Impacts of water stress on gas exchange,water relations,chlorophyll content and leaf structure in the two main Tunisian olive (Olea europaea L.) cultivars

Leaf structural adaptations for the reduction of water loss were examined in two olive (Olea europaea L.) cultivars (Chemlali and Chétoui) growing under water stress conditions. Leaf measurements included leaf tissue thickness, stomatal density, trichome density, specific leaf area, leaf density, water relations, and gas exchange. We found considerable genotypic differences between the two cultivars. Chemlali exhibited more tolerance to water stress, with a thicker palisade parenchyma, and a higher stomatal and trichome density. Chemlali leaves also revealed lower specific leaf area and had higher density of foliar tissue and lower reduction in net CO₂ assimilation rate. The mechanisms employed by these two cultivars to cope with water deficit are discussed at the morpho-structural level. The morphological and structural characteristics of the leaves are in accordance with physiological observations and contribute to the interpretation of why the olive cv. Chemlali is more drought-tolerant than cv. Chetoui. Furthermore, from the behaviour of Chemlali plants we consider this cultivar very promising for cultivation in semi-arid areas.     

Relationship between ADH activity,ripeness and softness in six tomato cultivars

Fruit from six tomato cultivars were harvested at progressive stages of ripeness. Fruit softness was measured together with the activity of the alcohol dehydrogenase (ADH) enzyme in the pericarp tissue. The rate of increase in ADH activity in the ripening fruit was found to be strongly correlated (r=0.970) with the rate of softening of the fruit suggesting that induction of ADH activity in the fruit was possibly a function of the softening of the fruit rather than a direct function of ripening. As the ADH enzyme is involved in several aspects of flavour development in the ripening tomato fruit, in particular the regulation of accumulation of some aldehydes and alcohols, a correlation between fruit softening and activity of the enzyme has important implications regarding flavour development in tomato fruit of firm or soft varieties.     

水分胁迫下外源NO对核桃叶绿素荧光的影响

探讨了外源NO对水分胁迫下核桃叶片荧光参数的影响。结果表明,水分胁迫下,核桃叶片的荧光参数最大光化学量子效率(Fv/Fm)、PSⅡ反应中心的实际光化学效率(φPSⅡ)、光化学猝灭系数(qP)、非光化学猝灭系数(NPQ)均降低,经NO供体硝普钠(SNP)诱导处理后,荧光参数下降程度减小,且随着SNP处理浓度增大,缓解作用愈明显。表明外源NO处理一方面提高了光能转换效率和PSⅡ的潜在活性,另一方面增强了过剩光能的非化学耗散,有利于保护光合机构免受环境胁迫的伤害。     

Concurrent action of salinity and water stress on leaf gas exchange and water relations in tomato

Tomato plants (Lycopersicon esculentum Mill.) grown in pots were irrigated for four weeks with 0.04,0.08,0.12 molai NaCl solutions and a control solution. Half the plants in each salt treatment were water stressed for five days. Single leaf gas exchange at near ambient C02, water consumption and plant water relations were measured. Both salt and water stress reduced growth, water potential and gas exchange rates. Well watered plants were only slightly stressed by a salt concentration of 0.04 molai, while plant growth continued at a concentration of 0.08 molai. Short-term water stress imposed greater stress than long-term salt stress; carbon exchange rate (CER) was partially limited by stomatal closure in the case of water stress and by mesophyll limitation with longer-term salinity treatments. Osmoregulation in response to salt stress did not impart particular tolerance to transient water stress.     

Effects of shading on gas exchange,specific leaf weight and chlorophyll content in four kiwifruit cultivars under field conditions

Diurnal changes of incident photosynthetic photon flux density (PPFD), transpiration rate (E), photosynthetic rate (Pn), stomatal conductance (Cs) and water use efficiency (WUE), together with a number of environmental factors, were measured on individual leaves at well exposed and shaded positions within the canopy for four cultivars of kiwifruit (Actinidia sinensis, P.). Pn and E rates were'much lower in the shaded leaves for all cultivars due to extremely low PPFD values reaching these leaves. Cs followed a trend similar to that for Pn. Exposed leaves showed a significantly higher WUE in the morning, while no difference was observed between exposed and shaded leaves around midday. Specific leaf weight (SLW) was lower in shaded leaves, which had a greater chlorophyll content than exposed leaves.     

