快速脱水抑制葡萄干制过程中膜脂过氧化及褐变

为探索脱水速度对无核白葡萄干制过程中膜脂过氧化作用及褐变的影响,以新疆无核白葡萄为试验材料,经过葡萄促干剂处理后,采用快速脱水和缓慢脱水2种处理,质量每减轻10%进行取样,测定脱水过程中果实干基含水率、干燥速率、褐变度、细胞膜透性、丙二醛(malonaldehyde,MDA)含量、脂氧合酶(lipoxygenase,LOX)、超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、过氧化物酶(peroxidase,POD)、多酚氧化酶(polyphenol oxidase,PPO)活性以及总酚含量的变化。结果表明:与缓慢脱水相比,快速脱水处理显著(P0.05)降低了无核白葡萄褐变度的上升,减少MDA生成量以及膜透性的增加,抑制LOX活性的升高,保持较高的活性氧清除酶SOD、CAT及POD活性及较高的总酚含量,且使PPO活性保持在一个较低的水平。因此认为,快速脱水可以有效地抑制无核白葡萄的膜脂过氧化作用对细胞膜的破坏,保持细胞的完整性,且PPO活性较低,从而减少无核白葡萄脱水褐变的发生。研究结果为快速脱水在无核白葡萄干制中的应用提供参考。     

Factors affecting taste scores of early season seedless table grape cv. Mystery and Prime.

Table grapes of cv. Mystery and Prime were harvested from 10 farms in two growing areas of Israel over two seasons. The grapes were separated on the basis of sucrose solutions from 12 to 18%; soluble solids content (SSC), titratable acidity (TA), and pH were determined; and taste tests were conducted. SSC gave the best correlation with taste tests, and multiple regression of SSC, TA, and pH improved the correlation. There were both seasonal and regional differences in the measured maturity parameters. Lower TA and higher pH were found in grapes from the Jordan Valley. Volatiles were predominantly C(6) compounds hexanal and 2-hexanal, contributing a fresh aroma to the grapes. It is concluded that Mystery and Prime grapes have good organoleptic quality if harvested at SSC levels of >14%.     

Polyphenol oxidase activity, color changes, and dehydration in table grape rachis during development and storage as affected by n-(2-chloro-4-pyridyl)-n-phenylurea

Flame Seedless grapes were sprayed with N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU) at 0, 2.5, and 5.0 ppm to develop rachis resistant to browning and dehydration. Rachis polyphenol oxidase (PPO) activity was determined during cluster development. Cluster components were weighed at commercial (CM), and physiological maturity (PM). PPO activity, rachis color changes (L and a), and cluster weight loss were evaluated at 0 degrees C for 8, 16, 32, and 56 days. CPPU-treated rachis had a decrease of 36% in PPO activity and a week delay in peak activity. At PM, dry weight of CPPU-treated rachis increased by 3 g. Postharvest rachis PPO activity declined with CPPU application, and color changes followed the same pattern for CM and PM. After 32 days of storage, L and a in lateral branches were significantly superior in CPPU treatments. Weight losses below 2.1% were significantly lowest in CPPU-treated clusters for 16 days of storage regardless of cluster maturity.     

全膜覆土穴播种植冬小麦对旱地土壤微生物数量及生物量的影响

[目的]揭示全膜覆土穴播种植方式对土壤微生态环境的影响,为其进一步推广应用提供参考依据。[方法]采用田间试验,研究不同覆膜种植方式对冬小麦各生育期土壤微生物数量和微生物量的影响。[结果]全膜覆土穴播方式可明显增加冬小麦各生育期的土壤微生物数量(除自生固氮细菌)以及微生物量C和N。与传统栽培方式相比,全膜覆土穴播方式和全膜不覆土穴播方式土壤细菌、放线菌、真菌分别平均提高32.07%和10.23%,31.27%和10.57%,44.56%和26.51%;氨化细菌和硝化细菌分别平均提高32.54%和37.80%,79.20%和107.22%;微生物量C和N含量分别平均提高29.90%,20.68%%和29.41%,18.02%。各处理土壤微生物数量和微生物量整体从小麦返青期开始升高,到拔节期或抽穗期达到峰值,生长后期有所下降。[结论]全膜穴播方式下土壤微生物数量和微生物量土壤随土层的加深呈减少的趋势。全膜覆土穴播方式有利于冬小麦土壤微生物数量和微生物量的提高。     

