重水分胁迫下苹果树茎、叶水势的变化

对田间生长的3年生苹果树(红富士/M26/八棱海棠)在土壤干旱和湿润条件下的茎及叶片水势、气孔导度和净光合的日变化进行了测定。茎水势的测定采用外围新梢的直接取样测定法,以便同剪口处叶片的水势进行比较。测定结果表明,干旱土壤条件下的叶片水势稍低于土壤湿润的树,一般仅相差0.3MPa。而二个处理之间午间茎水势的差别则高达1～1.2MPa,表现出该指标对土壤干旱十分敏感。干旱条件下叶片气孔导度和净光合与土壤湿润的树也有明显差异。研究还发现,在水分严重亏缺条件下存在茎水势低于叶水势及一定压力下枝条木质部漏气现象。对这些现象的发生条件和可能原因进行了讨论。     

外源水杨酸(SA)与甜菜碱(GB)对干旱胁迫下辣椒开花结果期光合特性的影响

以“云椒2号”为试材,采用盆栽控水法,研究外源水杨酸(SA,200mg·L^-1)和甜菜碱(GB,100mmol·L^-1)对干旱胁迫下辣椒开花结果期光合生理特性的影响。结果表明:在干旱胁迫下,外源GB、SA处理的辣椒叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)有明显增高,各处理的日平均净光合速率值为GB>SA>干旱。通过相关分析得出净光合速率与环境影响因子的关系,干旱胁迫下,净光合速率与气孔导度呈正相关,而外源GB、SA处理的净光合速率与气孔导度、蒸腾作用呈正相关。     

土壤干旱胁迫下苹果叶片膨压维持对光合速率及生长的影响

以新红星和红富士苹果叶片为试材,利用P－V分析技术研究了在水分胁迫条件下叶片细胞的膨压维持方式以及细胞膨压维持对苹果叶片的光合速率、叶面积及干物质积累（叶片干重）等生理特性的效应。结果表明,两品种叶片在不同水分胁迫条件下细胞膨压维持能力不同,中度水分胁迫下膨压维持是以渗透调节和弹性调节并存,具有膨压维持能力,严重水分胁迫下渗透调节和弹性调节均消失,膨压维持能力丧失。细胞膨压的维持能够减少叶片叶绿素的破坏,维持干旱条件下（中度水分胁迫）的光合作用较正常进行,叶片正常生长及干物质积累。     

Daily and seasonal variation of water relationship in sugar apple (Annona squamosa L.) under different irrigation regimes at semi-arid Brazil

In the northeast of Brazil the drought period determines the yield period of the sugar apple (Annona squamosa L.). As a result, the use of irrigation is essential to stagger production over the course of the year. The results shown here represent an analysis of water status levels in sugar apples in daylight and seasonal periods in semi-arid regions. Two plant groups were studied: one without irrigation and the other with irrigation during drought months. This study showed that younger leaves displayed greater stomatal conductance and transpiration. In drought months, even in irrigated plants, the high air moisture deficit had a strong influence on the stomatal closure, which did not translate into a reduction in transpiration. Over the same period, the leaf water potential was −1.8 and −2.9 MPa at mid-day in irrigated and non-irrigated plants, respectively, and only the irrigated plants could recover their leaf hydration level at night. With a water deficit, plants showed greater control of transpiration through stomatal closure, with a linear relationship between stomatal conductance and transpiration.     

