干旱胁迫对欧李幼苗表型可塑性的影响

该研究以欧李为材料,探讨了干旱胁迫对欧李表型可塑性的影响。结果表明:(1)随着干旱胁迫的加剧,欧李根生物量、枝叶生物量、植株总生物量积累、根冠比和根冠比胁迫指数均呈现先升高后降低的趋势,在T1处理下达到最大值,并显著高于其他处理(α=0.05)。(2)随土壤含水量的降低,欧李根的生物量分配指数呈现先增加后降低的趋势,叶生物量与之相反,在T1处理下根的生物量分配指数最大,枝叶的最小(α=0.05)。(3)在水分供应为60%～80%时,欧李的株高、冠幅、基径、二级分枝数、主根长、主根直径及侧根数量均达到最大值(α=0.05),对一级分枝数的生长没有显著影响。(4)随着水分胁迫的加剧,叶片长从T2处理开始下降,叶片宽、单片叶面积及比叶面积均呈现先增加后减少的趋势(α=0.05)。综上可得,欧李通过调整形态特性和各器官生物量积累及其分配对不同干旱胁迫条件产生了较强的可塑性。     

干旱胁迫对条墩桑生物量分配和光合特性的影响

以1年生红皮花桑为材料,采用盆栽的方法,研究了不同水分条件下条墩桑幼苗的生物量、荧光参数、净光合速率、气孔导度、蒸腾速率及水分利用效率的变化.结果表明： 随着干旱胁迫程度的增加,植株地上部分的生物量和总生物量逐渐降低,但光合产物向根部的分配比例逐渐增大,根冠比逐渐增加;叶片的荧光参数F_o、F_v和F_v/F_m逐渐降低;气孔导度、蒸腾速率、净光合速率和水分利用效率逐渐下降.     

干旱胁迫对蒙古黄芪生物量及其根际微生物种群数量的影响

以‘武川’和‘浑源’2个蒙古黄芪地方品种为试材,采用盆栽控水模拟干旱处理,研究干旱胁迫下黄芪生物量及根际微生物数量的动态变化规律。结果显示：随着干旱程度的加剧,2个品种的根际细菌和放线菌种群数量均呈先上升后下降的变化趋势,真菌数量却呈现持续减少,而细菌数量在根际微生物区系中占绝对优势;随干旱强度升高,2个品种黄芪根、叶组织相对含水量均表现出明显的逐渐下降趋势,其地上部生物量、根系生物量也均降低,而根冠比却逐渐增大;黄芪根际各菌类数量与其地上生物量存在显著正相关关系,但与根系生物量无显著相关关系。研究表明,黄芪的生长及其根际微生物数量均受到干旱胁迫的影响,且适度干旱有助于提高黄芪根际细菌及放线菌的数量,从而改变根际微生物群落结构组成,促进黄芪地上生物量的积累。     

去除顶端优势对菊芋器官C、N、P化学计量特征的影响

以不同时期顶端优势去除处理的菊芋为研究对象,通过测定根、茎、叶、花和块茎等器官C、N、P含量,计算C∶N、C∶P和N∶P比值,探讨顶端优势去除对菊芋各器官C、N、P化学计量特征的影响规律。结果表明:各器官之间C含量高低顺序没有因去顶而改变,氮和磷含量高低顺序因去顶而表现出不同的大小关系;顶端优势去除提高了茎秆、块茎和分枝的C含量,除最后一次顶端优势去除提高了叶片C含量,其它顶端优势去除时间均降低了叶片含量;顶端优势去除降低了根系、茎秆和块茎N含量,提高了分枝和花的含N量;顶端优势去除提高了叶片和块茎的含P量;C∶N范围为24.15—153.75、C∶P范围为118.87—2265.72、N∶P范围为2.46—24.05,N∶P平均值为10.67,说明菊芋生长主要受N元素的限制。     

