在2004和2005年棉花生长季节,采用筒栽和大田小区试验相结合,对不同水分状况下茎直径微变化动态中日最大收缩量(M D S)、日增长量(D I)和当日复原所需时间(RT)等3个关键性指标进行了研究。结果表明,3个指标对植株体内水分状况变化的反...在2004和2005年棉花生长季节,采用筒栽和大田小区试验相结合,对不同水分状况下茎直径微变化动态中日最大收缩量(M D S)、日增长量(D I)和当日复原所需时间(RT)等3个关键性指标进行了研究。结果表明,3个指标对植株体内水分状况变化的反应均非常敏感,随着日出前叶水势的降低,M D S明显增大;D I逐渐减小,在水势较高时变化幅度较小;RT则大幅度延长。当叶水势降低到-0.1M Pa时,D I变为负值,RT维持在24 h。3个指标的株间变异性测定结果表明,M D S和D I均存在较大的株间变异系数,RT的变异系数最小。对RT与土壤相对含水率进行相关分析发现,两者之间呈幂函数关系,相关程度达极显著水平。根据RT与叶水势和土壤相对含水率的关系,确定了RT对应于棉花适宜水分、轻度水分胁迫和重度水分胁迫的变化范围,而且,在对应的土壤含水率范围内,RT维持在一个相对稳定的区间,说明RT可作为指导棉花灌溉的适宜指标。M D S和D I由于影响因素较多,难以确定对应于水分胁迫的临界值,不适于单独作为灌溉指标。展开更多
Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e...Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e.g. field capacity, infikration rates） effectively control the water re-distribution in the ecosystem, a fact that is aggravated in arid environments. Information of the spatial and temporal accessibility of soil water in desert ecosystems is limited. The purpose of the studies is the application of plant water potential to estimate the spatial and temporal variations of soil water availability in different arid ecosystems of the Negev （Israel） and southern Morocco. As model plants the evergreen shrubs Retama raetam, Thymelaea hirsuta and trees （Acacia tortilis） were chosen. Seasonal and spatial variations of the pre-dawn water potential （ψpd） were examined as diagnostic tool to determine water availability on the landscape level. The seasonal differences in the pre-dawn water potential were less pronounced on the dune compared to the interdune. This showed a better water availability on the dune slope. Also in the investigated wadis systems spatial differences of the water potential could be detected and related to the vegetation pattern.展开更多
The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions ...The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions of carob trees(Ceratonia siliqua L.)with 2-year-old from different climate regions to drought generated by four water treatments:Tc(250 mm),T1(180 mm),T2(100 mm),and T3(50 mm).The first accession(A1)comes from the protected national park of Ichkeul in northern Tunisia.This zone belongs to the bioclimatic sub-humid stage.The second accession(A2)comes from Melloulech,located in the center-east of Tunisia,belonging to the bioclimatic semi-arid stage.The third accession(A3)comes from the mountain of Matmata,located in the south of Tunisia,belonging to the bioclimatic hyper-arid stage.The experiment was undertaken in a greenhouse.Gaz exchange indices(net photosynthesis(A),stomatal conductance(gs),transpiration rate(E),and internal CO_(2) concentration(Ci))were determined.Predawn(Ψpd)and midday(Ψmd)leaf water potentials,relative soil water content(SWC),and morphological parameters(plant height(H),number of leaves(NL),number of leaflets(Nl),and number of branches(NB))were estimated.The results showed that significant differences(P<0.001)were found between physiological and morphological parameters of each accession.The highest growth potential was recorded for Tc treatment in both accessions A1 and A2.Significant decreases in gs,E,Ci,and SWC were recorded with the increases in water stress applied from treatment T1 to T3.Positive and significant correlations were found between SWC andΨpd for all studied accessions.Ψpd andΨmd decreased as water stress increased,ranging from–0.96 to–1.50 MPa at sunrise and from–1.94 to–2.83 MPa at midday,respectively,under control and T3 treatments.C.siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior.Both accessions A1 and A2 showed greater drought tolerance than accession A3.These seedlings exhibit different adaptive mechanisms such as stress avoidance,which are aimed at reducing transpiration,limiting leaf growth,and increasing root growth to exploit more soil water.Therefore,C.siliqua can be recommended for the ecological restoration in Mediterranean ecosystems.展开更多