Citrus rootstock responses to water stress

Tolerance to drought-stress (DS) of the citrus rootstock Forner–Alcaide no. 5 (FA-5) was tested and compared with that of its parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Nine-month-old seedlings of CM, PT and FA-5 and 15-month-old grafted trees of ‘Valencia’ orange scions on these three rootstocks were cultivated in sand under glasshouse conditions and irrigated with a nutrient solution. Plants were drought-stressed by withholding irrigation until leaves were fully wilted. Survival time of both seedlings and grafted trees under DS was linked to the water extraction rate from the soil, which depended mainly on leaf biomass and on transpiration rate. Seedling responses to DS affecting leaf water relationships and gas exchange parameters varied among genotypes. FA-5 seedlings survived longer than the other seedlings, maintaining the highest levels of water potential, stomatal conductance, transpiration rate and net CO₂ assimilation towards the end of the experiment, when water stress was most severe. Thus, FA-5 was more resistant to DS than its parents (CM and PT). Moreover, rootstock affected the performance of grafted trees under water stress conditions. The higher drought tolerance induced by FA-5 rootstock could be related to the greater osmotic adjustment (OA), which was reflected by smaller reductions in leaf relative water content (RWC) and in higher turgor potentials and leaf gas exchange than the other rootstocks.     

Transpiration,photosynthetic responses,tissue water relations and dry mass partitioning in Callistemon plants during drought conditions

Callistemon is an Australian species used as ornamental plant in Mediterranean regions. The objective of this research was to analyse the ability of Callistemon to overcome water deficit in terms of adjusting its physiology and morphology. Potted Callistemon laevis Anon plants were grown in controlled environment and subjected to drought stress by reducing irrigation water by 40% compared to the control (irrigated to container capacity). The drought stress produced the smallest plants throughout the experiment. After three months of drought, the leaf area, number of leaves and root volume decreased, while root/shoot ratio and root density increased. The higher root hydraulic resistance in stressed plants caused decreases in leaf and stem water potentials resulting in lower stomatal conductance and indicating that water flow through the roots is a factor that strongly influences shoot water relations. The water stress affected transpiration (63% reduction compared with the control). The consistent decrease in g_s suggested an adaptative efficient stomatal control of transpiration by this species, resulting in a higher intrinsic water use efficiency (P_n/g_s) in drought conditions, increasing as the experimental time progressed. This was accompanied by an improvement in water use efficiency of production to maintain the leaf water status. In addition, water stress induced an active osmotic adjustment and led to decreases in leaf tissue elasticity in order to maintain turgor. Therefore, the water deficit produced changes in plant water relations, gas exchange and growth in an adaptation process which could promote the faster establishment of this species in gardens or landscaping projects in Mediterranean conditions.     

红星苹果矮化自根砧的营养耐旱生理特性

对嫁接在M7、M9、山定子砧木上的红星苹果的叶片解剖结构、叶绿素含量、净光合效率、矿质营养及耐旱性进行测定,结果表明,供试砧木对嫁接品种的叶片厚度、栅状组织厚度、比叶重、叶绿素含量、叶绿素a含量及净光合效率均无显著影响;叶片矿质元素含量,除M9、山定子与M7的B元素外,各砧木嫁接品种的N、P、K、Ca、Mg、Fe、Zn、Mn元素含量均无显著差异:在干旱条件下,山定子比M7、M9砧木耐旱,山定子与M7、M9对嫁接品种蒸腾强度无显著影响,但前者比后者叶片水势大,表现了耐旱的特性。     

Response to drought and salt stress of lemon ‘Fino 49’ under field conditions: Water relations,osmotic adjustment and gas exchange

Drought and salinity are two of the most important factors limiting the lemon yield in south-eastern Spain. The effects of drought and salt stress, applied independently, on water relations, osmotic adjustment and gas exchange in the highest evapotranspiration period were studied to compare the tolerance and adaptive mechanisms of 13-year-old ‘Fino 49’ lemon trees, in immature and mature leaves. The study was carried out in an experimental orchard located in Torre Pacheco (Murcia). Three treatments were applied: Control, well-irrigated; drought-stress (DS), non-irrigated from 15th May to 7th July and salinity, irrigated with 30 mM NaCl from 1st March to 7th July. At the end of the experiment, only DS trees showed a decreased leaf stem water potential (Ψ_md). Under DS conditions, both types of leaf lost turgor and did not show any osmotic or elastic mechanism to maintain leaf turgor. Osmotic adjustment was the main tolerance mechanism for maintenance of turgor under salt stress, and was achieved by the uptake of Cl⁻ ions. Gas-exchange parameters were reduced by DS but not by salinity, stomatal closure being the main adaptive mechanism for avoidance of water loss and maintenance of leaf turgor. Salinity gave rise to greater Cl⁻ accumulation in mature than in immature leaves. The increase of proline in immature leaves due to DS indicates greater damage than in mature leaves.     