干旱胁迫对多花黄精叶片光合特性的影响

以3年生多花黄精实生苗为材料,通过盆栽控水方式设置对照(80%土壤含水量)、轻度干旱(65%土壤含水量)、中度干旱(50%土壤含水量)和重度干旱(35%土壤含水量)4个处理,研究干旱胁迫对多花黄精叶片光合特性的影响,探讨多花黄精光合特性对干旱胁迫的响应规律。结果表明：(1)随着干旱胁迫程度的加深,多花黄精叶片叶绿素(a+b)含量、叶绿素b含量均呈先升高后下降的变化趋势,叶绿素a含量却逐渐下降,叶绿素a/b值和类胡萝卜素含量则呈“升高-下降-升高”的变化趋势。(2)多花黄精叶片净光合速率日变化在正常和轻度干旱胁迫条件下呈“单峰”曲线,而在中度和重度干旱胁迫条件下则表现为“双峰”曲线,且其“光合午休”现象的主要影响因素为非气孔限制。(3)随着干旱胁迫程度的加深,多花黄精叶片净光合速率、蒸腾速率、气孔导度、光能利用效率日均值均随之下降,但其水分利用效率日均值却随之上升。(4)随着干旱胁迫程度的加深,多花黄精的光补偿点先降低再急剧增加,而光饱和点则呈先增加再降低的变化趋势,且其表观量子效率逐渐降低;同时,其CO₂补偿点和CO₂饱和点均随着干旱胁迫程度...     

种子大小和干旱胁迫对辽东栎幼苗生长和生理特性的影响

在温室内遮阴条件下,设置80%、60%、40%和20%田间持水量(对照、轻度、中度和重度干旱)4个处理,研究种子大小和干旱胁迫对盆栽辽东栎幼苗生长和生理特性的影响。结果表明: 大种子(3.05±0.38 g)幼苗的单株叶面积、总干质量和根冠比在所有处理均显著大于小种子(1.46±0.27 g)幼苗,前者的株高、基径、叶片数、比叶面积、相对生长率和净同化率等生长参数在轻度、中度和重度干旱处理均不同程度大于后者。大种子幼苗叶片过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均高于小种子幼苗,前者叶片丙二醛(MDA)、可溶性蛋白、游离脯氨酸含量和叶绿素总量在部分干旱处理显著大于后者。除根冠比外,其他生长参数均随干旱胁迫增强逐渐减小,重度干旱处理大、小种子幼苗总干质量分别比对照降低19.4%和20.0%。POD、CAT和SOD活性均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗POD活性分别显著高于对照126.7%和142.1%,CAT活性分别显著高于对照170.0%和151.9%。在重度干旱处理,大、小种子幼苗MDA含量分别显著高于对照86.5%和68.9%。可溶性蛋白、游离脯氨酸含量和叶绿素总量均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗可溶性蛋白含量分别显著高于对照320.7%和352.7%。辽东栎大种子幼苗可依赖其生长和生理方面的优势比小种子幼苗具有更强的干旱耐受性,在退化次生林人工辅助实生更新中应优先选用抗逆性更强的大种子幼苗。     

萌芽菊芋块茎对盐碱土壤胁迫的生理响应

土壤盐碱化是影响全球农业生产和生态环境的重要问题。在农田、轻度盐碱草地和重度盐碱草地设置样地以块茎种植菊芋,次年5月块茎萌发阶段取块茎样品测定丙二醛、游离脯氨酸、可溶性糖含量以及抗氧化酶活性并进行蛋白质组学分析,分析了萌芽菊芋块茎对盐碱土壤胁迫的生理响应。0—20 cm土层的电导率(表征土壤可溶盐含量)表明从农田到轻度、重度盐碱草地土壤盐碱胁迫逐渐增强,丙二醛含量变化反映出菊芋块茎受害程度逐渐增加,并且基于游离脯氨酸的渗透调节能力也在逐渐增强。蛋白质组学分析结果显示与遗传信息加工相关的差异蛋白数量最多(占28.75%)且多为表达上调,意味着DNA复制和转录、蛋白质合成和折叠的相关蛋白在响应盐碱胁迫中发挥关键作用。碳水化合物及多糖代谢(占15%)、氨基酸代谢(占11.25%)以及能量代谢(占7.5%)相关的差异蛋白数量也较多,说明调节物质代谢平衡在萌芽菊芋块茎应对盐碱土壤胁迫过程中有重要作用。这些结果为揭示萌芽菊芋块茎适应盐胁迫的生理机制奠定了基础。     

土壤干旱对黄土高原4个乡土树种生长及干物质分配的影响

研究了不同土壤水分条件对黄土高原4个乡土树种幼苗生长及干物质分配的影响.结果表明,中度干旱(50%～55%θf)下虎榛子(Ostryopsis davidiana Decne.)和白刺花(Sophora viciifolin Hance)的生物量比适宜水分下(70%～75%θf)增加20.23%和3.93%,而大叶细裂槭(Acer stenolobum Rehd.var.megalophyllum Fang et Wu)和辽东栎(Quercus liaotungensis Koidz.)生物量分别降低13.59%和35.25%;重度干旱(40%～45%θf)对幼苗生长均有明显抑制作用.白刺花地上部与地下部的生长受水分胁迫影响较小,较其他树种具有更强的耐旱性;干旱对辽东栎地上部生长的影响较地下部大,重度干旱下其生长明显受抑制.随干旱程度加剧幼苗的根冠比增大,在重度干旱下大叶细裂槭根冠比达2以上.虎榛子整体生长速度较慢,对干旱的适应可能更多表现在生理上的耐旱.     