采前喷施脱落酸对欧李果实品质的影响

为探究采前喷施脱落酸(ABA)对欧李果实品质的影响,本研究选择农大6号和农大7号2个欧李品种为试验材料,在喷施不同浓度和不同次数的ABA后测定成熟果实的单果重、可溶性固形物含量、可滴定酸含量、类黄酮含量、总酚含量以及抗氧化能力。结果表明,喷施不同浓度和不同次数的ABA后,农大6号欧李果实可滴定酸含量、类黄酮含量、总酚含量以及抗氧化能力降低,对于可滴定酸含量而言,喷施2次比喷施1次的降酸效果明显,而类黄酮含量、总酚含量以及抗氧化能力受ABA浓度和喷施次数的变化影响不大。各处理下农大7号欧李果实的单果重和可溶性固形物含量均得到了升高,类黄酮含量、总酚含量以及抗氧化能力受ABA浓度和喷施次数的变化影响较大。根据主成分分析进行排名可知,不同浓度不同次数的脱落酸处理后农大6号欧李果实综合评分均低于对照,果实综合品质下降,农大7号欧李果实综合评分均高于对照,当脱落酸浓度为25 mg·L^-1,喷施次数为1次时对果实综合品质的提升效果最好。本研究为提升欧李果实品质选取喷施适宜浓度和次数的ABA提供了理论基础。     

缺磷胁迫对长豇豆幼苗脱落酸含量的影响

研究耐缺磷程度不同的长豇豆品种在缺磷胁迫下脱落酸(ABA)含量的变化。结果表明缺磷胁迫下长豇豆幼苗根系ABA含量都增高,缺磷前期下降后升至1个高峰后再降低,高峰出现的迟早与品种耐缺磷性有密切关系,不耐缺磷的二芦白比耐缺磷的芦花白出现早,平均升幅香港青二芦白芦花白。缺磷胁迫下长豇豆幼苗老茎叶和最嫩完全展开叶ABA含量升高,平均升幅香港青二芦白芦花白,但缺磷后期ABA含量二芦白香港青芦花白;缺磷胁迫下幼苗嫩茎叶ABA含量各品种都升高,升幅芦花白二芦白香港青。缺磷胁迫下长豇豆幼苗茎叶ABA含量的增加可能促进磷和水分的运输、减轻膜质过氧化,是对缺磷胁迫的适应机制之一。     

渗透胁迫下烤烟根和叶片中内源激素含量的变化

采用酶联吸附免疫测定(ELISA)技术分析了渗透胁迫下烤烟根和叶片中脱落酸(ABA)、生长素(IAA)、赤霉素(GA3)和异戊烯基腺嘌呤(iPA)4种内源激素含量的变化。结果表明,渗透胁迫下烤烟叶片水势降低,蛋白质含量增加,根和叶中ABA和iPA含量升高,IAA和GA3含量减少。培养液渗透势-0.5 MPa与-0.25 MPa两处理相比,前者烟叶水势和ABA含量较低,蛋白质及IAA、GA3和iPA含量较高,根中iPA和叶中ABA含量达到高峰及根中GA3含量出现低谷所需时间较短,其它指标的变化二者同步。根与叶中激素含量相比,在胁迫处理前期(6 h)根中IAA和GA3含量的降低幅度较大,ABA含量峰值出现较早,说明烤烟根中的激素对渗透胁迫的反应更加敏感。     

Ca^2＋、ABA预处理蝴蝶兰类原球茎的脱水保护系统比较及信号传导关系

CaCl2和ABA溶液及两者联合分别预处理蝴蝶兰类原球茎（PLB）后脱水,对比PLB脱水前后的成活率、脱水保护系统指标变化及Ca^2＋与ABA信号传导关系。结果表明,CaCl2和ABA溶液及两者联合预处理均能明显提高PLB脱水后的成活率。CaCl2和ABA溶液对可溶性糖、蔗糖、还原糖、SOD和总抗氧化能力有相同的效应趋势,对可溶性蛋白、热稳定蛋白含量及POD、CAT活性的作用趋势有所差异。ABA溶液提高PLB耐脱水性的能力被胞质Ca^2＋螯合剂BAPT～AM和钙调蛋白拮抗剂氯丙嗪所削弱,Ca^2＋预处理提高PLB耐脱水能力被ABA合成抑制剂环丙嘧啶醇削弱。在蝴蝶兰PLB的耐脱水性诱导中,Ca^2＋和ABA具有基本相同的生理生化基础,在信号传递中两者互相关联,CaCl2取代ABA用于提高PLB耐脱水性是可行的。     