苹果幼苗部分根系水分胁迫对光合作用主要参数的影响

以1年生苹果组培苗为试材,用改良的Hoagland营养液加20%PEG-6000进行半根渗透胁迫(HS)处理,与仅加营养液的正常水分条件的对照(CK)和加20%PEG-6000进行全根胁迫处理(TS)进行比较,研究了根系不均匀供水条件下植株的叶片水势和光合作用主要参数的反应特点。结果表明,HS与CK之间叶片的日出前水势不存在显著差异,且显著高于TS,但日水势变化动态在大部分情况下HS显著低于CK;和CK相比较,HS处理的叶片气孔导度、蒸腾速率和净光合效率显著降低,但在处理的早期显著高于TS。HS还导致叶片温度较对照显著增高。另外,试验体系中HS处理部分根系处于水分胁迫状态,而另外的根系处于良好的水分供应条件下,可用于模拟定位灌溉和分根区交替灌溉根系不均匀供水条件,对于开展相关果树生理反应及生长发育调控机制的研究提供了良好的试验体系。     

Effects of water deficit on olive trees cv. Chemlali under field conditions in arid region in Tunisia

Water scarcity in the Mediterranean basin in addition to the extension of irrigated lands is one of the main factors limiting agricultural development. The need for supplementary irrigation of the Chemlali olive cultivar (Olea europaea L.) during summer and autumn periods was investigated. Leaf water content, gas exchange parameters, fruit development and yield in rain-fed and in irrigated plants have been monitored in 12-year-old olive trees grown under environmental conditions in semi arid regions characterized by high temperatures and high light intensity. Trees were subjected to three irrigation treatments, T0, T1 and T2 corresponding respectively to 0, 33 and 66% of crop evapotranspiration (ET_c) by a drip irrigation system. The water deficit during the summer (from June to August) led to the decrease of soil moisture, leaf water content and gas exchange parameters. Irrigated trees showed the same slow activity in the three summer months as the rain-fed trees. For all treatments, net CO₂ assimilation, stomatal conductance and transpiration rates were markedly decreased by environmental conditions (high air temperature and high light intensity) during the summer period. At the partial active growth phase of the Chemlali olive cultivar (September–November), a significant re-increase in all parameters was observed. However, net photosynthesis and stomatal conductance of control plants (T0) were, respectively, 57 and 40% lower than those of plants conducted under milder water contribution (T1). The decrease of physiological activity in irrigated plants during hot and dry (summer time) and cold (winter) seasons was a clear evidence that water supply during such periods will be without a great benefit for photosynthetic activity, and thus growth, if applied under critical conditions inducing the rest phase of the plant. The non-statistically significant slight differences as well in photosynthetic performances activities (Pn, Gs and E rates), as in olive production between the two irrigated treatments will not cover the expenses of water loss when applying irrigation at 66% of ET_c especially in arid region characterized by scant and irregular rainfall. On the light of these results, we can conclude that the irrigation of this species during the vegetative growth phase (in spring and autumn), and stopping it during the olive rest phase (in summer and winter) could be recommended at least under the experimental conditions of this study; and that the contribution of 600 mm of water per year (33% of ET_c) can respond to the needs of the Chemlali olive cultivar in a semi arid region without impairing photosynthetic activity and olive production.     