白刺花幼苗对不同强度干旱胁迫的形态与生理响应

为了探讨白刺花 (Sophora davidii (Franch.) Skeels) 幼苗对持续干旱胁迫的适应能力及对策,用盆栽方法人工模拟土壤干旱条件,设置土壤田间持水量 (WHC) 100%、80%、60%、40%和20% 5个干旱胁迫处理,研究了幼苗生长、生物量分配、水分利用效率 (WUE) 、叶形态解剖结构以及光合色素等在不同干旱胁迫强度下的变化特点.结果显示,胁迫处理96d后,100% WHC条件下白刺花幼苗的总叶面积、分枝数、基径及最大根长等均最大;80% WHC对幼苗产生了轻度胁迫,随着干旱胁迫强度的进一步增加,幼苗生长显著减小.干旱胁迫限制了新生叶发生与单叶面积扩展,导致冠层总叶面积减小,从而引起幼苗光合能力及生物量积累均降低.随着胁迫强度的增加,叶生物量所占的比例及叶面积/根生物量的比值都明显减小,而根生物量所占的比例增大,这说明叶生长对干旱胁迫反应比根更加敏感.另外,干旱胁迫下WUE随着生物量与耗水量的减小而降低,表明幼苗具有浪费型水分利用对策.叶绿素 (Chla、Chlb和Chla+b) 及类胡萝卜素含量 (Car) 都随着干旱胁迫增强而呈增大趋势,但Chla/b及 Chl/Ca变化趋势相反.干旱胁迫对叶片解剖结构影响较小,土壤水分减少时仅栅栏组织厚度略有增厚,海绵组织变薄.研究结果证明,60% WHC是幼苗生长、生物量积累、WUE和光捕获复合体活性受到明显抑制的干旱胁迫强度阈值;20% WHC胁迫处理对幼苗产生了严重危害.但是在实验过程中,即使在20%WHC条件下也未出现叶片凋落及幼苗死亡,表明当年生白刺花具有较强的干旱忍受能力,幼苗通过减小地上蒸发面积、增加地下生长及叶绿素含量等多种形态与生理策略适应干旱胁迫.     

盐胁迫对3种华南园林植物元素特性的影响

为筛选耐盐园林植物,研究了盐胁迫下狗牙花(Ervatamia divaricate)、红背桂(Excoecaria cochinchinensis)和花叶假连翘(Duranta erecta)的养分积累和分配规律。结果表明,盐胁迫增加了所有植物器官的Na和叶片K含量、狗牙花和红背桂各器官的Cl和N含量,但降低了所有植物枝干、红背桂和花叶假连翘根的K含量;各植物的P含量变化各异。盐胁迫增加了所有植物Na和Cl的积累量,并富集于枝干和叶片;狗牙花和花叶假连翘各器官的N、P和K积累量及红背桂各器官的P和K积累量随着Na Cl的浓度增加而下降。总之,盐胁迫使植物Na和Cl含量和积累量升高,而各器官生物量以及N、P和K积累量下降。3种植物中,狗牙花和花叶假连翘能更好地适应华南地区盐胁迫环境。     

膜下滴灌对棉花根系、地上部分生物量及产量的影响

通过膜下滴灌田间试验,采用根钻双向采样法,研究了不同灌溉量（2618、2947、3600和4265 m³·hm^-2）对棉花根系分布、地上部分生长及产量的影响.结果表明：不同灌溉量影响棉花根系及地上部分生长状况.各水分处理棉花根系主要分布在膜下,占根系总生物量的60.65%～73.45%,而膜间占39.35%～26.55%.水分亏缺增加了根系下扎深度和深层根系生物量,增大了根系水平分布范围.不同水分处理棉花生物学特性及干物质累积与分配存在显著差异.水分过量处理（4265 m³·hm^-2）的棉花株高、倒四叶宽、果枝数、蕾数均增加,干物质积累速率加快,根冠比及干物质在营养器官中的分配比例增大,生物产量提高,但同时蕾铃脱落率也增加,经济产量的形成受到抑制.水分亏缺或过量都影响棉花干物质在不同器官及不同生育时期的累积与分配,使产量降低.本试验条件下3600 m³·hm^-2是最适宜的灌溉量.     