低温胁迫对甜瓜幼苗光合能力及叶绿素荧光参数的影响

为评价低温胁迫对甜瓜幼苗光合作用的影响,对4份甜瓜种质低温胁迫下光合速率及叶绿素荧光参数的变化进行了研究。结果表明,低温胁迫导致甜瓜叶片叶绿素含量、净光合速率(P_n)显著下降,F_v/F_m、PI_(abs)、φE_0、F_v/F_0明显降低,ABS/RC、TRo/RC、DIo/RC明显增加,说明低温胁迫严重影响甜瓜的光合性能和光合活性,其中PI_(abs)比F_v/F_m对低温响应更为敏感,可以作为甜瓜耐冷性的参考指标。     

Effect of brassinosteroids on drought resistance and abscisic acid concentration in tomato under water stress

The effect of brassinosteroid (BR) on relative water content (RWC), stomatal conductance (g_s), net photosynthetic rate (PN), intercellular CO₂ concentration (Ci), lipid peroxidation level, activities of antioxidant enzymes and abscisic acid concentration (ABA) in tomato (Lycopersicon esculentum) seedlings under water stress was investigated. Two tomato genotypes, Mill. cv. Ailsa Craig (AC) and its ABA-deficient mutant notabilis (not), were used. Water stress was achieved by withholding water and both the AC and not plants were treated with 1 μM 24-epibrassinolide (EBR) or distilled water as a control. The RWC, g_s, Ci and PN were significantly decreased under water stress. However, EBR treatment significantly alleviated water stress and increased the RWC and PN. EBR application also markedly increased the activities of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) while it decreased g_s, Ci and the contents of H₂O₂ and malondialdehyde (MDA). Interestingly, ABA concentration in AC and not plants was markedly elevated after EBR treatment although the increasing rate and amplitude of ABA in not plants treated by EBR was significantly lower than those in AC plants. Our study suggested that amelioration of the drought stress of tomato seedlings may be caused by EBR-induced elevation of endogenous ABA concentration and/or the activities of antioxidant enzymes.     

Effects of salinity on nitrate,total nitrogen,soluble protein and free amino add levels in tomato plants

The effects of salinity on nitrogen compounds were studied in three tomato (L. esc- ulentum Mill.) genotypes of different salt tolerance. The plants were grown under controlled conditions, and the salt treatments (0, 70 and 140 raM NaCl) were applied for three (Harvest 1) and ten (Harvest 2) weeks. The effects of salinity on total N and particularly N03 concentrations depended partly on the NaCl level and duration of the stress, but mainly on the different degrees of salt tolerance of the genotypes. In Harvest 1, the most tolerant genotype (GC-72) showed the highest N03 increase in the roots and no decreases in stem and leaf with increasing salinity; the intermediate-tolerant genotype (P-73) showed a similar response to that of GC-72 only at 70 mM NaCl. However, the most sensitive genotype (Volgogradskij) showed the greatest reductions in stem and leaf N03 concentrations with salinity. With longer durations of stress the different responses between the more tolerant genotypes were less evident; only Volgogradskij continued to show the highest decreases in stem and leaf N03 concentrations. A restriction of N03 transport from the root to the shoot was noted in the plants of the more tolerant genotypes treated for three weeks. This capacity for retention disappeared when the salinity induced reductions in the total N03 contents in the plants, as in the harvest 2. There was an inverse relation between N03 and Cl accumulations in shoots of all genotypes and its slope decreased with the salt sensitivity of the genotype. There was no relation between the leaf protein content and the salt tolerance of the tomato genotypes. In Harvest 1, a higher accumulation of amino acids, especially proline, was found in the leaves of the more tolerant genotypes at 140 mM NaCl. However, in Harvest 2, a similar accumulation of leaf proline was found in all genotypes, independent of their salt tolerances, and the other amino acid contents remained similar or else decreased with salinity.     