丛枝菌根真菌对NaCl胁迫下番茄内源激素的影响

采用盆栽试验研究了不同浓度NaCl（03%、06%和10%）胁迫下,接种丛枝菌根真菌Glomus mosseae-2 对番茄内源激素的影响。结果表明：（1）盐胁迫下,植株生长受抑,生长促进物质IAA、GA3和Zeatin含量下降,生长抑制物质ABA含量增加,接种Glomus mosseae-2增加了植株干物质量和这些激素的含量;（2）菌根形成过程中,Glomus mosseae-2参与调节内源激素平衡, 降低了叶片ABA/IAA、ABA/GA3、ABA/Zeatin及ABA/ (IAA+GA3+Zeatin)的比值; （3）气孔导度（gs））和ABA/Zeatin值呈极显著负相关,同一盐浓度胁迫下,接菌株有较高gs和较低的ABA/Zeatin值。 ABA和Zeatin共同调节气孔对盐胁迫的响应,维持接菌株较高的气孔导度,增强了番茄的耐盐性。     

Relationship of ethylene biosynthesis to volatile production, related enzymes, and precursor availability in apple peel and flesh tissues

Regulation of ethylene biosynthesis or action has a major effect on volatiles production in apples. To understand the biochemical processes involved, we used Greensleeves apples from a transgenic line with a high suppression of ethylene biosynthesis. The study was focused at the level of the aroma volatile-related enzymes, including alcohol acyltransferase (AAT), alcohol dehydrogenase (ADH), and lipoxygenase (LOX) and at the level of amino acids and fatty acids as aroma volatile precursors in peel and flesh tissues. In general, volatile production, enzyme activity levels, and precursor availability were higher in the peel than the flesh and were differentially affected by ethylene regulation. AAT enzyme activity showed a clear pattern concomitant with ethylene regulation. Contrarily, ADH and LOX seem to be independent of ethylene modulation. Isoleucine, an important precursor of aroma compounds including 2-methylbutanoate esters, showed a major increase in the peel during ripening and responded significantly to ethylene regulation. Other important aroma volatiles precursors, like linoleic and linolenic acid, showed an accumulation during ripening associated with increases in aldehydes. The significance of these changes in relation to aroma volatile production is discussed.     

Impact of blanching and packaging atmosphere on the formation of aroma compounds during long-term frozen storage of leek (Allium ampeloprasum Var. Bulga) slices.

The content of aroma compounds and the catalytic activity of lipoxygenase (LOX), alliinase, hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH) were analyzed in unblanched and blanched 15-mm leek slices packed in atmospheric air (21% O2) or 100% nitrogen (0% O2) three times during 12 months of frozen storage (12 M). The total amount of sulfur compounds and the total amount of aldehydes were greatly influenced by storage time, atmosphere, and blanching [concentration of sulfur compounds in fresh unblanched (UNB) slices = 1.35 mg/L, fresh blanched (B) slices = 1.09 mg/L, UNB 21% O2 12 M = 0.656 mg/L, UNB 0% O2 12 M = 2.11 mg/L, B 21% O2 12 M = 1.14 mg/L, B 0% O2 12 M = 1.59 mg/L]. B 0% O2 was closest to the original ratio between sulfur compounds and aldehydes after 12 months. The activities of HPL and alliinase were totally lost after 12 months, and ADH showed minimal activity, whereas LOX (UNB 0% O2) showed approximately 25% of the original activity. LOX was the most and HPL the least heat labile enzyme investigated.     

Impact of blanching and packaging atmosphere on the formation of aroma compounds during long-term frozen storage of leek (Allium ampeloprasum Var. Bulga) slices.

The content of aroma compounds and the catalytic activity of lipoxygenase (LOX), alliinase, hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH) were analyzed in unblanched and blanched 15-mm leek slices packed in atmospheric air (21% O2) or 100% nitrogen (0% O2) three times during 12 months of frozen storage (12 M). The total amount of sulfur compounds and the total amount of aldehydes were greatly influenced by storage time, atmosphere, and blanching [concentration of sulfur compounds in fresh unblanched (UNB) slices = 1.35 mg/L, fresh blanched (B) slices = 1.09 mg/L, UNB 21% O2 12 M = 0.656 mg/L, UNB 0% O2 12 M = 2.11 mg/L, B 21% O2 12 M = 1.14 mg/L, B 0% O2 12 M = 1.59 mg/L]. B 0% O2 was closest to the original ratio between sulfur compounds and aldehydes after 12 months. The activities of HPL and alliinase were totally lost after 12 months, and ADH showed minimal activity, whereas LOX (UNB 0% O2) showed approximately 25% of the original activity. LOX was the most and HPL the least heat labile enzyme investigated.     

