系固有的抗旱遗传潜力与干旱的性质如何相互作用，以确定生化反应的程度。
在温室中对 Populus deltoides 'WV94'进行干旱胁迫研究，对经历周期性轻度（-0.5 MPa 黎明前叶片水势）干旱与周期性重度（-1.26 MPa）干旱的植株以及与充分供水对照（-0.1 MPa）的植株进行三甲基硅烷化处理后，通过气相色谱-质谱法确定叶片的代谢物谱，然后对植株进行两次或四次干旱循环，与急性干旱的植株相比，急性干旱的植株会在 8 天内干燥。
干旱的性质（周期性与急性）、干旱的频率（干旱周期的数量）和干旱的严重程度（轻度与重度）均决定了渗透调节的程度以及积累的有机溶质的性质。虽然周期性干旱诱导了初级代谢物（可溶性糖、有机酸和氨基酸）的最大响应，但急性长时间干旱的发生诱导了最大的渗透调节和次生代谢物的最大响应，特别是水杨苷（水杨酸的羟基肉桂酸轭合物）。
在周期性与急性干旱之间，适应代谢物响应的差异表明，应激驯化通过初级代谢物发生在周期性干旱的情况下，而在严重的急性干旱后，通过次生代谢物发生扩展的代谢可塑性。碳分配向芳香族代谢物的转变，产生了一系列不同的高级水杨酸盐，降低了渗透势，增加了应激后恢复的可能性。