干旱胁迫对苹果叶片中甜菜碱和丙二醛及脯氨酸含量的影响

以盆栽的富士／八棱海棠和新红星／八棱海棠苹果为试材，初步探讨了不同土壤水分状况下甜菜碱含量的变化及其与抗旱性之间的关系。结果表明：在干旱胁迫下，供试品种叶片内的甜菜碱和丙二醛含量均随着胁迫程度的增加呈显著上升趋势，而脯氨酸则是先减少后随着干旱程度的加重含量明显增加。苹果叶片中的甜菜碱含量与丙二醛含量呈正相关，相关系数为0．9130—0．9853，表明甜菜碱含量也是与果树抗旱性密切相关的生理指标。     

Water relations of pistachio (Pistacia vera L.) as affected by phenological stages and water regimes

Pistachio is a drought tolerant fruit tree that can be cultivated in rainfed and irrigated conditions. The water requirements of the tree, however, are considerable so in most of the commercial orchards deficit irrigation is a common practice. Regulated deficit irrigation in pistachio trees has been described in several works, which reported that the phenological stage of shell hardening, so called stage II, is the most drought tolerant. This paper proposes that such drought resistance is related to changes in water relations linked to the phenological stages, even in conditions of no water stress. In order to evaluate such changes, the daily pattern of stem water potential and gas exchange (net photosynthesis, P_n, and leaf conductance, g_s) was measured, determining also the pressure–volume curves, in three different phenological stages of mature pistachio trees (Pistacia vera cv Kerman on P. terebinthus L. rootstock.). The daily pattern of stem water potential and gas exchange were performed in three different irrigation treatments: control, regulated deficit irrigation and rainfed. The pressure–volume curves were made only in the control and rainfed treatments. Significant differences were found in the daily pattern of stem water potential in all the phenological stages considered, while only in the last one the net photosynthesis was affected by water stress. The daily pattern of gas exchange at the beginning of the season was not affected by the evaporative demand, with a constant value when radiation was not limiting. Moderate levels of water stress during the last measurement date reduced the maximum values of g_s and P_n resulting also in a clear change in the pattern of the daily curve, with maximum values only at the beginning of the day. The relationships between stem water potential and gas exchange parameters were different during stage II and almost the same in stages I and III. The parameters drawn from the pressure–volume curves also indicated a change in the elastic modulus of the leaf cells in stage II. In addition, differences in the osmotic adjustment (OA) index suggested different degree of osmotic adjustment of the phenological stages in the response to water stress. The results showed that different mechanisms of drought resistance are operating in the different phenological stages in pistachio trees.     

Effects of Vegetation-Free Strip Width and Irrigation on Newly Planted Peach

Field experiments were conducted at two locations (Clayton and Jackson Springs, NC) to determine the influence of vegetation-free strip width (VFSW) and irrigation on newly planted peach growth and yield in a low-density orchard with a volunteer weedy ground cover. The experiments included VFSW of 0, 0.6, 1.2, 2.4, 3, or 3.6 m under irrigated or nonirrigated conditions. Seasonal variation in the orchard floor vegetation was observed as different weed species reported in summer and winter. However, this difference was not apparent with respect to VFSF and irrigation. At Jackson Springs, NC, the predicted irrigated VFSW which would produce the same trunk cross-sectional area (TCSA) as the grower standard (3-m nonirrigated) was 1.5, 1.3, and 0.8 m for one-, two-, and three-year-old trees, respectively. The predicted irrigated VFSW which would produce the same yield as the grower standard was 1.16 m. At Clayton, TCSA and fruit yield were not different by irrigation, but did increase linearly with VFSW. At both locations, leaf nitrogen (N) concentration was lower in irrigated trees than nonirrigated trees. Leaf N, leaf area, and SPAD were positively related to VFSW at Jackson Springs. In contrast, leaf N concentration was not different by VFSW at Clayton. However, leaf area and SPAD were positively related to VFSW at Clayton. These results suggest that a 1.5 m VFSW combined with proper irrigation and fertilization will produce tree growth and yield in newly planted orchard with volunteer weedy vegetation similar to the current grower standard in the southeastern USA.     