文摘在2004和2005年棉花生长季节,采用筒栽和大田小区试验相结合,对不同水分状况下茎直径微变化动态中日最大收缩量(M D S)、日增长量(D I)和当日复原所需时间(RT)等3个关键性指标进行了研究。结果表明,3个指标对植株体内水分状况变化的反应均非常敏感,随着日出前叶水势的降低,M D S明显增大;D I逐渐减小,在水势较高时变化幅度较小;RT则大幅度延长。当叶水势降低到-0.1M Pa时,D I变为负值,RT维持在24 h。3个指标的株间变异性测定结果表明,M D S和D I均存在较大的株间变异系数,RT的变异系数最小。对RT与土壤相对含水率进行相关分析发现,两者之间呈幂函数关系,相关程度达极显著水平。根据RT与叶水势和土壤相对含水率的关系,确定了RT对应于棉花适宜水分、轻度水分胁迫和重度水分胁迫的变化范围,而且,在对应的土壤含水率范围内,RT维持在一个相对稳定的区间,说明RT可作为指导棉花灌溉的适宜指标。M D S和D I由于影响因素较多,难以确定对应于水分胁迫的临界值,不适于单独作为灌溉指标。
文摘Arid and semi-arid regions are characterized by low rainfall and high potential evaporative demand. Here, water is the major limiting factor for plant growth and productivity. Soil and surface hydrology properties （e.g. field capacity, infikration rates） effectively control the water re-distribution in the ecosystem, a fact that is aggravated in arid environments. Information of the spatial and temporal accessibility of soil water in desert ecosystems is limited. The purpose of the studies is the application of plant water potential to estimate the spatial and temporal variations of soil water availability in different arid ecosystems of the Negev （Israel） and southern Morocco. As model plants the evergreen shrubs Retama raetam, Thymelaea hirsuta and trees （Acacia tortilis） were chosen. Seasonal and spatial variations of the pre-dawn water potential （ψpd） were examined as diagnostic tool to determine water availability on the landscape level. The seasonal differences in the pre-dawn water potential were less pronounced on the dune compared to the interdune. This showed a better water availability on the dune slope. Also in the investigated wadis systems spatial differences of the water potential could be detected and related to the vegetation pattern.
文摘The greatest failure rate of reforestation programs is basically related to water deficit,especially at the seedling stage.Therefore,the main objective of this work is to investigate the responses of three accessions of carob trees(Ceratonia siliqua L.)with 2-year-old from different climate regions to drought generated by four water treatments:Tc(250 mm),T1(180 mm),T2(100 mm),and T3(50 mm).The first accession(A1)comes from the protected national park of Ichkeul in northern Tunisia.This zone belongs to the bioclimatic sub-humid stage.The second accession(A2)comes from Melloulech,located in the center-east of Tunisia,belonging to the bioclimatic semi-arid stage.The third accession(A3)comes from the mountain of Matmata,located in the south of Tunisia,belonging to the bioclimatic hyper-arid stage.The experiment was undertaken in a greenhouse.Gaz exchange indices(net photosynthesis(A),stomatal conductance(gs),transpiration rate(E),and internal CO_(2) concentration(Ci))were determined.Predawn(Ψpd)and midday(Ψmd)leaf water potentials,relative soil water content(SWC),and morphological parameters(plant height(H),number of leaves(NL),number of leaflets(Nl),and number of branches(NB))were estimated.The results showed that significant differences(P<0.001)were found between physiological and morphological parameters of each accession.The highest growth potential was recorded for Tc treatment in both accessions A1 and A2.Significant decreases in gs,E,Ci,and SWC were recorded with the increases in water stress applied from treatment T1 to T3.Positive and significant correlations were found between SWC andΨpd for all studied accessions.Ψpd andΨmd decreased as water stress increased,ranging from–0.96 to–1.50 MPa at sunrise and from–1.94 to–2.83 MPa at midday,respectively,under control and T3 treatments.C.siliqua accessions responded to drought through exhibiting significant changes in their physiological and morphological behavior.Both accessions A1 and A2 showed greater drought tolerance than accession A3.These seedlings exhibit different adaptive mechanisms such as stress avoidance,which are aimed at reducing transpiration,limiting leaf growth,and increasing root growth to exploit more soil water.Therefore,C.siliqua can be recommended for the ecological restoration in Mediterranean ecosystems.