部分根区灌溉与合理密植对旱区棉花产量和水分生产率的影响

为揭示部分根区灌溉与合理密植在棉花产量和水分生产率上的互作效应及其生理学机制,探索旱区节水灌溉植棉的新途径,在内蒙古自治区西部大田条件下,采用两因子试验设计研究了灌溉方式(常规灌溉、亏缺灌溉、部分根区灌溉)和种植密度(13.5万、18.0万、22.5万株·hm^-2)对棉花生长发育、产量、水分生产率和相关生理指标的影响.结果表明: 灌溉方式和种植密度及其互作对棉花生物产量、籽棉产量、产量结构和收获指数有显著影响.常规灌溉条件下,提高密度能显著提高生物产量和单位面积铃数,但铃重和收获指数显著降低,高密度与中等密度下的经济产量相当,并显著高于低密度处理;部分根区灌溉可显著提高棉花叶片中脱落酸(ABA)含量,并显著降低吲哚乙酸(IAA)含量,促进同化物向生殖器官的分配,提高收获指数.随着种植密度的提高,部分根区灌溉下单位面积铃数增加、铃重基本不变,高密度较中、低密度籽棉分别增产6.7%和11.5%.高密度下,部分根区灌溉与常规灌溉的籽棉产量相当,霜前花率提高22.5%,节水30%,水分生产率提高49.3%.种植密度对主茎功能叶光合速率没有显著影响,灌溉方式对光合速率有显著影响,亏缺灌溉显著降低了主茎功能叶的光合速率,而部分根区灌溉的叶片光合速率与常规灌溉相当.部分根区灌溉灌水侧根系茉莉酸(JA)含量和水通道蛋白基因(PIP)表达量显著高于常规灌溉,表明部分根区灌溉下,JA作为信号分子参与了灌水侧根系水分吸收的调控,PIP基因上调表达,根系吸水能力增强,保障了地上部叶片的水分平衡,进而维持了较高的光合速率.部分根区灌溉配合适当密植(22.5万株·hm^-2)是旱区节水植棉的重要技术途径.     

Effects of partial root-zone irrigation on hydraulic conductivity in the soil-root system of maize plants

Effects of partial root-zone irrigation (PRI) on the hydraulic conductivity in the soil-root system (L(sr)) in different root zones were investigated using a pot experiment. Maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed PRI, FPRI), or alternately on one of two sides (alternate PRI, APRI). Results show that crop water consumption was significantly correlated with L(sr) in both the whole and irrigated root zones for all three irrigation methods but not with L(sr) in the non-irrigated root zone of FPRI. The total L(sr) in the irrigated root zone of two PRIs was increased by 49.0-92.0% compared with that in a half root zone of CI, suggesting that PRI has a significant compensatory effect of root water uptake. For CI, the contribution of L(sr) in a half root zone to L(sr) in the whole root zone was ～50%. For FPRI, the L(sr) in the irrigated root zone was close to that of the whole root zone. As for APRI, the L(sr) in the irrigated root zone was greater than that of the non-irrigated root zone. In comparison, the L(sr) in the non-irrigated root zone of APRI was much higher than that in the dried zone of FPRI. The L(sr) in both the whole and irrigated root zones was linearly correlated with soil moisture in the irrigated root zone for all three irrigation methods. For the two PRI treatments, total water uptake by plants was largely determined by the soil water in the irrigated root zone. Nevertheless, the non-irrigated root zone under APRI also contributed to part of the total crop water uptake, but the continuously non-irrigated root zone under FPRI gradually ceased to contribute to crop water uptake, suggesting that it is the APRI that can make use of all the root system for water uptake, resulting in higher water use efficiency.     