Zinc influence and salt stress on photosynthesis,water relations,and carbonic anhydrase activity in pistachio

A greenhouse study was conducted to evaluate the ameliorative effects of zinc (0, 5, 10 and 20 mg Zn kg⁻¹ soil) under saline (800, 1600, 2400 and 3200 mg NaCl kg⁻¹ soil) conditions on pistachio (Pistacia vera L. cv. Badami) seedlings’ photosynthetic parameters, carbonic anhydrase activity, protein and chlorophyll contents, and water relations. Zn deficiency resulted in a reduction of net photosynthetic rate and stomatal conductance. The quantum yield of photosystem II was reduced at zinc deficiency and salt stress. Zinc improved plant growth under salt-affected soil conditions. Increasing salinity in soil under Zn-deficient conditions, generally decreased carbonic anhydrase activity, protein, chlorophyll a and b contents. However, these adverse effects of salinity alleviated by increasing Zn levels up to 10 mg kg⁻¹ soil. Under increasing salinity, chlorophyll a/b ratio significantly increased. Zinc treatment influenced the relationship between relative water content and stomatal conductance, and between leaf water potential and stomatal conductance. It concluded that Zn may act as a scavenger of ROS for mitigating the injury on biomembranes under salt stress. Adequate Zn also prevents uptake and accumulation of Na in shoot, by increasing membrane integrity of root cells.     

Effects of watering on the yield,quality and composition of tomatoes grown in bags of peat

Two crops of tomatoes, grown in bags of peat, were supplied with 60,80,100 and 120% of the water requirement estimated from solar radiation integrals for 12 weeks after planting. Restricting water to 60% and 80% of the requirement controlled vegetative vigour but reduced final yield by about 20% and 4% respectively. These decreases were mainly because of a reduction in fruit size rather than number. Overwatering had little effect on yield but caused Mn deficiency. As restricted watering reduced the water content of the fruit, so.the dry matter, sugar, acid and potassium concentrations in the fresh material increased; this was particularly marked in plots receiving only 60% of the water requirement. The response to the treatments disappeared 4-5 weeks after they were discontinued. Retention of six extra leaves in one crop had no effect on yield. The data suggest that watering should be restricted to 80% or less of the estimated requirement in order to achieve a significant improvement in the flavour components of the fruit.     

Seismic stress effects on reproductive structures of tomato, potato, and marigold

Periodic seismic (shaking) stress influenced the growth of sexual and asexual reproductive structures of three cultivated species. It delayed anthesis of Lycopersicon esculentum Mill. 'Patio' but not of Tagetes erecta L. 'Jubilee' or Solanum tuberosum L. 'Kennebec'. Shaken 'Jubilee' marigold plants produced the same number of flowers as undisturbed plants, but flowers of shaken plants were smaller. In contrast, seismic-stressed 'Patio' tomato produced fewer buds and flowers, but fruit set was enhanced relative to that of controls. Seismic stress also reduced tuber weight of 'Kennebec' potato, whereas tuber number was unaffected. The overall effect of seismic stress was to reduce the growth of reproductive structures and, in some cases, the number of reproductive structures that developed.     

Differential flood stress resistance of two almond cultivar* based on survival,growth and water relations as stress indicators

SUMMARY

Potted almond trees (Amygdalus communis L.) of the two cvs Ramillete and Garrigues were submitted to two treatments: non-flooded (control) and flooded for 7 d in June 1991 under field conditions. After being submerged for one week, the almond trees were removed from the water (recovery period). The effects of flooding on the growth, stomatal behaviour, leaf water potential, osmotic potential and turgor potential were examined through the experimental period. Flooding caused a reduction in root dry weight of 'Ramillete', wilting, chlorosis and necrosis of the leaves, and plant death. Epinasty occurred in treated trees, but it appeared sooner in 'Garrigues' than in 'Ramillete'. Garrigues presented the lower resistance of plant plus soil (R(p+S)) for both treatments. After the flooding period, a progressive reduction of R(p+S) values was noted in 'Garrigues'. The decrease in leaf water potential by flooding in both cultivars can be related to an increase in the resistance to water uptake. Leaf osmotic and turgor potential behaviour confirm the progressive dehydration of leaf tissues. The continous decrease in v|/" \ys and values in 'Ramillete' indicated that the severity of the damage induced by flooding stress was irreversible in this cultivar. The reduction in leaf conductance (g,) can be related to the leaf water deficit by effects of flooding, the recovery of g, for 'Garrigues' occurred 20 d after leaf water potential. The differences between the cultivars suggest that they differ in their ability to withstand flood conditions and their association is not desirable in poorly drained soils.     

