Assessing environmental controls over conductances through the soil–plant–atmosphere continuum in an experimental olive tree plantation of southern Italy
Assessing environmental controls over conductances through the soil–plant–atmosphere continuum in an experimental olive tree plantation of southern Italy
复制标题
DOI：
10.1016/j.agrformet.2009.02.008
复制
发表时间：
2009-08
影响因子：
6.2
通讯作者：
R. Tognetti;A. Giovannelli;A. Lavini;G. Morelli;F. Fragnito;R. D’andria
中科院分区：
文献类型：
--
作者：
R. Tognetti;A. Giovannelli;A. Lavini;G. Morelli;F. Fragnito;R. D’andria
研究了果园栽培油橄榄（Olea europaea L.）树木水分状况和水分利用指标的制约因素。Nocellara del Belice，以评估生产力和干旱适应能力。这项研究是对16岁的嫁接植物进行的，这些植物在意大利南部的一个试验点种植园中，在不同的水处理下生长了14年。水处理为：不灌溉、雨养、对照（T0）和3个处理，从果核硬化开始到果实成熟早期（分别为T33和T66），每个处理的季节性水量相当于作物蒸散量（ETC）的33%和66%，整个灌溉季节（T100）的蒸散量为100%。在2006年和2007年的生长季，采用自动点式树木测量仪测量植株茎半径变化，并采用补偿热脉冲技术测定整个植株的水分利用。额外的生理生态参数，如气孔导度和水势，以及营养发育定期测量。雨养树木黎明前叶片水势下降，这与土壤水分亏缺增加有关，而黎明前和正午叶片水势的差异增加，表明植物水势的各向异性调节。橄榄树对蒸腾有严格的气孔控制，但在严重干旱胁迫下不足以防止水力导度的损失。在温和年份（2006年），不同水分处理之间的茎径向增量和树液通量没有一致性差异，而在干旱年份（2007年），灌溉树木的用水量高于雨养树木。然而，在旱期，旱作条件下生长的植株的最大日收缩量比灌溉条件下的植株略有增加，尽管灌溉处理之间没有显著差异。2006年的平均日蒸腾速率、冠层导度和解耦系数均高于最干旱的2007年，且完全灌溉的植物高于旱作植物。这些结果支持了雨养树木比灌溉树木具有更保守的用水策略的观点，并且亏缺灌溉的树木在功能和结构上适应了长期的部分浇水。基于这些观察结果，我们可以认为，在土壤逐渐干燥的条件下，水力导度的损失是增加气孔对蒸腾控制的重要机制。另一种观点认为，夏季土壤和叶片水势差的增加导致气孔关闭，使传导系统崩溃的风险最小化，从而减少了蒸腾和水力传导。
Constraints on plant water status and water use indicators were studied in orchard grown Olea europaea L. trees, cv. Nocellara del Belice, in order to assess productivity and drought adaptation. The study was conducted on 16-year-old grafted plants, grown under different water treatments for 14 years in an experimental site plantation in southern Italy. Water treatments were: a non-irrigated, rainfed, control (T0) and three treatments that received seasonal water amount equivalent to 33 and 66% of crop evapotranspiration (ETC) from the beginning of pit hardening to early fruit veraison (respectively T33 and T66), and 100% of ETCthroughout the irrigation season (T100). During 2006 and 2007 growing seasons, plants were continuously monitored by automatic point dendrometers measuring stem radius variation and whole-plant water use was determined using a xylem sap flow method (compensation heat-pulse technique). Additional ecophysiological parameters, such as stomatal conductance and water potentials were periodically measured, as well as vegetative development. Predawn leaf water potential decreased in rainfed trees and this was associated with increasing soil moisture deficit, while the difference between predawn and midday leaf water potentials increased, suggesting anisohydric regulation of plant water potential. Olive trees exhibited a tight stomatal control over transpiration, but insufficient to prevent loss of hydraulic conductance under severe drought stress. The stem radial increment and sap flux did not differ consistently between water treatments in the mild year (2006), while irrigated trees had higher water use than rainfed trees in the dry year (2007). However, plants growing under rainfed conditions showed a small increase in maximum daily shrinkage during drought periods compared to irrigated ones, although no marked differences were recorded between irrigated treatments. The mean daily transpiration rate, canopy conductance and decoupling coefficient were higher in 2006 than in 2007, the driest year, only, and in fully irrigated rather than rainfed plants. These results support the idea that rainfed trees had more conservative water use strategies than irrigated trees, and that deficit-irrigated trees acclimated somewhat functionally and structurally to long-term partial watering. Based on these observations, we can argue that loss of hydraulic conductance is an important mechanism for increasing stomatal control of transpiration under progressive soil drying. Another view implies that the increasing difference between soil and leaf water potential during summer induced stomatal closure and minimized the risk of a collapse of the conductive system, decreasing transpiration and reducing hydraulic conductance.