Effect of Molybdenum Foliar Sprays on Yield,Berry Size,Seed Formation,and Petiolar Nutrient Composition of “Merlot” Grapevines

Abstract

Field experiments with irrigated “Merlot” vines were carried out at 3 sites in the Mount Lofty Ranges of South Australia over 3 years to examine the effects of molybdenum (Mo) foliar sprays on bunch yield, berry size, and nutrient composition of petioles. Bunches were divided into different size grades for black and green berries. Basal petioles were sampled at flowering and veraison for nutrient analyses. In year 3, seed number per berry was assessed at sites 2 and 3. Two Mo foliar sprays (each spray contained 118 g Mo as sodium molybdate/ha in 410–800 L/ha of water) applied before flowering increased yield per vine and bunch weight in all experiments in year 2 and at site 3 in year 3. Yield responses ranged from 221% at site 1 to 750% at site 2 in year 2 and 70% for site 3, year 3. Average bunch weight increased from 243% at site 2 to 425% at site 1 for year 2 and by 69% at site 3 in year 3, and was the main yield component affected by Mo application. In year 1, the application of Mo did not affect yield or bunch weight at any site. In year 2, the application of Mo increased the yield of 5–15 mm colored berries by 301, 499, and 258% at sites 1, 2, and 3, respectively, and by 70% at site 3, year 3. Mo application increased the percent of berries, which had one or more functional seeds (when assessed at sites 2 and 3 in year 3). Molybdenum concentrations in petioles sampled at flowering and veraison increased in response to applied Mo in all years. Petiolar Mo concentrations in unsprayed vines were consistently higher in year 1 compared with other years. The effect of applied Mo on the concentration of other nutrients in basal petioles sampled at flowering and veraison were small and of little practical importance. Nitrate-N did not accumulate in the petioles of unsprayed plants in any year. Changes in petiolar Mo concentrations between flowering and veraison were dependent on supply. Nitrate-N, total-N, and phosphorus (P) concentrations declined with time, while calcium (Ca), manganese (Mn), and iron (Fe) tended to increase. At flowering, Mo concentrations in basal petioles of 0.05–0.09 mg/kg were associated with significant bunch yield response to applied Mo. Molybdenum deficiency can be a major factor in the occurrence of berry development disorders such as shot berry formation and hens and chickens (millerandage) in “Merlot” grapevines. The increased percent of colored berries with one or more functional seeds and the decrease in the proportion of green berries suggests that Mo application affected pollination and/or fertilization, and thereafter berry development.     

高温高湿胁迫对黄瓜产量形成的影响机理

以黄瓜品种‘津优101’（Jinyou101）为试材,于2020年5-9月在南京信息工程大学人工气候室开展人工环境控制实验,以探明高温高湿复合灾害对设施黄瓜产量形成的影响机理。利用温度、湿度、持续时间三因素进行正交试验设计,昼温/夜温设置32℃/22℃、35/25℃、38℃/28℃和41℃/31℃共4个水平,空气相对湿度设置50%、70%和90%共3个水平（湿度变化范围控制在±5个百分点）,持续时间设计3、6、9和12d。以昼温28℃/夜温18℃、空气相对湿度50%±5个百分点处理为对照（CK）。测定叶片光合参数、叶绿素含量、顶芽内源激素含量,观测各个节位的花性分化情况及最终产量。结果表明：（1）黄瓜叶片的叶绿素总量随着处理温度的升高和胁迫时间的延长,下降幅度逐渐加大。胁迫12d后叶片叶绿素a、叶绿素b、类胡萝卜素含量达到最低值,分别较CK下降31.51%、22.62%、37.10%;（2）黄瓜叶片的Pmax（最大净光合速率）、LSP（光饱和点）、AQE（表观量子效率）值均随着高温高湿胁迫程度的加深显著降低,41℃高温处理后黄瓜叶片的LSP、AQE、Pmax值达到最低,分别较CK降低48.78%、40.00%、43.04%,日最高温度32～41℃范围内,70%空气相对湿度处理下黄瓜叶片的Pmax值高于其它湿度处理,与CK差异较小;（3）在植株花芽分化进程中,黄瓜顶芽中的ZT（反玉米素）、ABA（脱落酸）和GA3（赤霉素）含量均呈现出先升高后降低的趋势,IAA含量则随着黄瓜植株的生长逐渐减小。黄瓜顶芽中的ZT、IAA、GA3含量均随着温度、胁迫天数的增加而逐渐降低,ABA含量呈反向变化。41℃高温处理结束当日,黄瓜顶芽中ZT、IAA、GA3含量分别较CK降低47.37%、26.38%、83.65%,ABA含量则较CK提高27.27%;胁迫12d后黄瓜顶芽中ZT、IAA、GA3含量达到同时期内的最低值,分别为0.07、1.11、0.75µg·g⁻¹,而ABA含量则达到同时期内最高值,为1.89µg·g⁻¹;（4）高温高湿胁迫提高了黄瓜各雌花产生节位,而雌花节率和雌雄花花芽数量则降低;70%空气相对湿度处理下雌花产生的节位有所降低,雌花节率和雌花花芽数量有所提高;（5）高温高湿胁迫导致黄瓜产量显著降低,41℃处理后黄瓜产量较CK降低38.50%。研究发现高温通过抑制黄瓜叶片的光合作用,扰乱顶芽中的内源激素平衡,使雌花分化数量减少,从而导致最终产量降低。     