A comparison of winter-sown tomato plants grown with restricted and unlimited water supply

The morphology, anatomy and physiology of winter-sown tomato plants grown with a restricted water supply (producing ‘hard’ plants) were compared with those of plants given an unlimited water supply (‘soft’ plants). The stressed plants had smaller and fewer leaves on thinner stems; the reduction in leaf area was largely due to smaller cell size. The leaves and stems also had a higher percentage dry matter; in the stems this was associated with many more and larger starch grains. It is suggested that the improvement in earliness and in fruit quality found in stressed plants originates from this increase in stored carbohydrate.

Rates of photosynthesis per unit leaf area were the same in both groups of plants when measured under laboratory conditions. The leaf cell sap had the same osmotic potential but there was a greater proportion of apoplastic water in the leaves of the stressed plants. Transpiration rates in the glasshouse were lower in the stressed plants. Possibilities for the control of plant water status to optimize early yield quantity and quality are considered.     

Water relations and yield of lysimeter-grown strawberries under limited irrigation

The effects of partial root-zone drying (PRD), as compared to deficit irrigation (DI) and full irrigation (FI), on strawberry (cv. Honeoye) berry yield, yield components and irrigation water use efficiency (WUE_I) were investigated in a field lysimeter under an automatic rain-out shelter. The irrigation treatments were imposed from the beginning of flowering to the end of fruit maturity. In FI the whole root zone was irrigated every second day to field capacity viz. volumetric soil water content (θ) of 20%; while in DI and PRD 60% water of FI was irrigated to either the whole or one-half of the root system, respectively, at each irrigation event. In PRD, irrigation was shifted from one side to the other side of the plants when θ of the drying side had decreased to 8–11%. Compared to FI plants, leaf water potential was significantly lower in DI and PRD plants in 3 out of 10 measurement occasions, while stomatal conductance was similar among the three treatments. Leaf area, fresh berry yield (FY), individual berry fresh weight, berry water content, and berry dry weight (DW) were significantly lower in DI and PRD plants than those of FI plants; whereas the total number of berry per plant was similar among treatments. Compared with FI, the DI and PRD treatments saved 40% of irrigation water, and this led to a 28 and 50% increase of WUE_I based on berry FY and DW, respectively, for both DI and PRD. Conclusively, under the conditions of this study PRD had no advantage compared to DI in terms of berry yield and WUE_I. DI and PRD similarly decreased berry yield and yield components and thus cannot be recommended under similar conditions.     

Effect of two irrigation rates on yield,incidence of blossom-end rot,mineral content and free amino acid levels in tomato cultivated under drip irrigation using saline water

Summary

An experiment investigated the effects of two rates of irrigation, one of which reflected a substantial degree of water stress, on the mineral content, free amino acid levels and incidence of blossom-end rot (BER) in tomato (Lycopersicon esculentum Mill. `Durinta'). The plants were grown in the open with drip irrigation using saline water from a well (mean EC_w 5.2 dS m²¹). The yield per plant was higher and fewer fruit were affected by BER in the treatment involving the higher level of irrigation. The fruit of the first and fifth truss, and the leaves immediately above, were analysed for their macronutrient, micronutrient and free amino acid content. The macronutrient leaf and fruit content hardly showed any difference, only the N concentration in fruit being significantly affected in the water stressed plants, in which the levels were higher. The Ca concentration in the stylar portion of mature fruit, which is related with the incidence of BER, was not significantly affected by the level of irrigation. As regards micronutrients, only the Fe (in leaf and fruit of the first truss), Cu (in leaf of the first truss), Zn (in leaf and fruit of the first truss, and leaf of the fifth truss) and Mn (in leaf of the first truss) concentrations differed significantly. The total free amino acid leaf content was similar in both irrigation treatments. However, the total free amino acid content of fruit, significantly those of the first truss, was higher in the less irrigated treatment. The amino acids: aspartic acid (only from the first.truss), glutamic acid, proline and alanine had high concentrations in the fruit of the less irrigated plants, while the g-aminobutyric acid and phenylalanine (only from the fifth truss) concentrations were higher in fruit of the more irrigated plants.     