喷施磷酸二氢钾对桃叶片和果实性状的影响

以不同成熟期的桃品种豫甜、豫香、秋甜、秋蜜红为试材,研究了喷施磷酸二氢钾对其叶片叶绿素含量、干鲜质量比及果实的可溶性固形物含量、可溶性糖含量、可滴定酸含量、维生素C含量等品质特性的影响。结果表明,喷施磷酸二氢钾能提高叶片中叶绿素含量、干鲜质量比和果实可溶性固形物含量、可溶性糖含量;对果实的可滴定酸含量、维生素C含量影响不明显;叶片喷施不同浓度和次数的磷酸二氢钾均可推迟桃果实成熟期;喷施清水和对照处理间叶片性状和果实品质差异不明显;喷施磷酸二氢钾浓度和次数以500mg/L3次效果最显著,以300mg/L3次最经济有效。     

Utilization of correlation network analysis to identify differences in sensory attributes and organoleptic compositions of tomato cultivars grown under salt stress

In tomato production, salt stress is applied to improve the fruit quality. The change in sensory attributes and organoleptic compositions in salt-stressed tomato fruits have been extensively studied; however, little is known about their interaction with each other. Correlation network analysis provides a visual representation of biological systems and useful knowledge for metabolic data analysis of tomato fruits. The aim of this study is to identify the cultivar differences in sensory attributes and organoleptic compositions of tomato fruits grown under salt stress and to elucidate their interaction among different cultivars using correlation network analysis. Salt stress was applied by adding 100 mM NaCl to the nutrient solution. Fruits were harvested at red-ripe stage and used for the evaluation of sensory attributes such as sweetness, sourness, umami, and tomato like, and organoleptic compositions such as sugar, organic acid, amino acid, and sodium ion contents. Almost all of the sensory attributes and organoleptic compositions of the fruit were significantly high in salt-stressed cultivars compared to non-stressed cultivars, and significant differences were also observed among cultivars. The correlation network analysis of the control fruit showed that compared to other traits, sugar is one of the key traits for improvement of tomato fruit quality based on high connectivity and betweenness centrality. In contrast, a high degree of positive connectivity was not observed between organoleptic compositions and sensory attributes in the salt-stressed fruit network. These results indicate that the relationship between sensory attributes and organoleptic compositions in fruits were different between the control and salt-stressed cultivars, suggesting that the salt-stressed fruit may have a different circuit of relationship compared to control. Furthermore, based on the increase ratio (salt stress/control) network results, we suggest that the increased sugar, organic acid, and amino acid contents may have contributed to the salt stress-induced enhancement of sensory attributes.     

NaCl胁迫对葡萄幼苗叶片有机渗透调节物质和膜脂过氧化的影响

为阐明有机渗透调节物质在葡萄种质耐盐机理中的作用,以耐盐葡萄砧木抗砧5号(Vitis berlandieri-V.ri-paria×V.amurensis-V.vinifera)和盐敏感砧木Macadams(V.riparia)为试材,比较研究了在不同质量分数NaCl胁迫下,叶片膜透性、丙二醛(MDA)含量和有机渗透物质含量的变化。结果表明,盐胁迫引起葡萄叶片膜透性增加,盐敏感品种Macadams的膜透性高于耐盐砧木抗砧5号;MDA含量随盐胁迫加重而升高,但抗砧5号低于Macadams;盐胁迫下葡萄叶片中游离脯氨酸和可溶性糖含量显著上升;可溶性蛋白的变化趋势不一致。由此说明脯氨酸、可溶性糖是葡萄在盐胁迫初期的重要有机渗透调节物质,而可溶性蛋白在葡萄中的渗透调节作用还需要进一步研究。     