Novel edible coating based on aloe vera gel to maintain table grape quality and safety

A novel edible coating based on Aloe vera gel obtained according to SP Patent Filed 200302937 has been used as a means of preservation to maintain the quality and safety of cv. Crimson Seedless table grapes during cold storage and subsequent shelf life. Table grapes have a crucial economic value as a dessert fruit, but once harvested show a reduction of shelf life due to a rapid loss of quality. Uncoated clusters showed a rapid deterioration with an estimated shelf life period of 7 days at 1 degrees C plus 4 days at 20 degrees C, based on the fast weight loss, color changes, accelerated softening and ripening, rachis browning, and high incidence of berry decay. On the contrary, those clusters treated with A. vera gel significantly delayed the above parameters related to postharvest quality losses, and storability could be extended up to 35 days at 1 degrees C. Interestingly, this edible coating was able to reduce the initial microbial counts for both mesophillic aerobic and yeast and molds, which significantly increased in uncoated berries over storage. Moreover, the sensory analyses revealed beneficial effects in terms of delaying rachis browning and dehydration and maintenance of the visual aspect of the berry without any detrimental effect on taste, aroma, or flavors. To the authors' knowledge, this is the first time A. vera gel has been used as an edible coating in fruits, which would be an innovative and interesting means for commercial application and an alternative to the use of postharvest chemical treatments.     

不同生育期水分胁迫对设施延后栽培葡萄土壤温度与果实品质的影响

[目的]探讨河西荒漠绿洲区(以甘肃省张掖市为代表)水分调控下土壤温度的基本变化特征以及土壤温度与果实品质之间的联系,为设施延后栽培技术研究提供理论依据。[方法]将设施延后栽培葡萄分为5个生育期,在各个生育期设1个土壤含水率下限为田间持水率(θf)的55%的中度水分调控处理(GS,VS,FS,ES,CS),开展了上述设定条件下的研究。[结果](1)随着土层深度的增加,设施延后栽培葡萄土壤温度均表现为5cm10cm15cm20cm25cm。且在葡萄全生育期内各个土层土壤温度变化规律均为先升高后降低的趋势,水分胁迫不仅提高了该生育阶段的土壤温度同时对其下一生育阶段的土壤温度也具有十分重要的作用。(2)果穗质量和单粒重均GS处理最高,可溶性固形物FS处理最高,总糖含量CS处理最多,可滴定酸含量CS最低。[结论]设施延后栽培葡萄土壤温度受环境影响明显,在白天土壤温度是由表层向深层传递,且水分胁迫具有增加土壤温度的作用。要提高葡萄甜度同时降低酸度,增加成熟度需在生育后期即果实膨大期以及着色成熟期适当程度的提高土壤温度。     