塔克拉玛干沙漠腹地梭梭幼苗根系分布特征对不同灌溉量的响应

在塔克拉玛干沙漠腹地,采用分层分段挖掘法对不同灌溉量条件下(每株每次灌水35、24.5和14 kg)梭梭(Haloxylon ammodendron)幼苗根系的分布特征进行了研究。结果表明: 1)随着灌溉量的减少,梭梭幼苗根系生物量的分布格局有向深层发展的趋势,在不同灌溉量条件下地下垂直各层生物量与土壤垂直深度呈显著的负对数关系;2)各灌溉量梭梭幼苗的最大水平根长为垂直根长的2倍,但不同灌溉量根系生物量的水平分布趋势一致;3)吸收根生物量的垂直分布与土壤含水量的垂直变化基本一致,均呈“单峰型”曲线,但灌溉量不同,吸收根生物量峰值在土壤中出现的位置也不同,随着灌溉量的减少,吸收根集中分布区有向深层发展的趋势;4)根长、根表面积和根体积随着土壤深度的增加均呈“单峰型”曲线,灌溉量愈小,根长、根表面积和根体积的峰值愈位于土壤的深层;5)根冠比和垂直根深与株高之比随着灌溉量的减少而呈增加的趋势。     

Root, shoot tissues of Brassica juncea and Cereal secale promote potato health

Brassica species are increasingly being used as cover crops to suppress soil-borne diseases in potato cropping systems. Experiments were conducted in controlled environments and in the field to evaluate the effects of cover crop root or shoot or a combination of root and shoot tissues on potato root and tuber health. In a lab assay we examined the extent to which volatile compounds released from tissues of two cover crop species, rye (Cereale secale L.) and oriental mustard (Brassica juncea L.), could inhibit mycelium growth of two important potato diseases, Rhizoctonia solani and Pythium ultimum. Twenty-four hours into the lab assay, volatile compounds from all residues suppressed fungal growth. After 48 h, marked suppression of hyphal growth continued in the presence of mustard residues but not in the presence of rye tissues or the control without tissues. A 75 L volume container experiment evaluated the effect of incorporating different quantities of mustard shoot and root tissues (none, comparable to field level and fourfold field level) into R. solani and P. ultimum infested soil on potato growth, root health and tuber disease. In the container study, incorporating mustard shoots at the highest dose increased potato yield by 54% and reduced disease rating to 2.3 compared to a severe rating of 4.4 in the control. In the field trial, potato growth, root health and tuber disease levels were evaluated in plots where disease management involved either incorporation of mustard or rye cover crop roots, shoots and whole plants (roots plus shoots) or standard farmer practice of a fumigated fallow as a control. White root tissue was used as a health indicator, and averaged 58 and 78% in the fumigated control and mustard cover crop treatments, respectively. The highest healthy root tissue status (91%) was recorded where whole plants of mustard were incorporated. In contrast to the visual assessment of root and tuber health, tuber yield in the field was not influenced by cover crop treatment. Across experiments, the incorporation of or exposure to whole mustard plants was consistently effective at suppressing soil-borne fungi and promoting healthy roots and tubers, especially at higher rates of biomass. Mustard should be managed so as to maximize incorporated biomass for effective biofumigation. Multipurpose management requiring removal of mustard shoots is incompatible with promoting potato rhizosphere health.     

植物抗旱性中的补偿效应及其在农业节水中的应用

在论述植物补偿效应存在类型和研究范畴的基础上,详细评述了植物抗旱性中根系形态结构功能及地上部干物质积累、产量和水分利用效率方面的补偿效应及其影响因素,并对植物抗旱作用中补偿生长的可能生理学机制作了探讨。同时,对补偿效应在提高农业水分利用效率中的应用进行了讨论     

不同滴灌方式下棉花生物量和产量的水氮调控效应

通过3个水平的灌水量和施氮量（低、中、高）的田间试验,研究了田间不同滴灌方式下棉花生物量和产量的水氮调控效应.结果表明：在1带4行、2带4行、2带6行滴灌模式下灌水量由低（分别为90、140、140 mm）到中（分别为150、200、200 mm）时,地上部干物质量分别提高9.2%、37.9%和23.5%,籽棉产量分别提高19.1%、14.1%和16.0%;灌水量由中到高（分别为210、260、260 mm）时,地上部干物质量分别提高15.8%、19.1%和16.7%,籽棉产量分别提高7.7%、11.2%和9.5%.施氮量由低（67.6 kg·hm^-2）到中（95.2 kg·hm^-2）时,地上部干物质量2带4行模式提高14.3%,籽棉产量1带4行模式提高22.2%,其他模式无显著变化;施氮量由中到高（122.8 kg·hm^-2）时,籽棉产量3种模式分别提高7.4%、13.9%和9.9%,地上部干物质量无显著变化.与1带4行和2带6行模式相比,2带4行模式地上部干物质量和籽棉产量的水氮调控效应更明显,相同水氮处理下2带4行地上部干物质量和籽棉产量均高于2带6行和1带4行.表明2带4行是最有利于滴灌棉花田间水氮管理的模式.     