Effects of irrigation with treated wastewater on olive tree growth,yield and leaf mineral elements at short term

In arid regions, such as Tunisia, the reuse of treated wastewater (TWW) in agriculture can be a sustainable solution for water scarcity. A two-year field experiment was conducted in order to investigate the short-term effects of TWW on olive growth, yield and concentration of total nitrogen (N_t), potassium (K), phosphorous (P), and heavy metals (i.e. Zn, Mn, Pb and Cd) in olive leaves. Olive trees were subjected to the following irrigation treatments: (i) trees irrigated with well water (WW) and (ii) trees irrigated with treated wastewater (TWW). For both treatments, the TWW and WW were applied at a rate of 4.5 m³ day⁻¹ tree⁻¹ (5000 m³ ha⁻¹ year⁻¹). After two years, non-significant injuries caused by salts and/or heavy metals were observed on shoot growth of trees irrigated with TWW. The application of TWW significantly increased concentration of N_t, P and K in the leaves, whereas heavy metals (Zn and Mn) showed a significant increase only after the second year of irrigation.     

Water transport in relation to expansion and contraction of leaves and fruits of Calamondin orangef

Diurnal fluctuations in fruit diameter and leaf thickness of Calamondin orange trees were measured and related to transpiration from leaves and to internal redistribution of water from fruits to leaves. While trees were well irrigated, leaf thickness began to decline daily around sunrise and to increase in mid-afternoon. Daily shrinkage and expansion of fruits began later than in leaves. The lag in response of leaf thickness changes to changes in vapour pressure deficit of the air was 1 or 2 hours, whereas the lag in response of fruit diameter was 3 or 4 hours. During imposed droughts, daily shrinkage of fruit and leaves continued until later in the day when the trees were well irrigated. Moreover, during a drought, expansion of the tissues at night occurred at a much slower rate than during periods of daily irrigation, or expansion did not occur at all. Movement of water from fruits to leaves on excised branches was indicated by the higher percentage moisture content of leaves on branches bearing fruits than of leaves on branches without fruits.     

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.     

Detecting different levels of drought stress in apple trees (Malus domestica Borkh.) with selected biochemical and physiological parameters

Rational irrigation scheduling based on sensing drought stress directly in plants is becoming more important due to increasing worldwide scarcity of fresh water supplies. In order to evaluate a set of potential biochemical and physiological stress indicators and select the best drought stress markers in apple trees, two experiments with potted trees and an experiment with intensive orchard grown apple trees ‘Elstar’ and ‘Jonagold Wilmuta’ were conducted in early summer in tree following years. Biochemical parameters: ascorbic acid, glutathione, tocopherols, chlorophylls, carotenoids, free amino acids, soluble carbohydrates, and physiological parameters already known as stress indicators in apple trees: predawn and midday leaf water potential, net photosynthesis (Pn), stomatal conductance (g_s), transpiration (Tr) and intercellular CO₂ concentration (Ci) were measured in leaves of apple trees subjected to different intensities of slowly progressing drought or no drought. Our study pointed out zeaxanthin and glutathione as the best drought stress markers in apple trees. Ascorbate and sorbitol appeared to be reliable indicators of moderate drought only. Responses of other tested biochemical parameters were not consistent enough to prove their role as drought stress markers in apple trees. Relative air humidity should be taken in consideration when physiological parameters g_s, Pn, Tr and Ci are used as drought stress markers in apple trees. Our study revealed that in situations where low relative air humidity affects g_s and with g_s connected physiological parameters, biochemical markers may be better tool for determination of drought stress intensities in apple trees.