Effect of arbuscular mycorrhizal fungi on growth,mineral nutrition,antioxidant enzymes activity and fruit yield of tomato grown under salinity stress

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by arbuscular mycorrhizal fungi Glomus mosseae. Tomato (Lycopersicon esculentum L. cv. Zhongzha105) plants were cultivated in soil with 0, 50 and 100 mM NaCl. Mycorrhization alleviated salt induced reduction of root colonization, growth, leaf area, chlorophyll content, fruit fresh weight and fruit yield. The concentrations of P and K were higher in AM compared with nonAM plants grown under nonsaline and saline conditions. Na concentration was lower in AM than nonAM plants grown under nonsaline and saline conditions. AMF colonization was accompanied by an enhancement of activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in leaves of both salt-affected and control plants. In addition, inoculation with AMF caused reduction in MDA content in comparison to salinized plants, indicating lower oxidative damage in the colonized plants.     

Effects of auxin application on fruit formation in tomato growing under stress temperatures in the field

Summary

Tomato (Lycopersicon esculentum L. Mill) cultivars Early Urbana and Red Clode were grown in the field at adverse temperatures (stress regimes) until they set fruit in two growing seasons (Autumn and Spring) during 1999 and 2000 in Ahwaz (Southern Iran). To test the effectiveness of auxins in enhancing fruit set, racemes of tomato were sprayed during early fruit set with 25, 50 and 100 mg l^–1 4-chlorophenoxy acetic acid (4-CPA) and indole-3-butyric acid (IBA) followed by two additional applications at three intervals. The control plants were treated with deionized water. At harvest, racemes from autumn and spring plantings that were treated with 4-CPA had more large fruits than the control racemes. In both growing seasons, neither cultivar showed a significant difference in fruit set in plants treated with IBA, compared with controls. The ratio of fruit/flower in all racemes treated with 4-CPA increased significantly compared with the other treatments. However, auxin treatments did not significantly affect the number of flowers per raceme. Plants treated with 4-CPA produced the highest yield of marketable fruit. The greatest increase in total yield and parthenocarpic fruit occurred with 4-CPA treatments. Also, there was little difference between concentrations of 4-CPA on fruit set in both cultivars. It may be concluded that the response of fruit setting in tomato to either low or high temperatures regimes was auxin dependent and that 4-CPA was more effective than IBA.     

Phytochemical composition and antioxidant activity of high-lycopene tomato (Solanum lycopersicum L.) cultivars grown in Southern Italy

In this study, the antioxidant components and of six high-lycopene (Lyco 1, Lyco 2, HLY 02, HLY 13, HLY 18 and Kalvert) and one ordinary (Donald) tomato cultivars (cvs) grown simultaneously in an open-field of the Southern Italy were investigated. Lycopene, β-carotene, lutein, total phenols, flavonoids, ascorbic acid (AsA), dehydroascorbic acid (DHA) and total vitamin C (AsA + DHA) contents, as well as hydrophilic and lipophilic antioxidant activities (HAA and LAA) were determined. Significant differences were detected among tomato cvs in all studied antioxidant components, as well as in the antioxidant activity of their hydrophilic and lipophilic fractions. High-lycopene tomato cvs showed higher lycopene, β-carotene, HAA and LAA when compared to cv Donald. Cv HLY 18 showed the highest lycopene and β-carotene content with 232.9 mg/kg fresh weight (fw) and 19.4 mg/kg fw, respectively. Except for Kalvert, high-lycopene tomato cvs also obtained higher total vitamin C levels, with cv HLY 13 top ranking with an average of 352.8 mg/kg fw. LAA ranged from 133.5 μM Trolox/100 g fw in cv Donald to 540.1 μM Trolox/100 g fw in cv Lyco 2 and was significantly correlated to lycopene (r = 0.53; p < 0.01) and β-carotene (r = 0.56; p < 0.01) contents. A variation between 2.7- and 4.0-fold was found in LAA of high-lycopene tomato cvs compared to Donald. HAA was significantly correlated to the amount of DHA (r = 0.61; p < 0.01) and total vitamin C (r = 0.60; p < 0.01). Although these data require confirmation over a longer period of time, this investigation suggests a promising use of the high-lycopene tomato cvs for the production of tomatoes with higher nutritional quality.     