Coordinate expression of AOS genes and JA accumulation: JA is not required for initiation of closing layer in wound healing tubers

Wounding induces a series of coordinated physiological responses essential for protection and healing of the damaged tissue. Wound-induced formation of jasmonic acid (JA) is important in defense responses in leaves, but comparatively little is known about the induction of JA biosynthesis and its role(s) in tuber wound-healing. In this study, the effects of wounding on JA content, expression of JA biosynthetic genes, and the involvement of JA in the initiation of closing layer formation in potato tubers were determined. In addition, the role of abscisic acid (ABA) in wound-induced JA accumulation was examined. The basal JA content in non-wounded tuber tissues was low (<3 ng g⁻¹ FW). Two hours after wounding, the JA content increased by >5-fold, reached a maximum between 4 and 6 h after wounding, and declined to near-basal levels thereafter. Tuber age (storage duration) had little effect on the pattern of JA accumulation. The expressions of the JA biosynthetic genes (StAOS2, StAOC, and StOPR3) were greatly increased by wounding reaching a maximum 2-4 h after wounding and declining thereafter. A 1-h aqueous wash of tuber discs immediately after wounding resulted in a 94% inhibition of wound-induced JA accumulation. Neither JA treatment nor inhibition of JA accumulation affected suberin polyphenolic accumulation during closing layer development indicating that JA was not essential for the initiation of primary suberization. ABA treatment did not restore JA accumulation in washed tuber tissues suggesting that leaching of endogenous ABA was either not involved or not solely involved in this loss of JA accumulation by washing. Collectively, these results indicate that JA is not required for the induction of processes essential to the initiation of suberization during closing layer development, but do not exclude the possibility that JA may be involved in other wound related responses.     

Root zone solute dynamics under drip irrigation: A review

Infiltration and subsequent distribution of water and solutes under cropped conditions is strongly dependent on the irrigation method, soil type, crop root distribution, and uptake patterns and rates of water and solutes. This review discusses aspects of soil water and solute dynamics as affected by the irrigation and fertigation methods, in the presence of active plant uptake of water and solutes. Fertigation with poor quality water can lead to accumulation of salts in the root zone to toxic levels, potentially causing deterioration of soil hydraulic and physical properties. The high frequency of application under drip irrigation enables maintenance of salts at tolerable levels within the rooting zone. Plant roots play a major role in soil water and solute dynamics by modifying the water and solute uptake patterns in the rooting zone. Modeling of root uptake of water and solutes is commonly based on incorporating spatial root distribution and root length or density. Other models attempt to construct root architecture. Corn uptake rate and pattern of nitrate nitrogen was determined from field studies of nitrate dynamics under drip irrigation using TDR monitoring. The determined nitrate nitrogen uptake rates are within literature values for corn. This revised version was published online in June 2006 with corrections to the Cover Date.     

Hormonal changes in papaya seedlings subjected to progressive water stress and re-watering

Changes on abscisic acid (ABA), jasmonic acid (JA) and indole-3-acetic acid (IAA) levels were investigated in papaya seedlings (Carica papaya L.) cv. “Baixinho de Santa Amalia” under progressive water stress and subsequent rehydration. Also, the behaviour of leaf gas exchange and leaf growth was determined under stress condition. The results indicated that ABA and JA differ in their pattern of change under water stress. ABA continuously increased in leaves and roots during the whole period of stress whereas JA showed a sharp increase and a later decrease in both organs. Re-watering reduced rapidly (24 h) leaf and root ABA to control levels whereas the influence on JA levels could not be assessed. Drought and recovery did not alter IAA levels in leaf and root tissues of papaya seedlings. In addition, water stress reduced stomatal conductance, photosynthetic rate, transpiration rate, the percentage of attached leaves and leaf growth. Rehydration reverted in few days the effects of stress on leaf growth and gas exchange parameters. Overall, the data suggest that ABA could be involved in the induction of several progressive responses such as the induction of stomatal closure and leaf abscission to reduce papaya water loss. In addition, the pattern of accumulation of JA is compatible with a triggering signal upstream ABA. The unaltered levels of IAA could suggest a certain adaptive ability of papaya to maintain active physiological processes under progressive drought stress.