菌渣还田对梨园土壤性状及梨果品质的影响

在7年生梨树行间进行10、12.5和15kg/m23种投料量的覆土栽培平菇试验,将出菇后的菌渣还田,以探明菌渣还田对梨园土壤性状及梨果实品质的影响。结果表明:(1)与对照相比,菌渣还田使0～40cm土层土壤容重降低7.3%～14.9%(P<0.05),土壤空隙度增加4.2%～11.5%(P<0.05),土壤总有机碳含量提高32.7%～56.0%(P<0.01),活性有机碳含量提高39.2%～92.5%(P<0.01),并提高了活性有机碳占总有机碳含量比例;(2)与对照相比,0～40cm土层细菌数量提高12.1%～47.0%,放线菌数量提高19.5%～82.8%;真菌数量68.7%～163.6%(P<0.01),微生物生物量碳氮分别提高13.4%～32.2%(P<0.01)和9.3%～37.1%;(3)土壤脲酶活性提高23.2%～47.6%(P<0.05),蔗糖酶活性提高25.7%～58.6%(P<0.01),磷酸酶活性提高14.8%～33.6%(P<0.01)、过氧化氢酶活性提高4.8%～20.2%,且随菌渣还田量的增加而增加;(4)菌渣还田使梨单果重提高9.2%～15.0%(P<0.05),硬度增加3.9%～5.3%(P<0.05),可溶性固形物含量提高11.7%～19.5%(P<0.05),可溶性糖含量提高4.2%～6.3%(P<0.05),可滴定酸含量降低3.1%～7.7%。在梨树行间按15kg/m2投料量覆土栽培平菇,还田后的菌渣可显著提高梨园0～40cm土层土壤肥力,并改善梨果实品质。     

Formation of volatile compounds in model experiments with crude leek (Allium ampeloprasum Var. Lancelot) enzyme extract and linoleic acid or linolenic acid

Three continuous assays are described for lipoxygenase (LOX), hydroperoxide lyase (HPL) and alcohol dehydrogenase (ADH) in leek tissue. The catalytic activity of LOX showed significant difference (significance level 5%) between linolenic acid (9.43 x 10(-)(4) katals per kg protein) and linoleic acid (2.53 x 10(-)(4) katals per kg protein), and the pH-optimum of LOX was 4.5-5.5 against linoleic acid. The catalytic activity of HPL was statistically the same for 9-(S)-hydroperoxy-(10E,12Z)-octadecadienoic acid (1.01 x 10(-)(2) katals per kg protein) and 13-(S)-hydroperoxy-(9Z,11E)-octadecadienoic acid (7.69 x 10(-)(3) katals per kg protein). ADH showed a catalytic activity of 5.01 x 10(-)(4) katals/kg of protein toward hexanal. Model experiments with crude enzyme extract from leek mixed with linoleic acid or linolenic acid demonstrated differences in the amount of produced aroma compounds. Linoleic acid resulted in significantly most hexanal, heptanal, (E)-2-heptenal, (E)-2-octenal, (E,E)-2,4-decadienal, pentanol, and hexanol, whereas linolenic acid resulted in significantly most (E)-2-pentenal, (E)-2-hexenal, (E,Z)-2,4-heptadienal, (E,E)-2,4-heptadienal, and butanol. Leek LOX produced only the 13-hydroperoxide of linoleic acid and linolenic acid.     

CHANGES IN ENDOGENOUS HORMONAL STATUS IN CORN (ZEA MAYS) HYBRIDS UNDER DROUGHT STRESS

Corn has several mechanisms that allow it to perceive the incoming water deficit and rapidly regulate its growth and physiology to cope with this stress. Among these regulated physiological responses, phytohormones, such as abscisic acid (ABA), gibberellin (GA₃), indole acetic acid (IAA), and zeatin (ZT) have important roles. To evaluate changes in hormonal status of corn hybrids under different drought stress levels, a greenhouse study was conducted at the College of Agriculture, Shiraz University, Iran, during summer 2010. Treatments consisted of drought stress in five levels: 100% field capacity (F.C.) as control, 80, 60, 40, and 20% F.C. and three corn hybrids, including single cross 704 (SC704), Maxima, and double cross 370 (DC370). Results showed that drought stress significantly affected phytohormones concentration, ABA concentration was increased and GA₃, IAA and ZT concentrations were decreased. Indeed, there was an initial increase (about 13.5% more than control) in IAA concentration. In severe drought condition, ABA concentration was eventually decreased (37.8% less than the first drought level, i.e., 80% F.C.). The ratios of GA₃, IAA and ZT to ABA concentration were also decreased. Among hybrids, SC704 showed the highest phytohormone concentrations and DC370 had the highest ratios of GA₃, IAA, and ZT to ABA concentrations. Overall, the results of this study suggest that although mild drought stress was associated with greater ABA concentration, it had negative impact on GA₃, IAA, and ZT concentrations. Furthermore, SC704 hybrid appeared to be more resistant to drought stress than the other hybrids.