Effects of progesterone on water,sodium, potassium and calcium contents in striatum of rats with focal cerebral ischemia/reperfusion

AIM: To explore the neuroprotective action of progesterone(PROG), which has been proved to be a "neuroactive steroid". METHODS: The model of focal cerebral ischemia was established in rats by reverserble inserting a nylon thread with a diameter of 0.2 mm into the anterior cerebral artery through the internal carotid artery. The effect of PROG was assessed by determining water,sodium, potassium, and calcium contents in striatum of rats subjected to 2 h ischemia followed by 22 h reperfusion. RESULTS: The water,sodium,and calcium contents of middle cerebral artery occlusion(MCAO) striatum were obviously higher,the potassium content was obviously lower than those of non-MCAO striatum in I/R and DMSO groups,but there was no significant difference between these two groups.Compared with the result in I/R and DMSO groups , water, sodium and calcium contents significantly decreased, but potassium(P＜0.01) obviously elevated in MCAO striatum in the PROG-pretreated group and PROG-pre or posttreated group.There was also significant reduction in water and sodium, but not significantly changed in calcium and potassium in PROG-posttreated group. The water,sodium,potassium,and calcium contents of MCAO striatum in each PROG-treated group were not remarkably different in comparision with those in dexamethasone treatment group(P＞0.05). CONCLUSION: Treatment with PROG can significantly reduce the striatal injury of rats with cerebral ischmia-reperfusion.     

Effects of deficit irrigation on biomass,yield, water productivity and fruit quality of processing tomato under semi-arid Mediterranean climate conditions

Processing tomato is a high water demanding crop, thus requiring irrigation throughout growing season in arid and semiarid areas. The application of deficit irrigation (DI) strategies to this crop may greatly contribute to save irrigation water. A two-year study was carried out in order to assess the effects of DI upon water productivity, final biomass, fruit yield and some quality traits of open-field processing tomato cv. Brigade in a typical semi-arid Mediterranean environment of South Italy. Four irrigation treatments were studied: no irrigation following plant establishment (V0); 100% (V100) or 50% (V50) evapotranspiration (ETc) restoration up to fruit maturity, 100% ETc restoration up to flowering, then 50% ETc restoration (V100-50). Total dry biomass accumulation was significantly depressed by early soil water deficit in V0; irrigation at a reduced rate (50% ETc) from initial stages (V50) or from flowering onwards (V100-50) did not induce any losses in final dry biomass. The marketable yield did not significantly differ among plots irrigated, but an averaged irrigation water saving of 30.4% in V100-50 and 46.2% in V50 was allowed as compared to V100. Marketable yield was negatively affected by the early water shortage in V0, due to the high fruit losses (>44%). The effects of DI on fruit quality were generally the converse of those on fruit yield. DI improved total soluble solids content, titratable acidity and vitamin C content. Water use efficiency was positively affected by DI, suggesting that the crop does not benefits from the water when this last is supplied to fulfil total crop requirements for the whole season. Yield response factor, which indicates the level of tolerance of a crop to water stress, was 0.49 for total dry biomass (Kss) and 0.76 for marketable yield (Ky), indicating that in both cases the reduction in crop productivity is proportionally less than the relative ET deficit. In conclusion, the adoption of DI strategies where a 50% reduction of ETc restored is applied for the whole growing season or part of it could be suggested in processing tomato, to save water improving its use efficiency, minimizing fruit losses and maintaining high fruit quality levels. This aspect is quite important in semi-arid environments, where water scarcity is an increasing concern and water costs are continuously rising.