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.     

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.     

Seasonal impact on physiological leaf damage risk of Aechmea hybrid under greenhouse conditions

For decades bromeliad growers have to face severe leaf damage problems occurring as necrotic spots on leaves of sensitive CAM plants such as Aechmea, both in cultivation and transport. These physiological problems mainly arise during the summer period from June to September. Previous research made clear that high malic acid concentrations in the early morning generate the driving force for cellular osmotic uptake of water and can consequently induce lethal turgor pressures in sensitive Aechmea cultivars. Although it is commonly known that CAM and its related metabolites can be influenced by different environmental factors, this relationship is poorly investigated under commercial greenhouse conditions.Therefore the authors carried out four seasonal diurnal experiments with a high leaf damage sensitive Aechmea cultivar spread equally over a 1-year period. Malic acid dynamics revealed that during the critical summer period plants fail to induce malic acid consumption in the early morning causing prolonged high levels of malic acid in the leaves. Moreover, relative water content measurements did confirm that enough water is always available inside the leaves and that even slight changes in water status can be disastrous for the leaves. During the rest of the year malic acid is consumed early in the morning and is not long enough available in the leaf to cause lethal water flow. The comprehension of why this damage induction mechanism is closely related with the summer period is essential to search for possible solutions to prevent the appearance of this physiological leaf damage problem in the future.     

Guide for Authors

Bromeliad growers report severe leaf quality problems for Aechmea cultivars grown under commercial greenhouse conditions. In this research, a leaf damage ‘sensitive’ and ‘insensitive’ A. cultivar were compared for their C-metabolism and hydrophysiology under these greenhouse conditions. Stomata opening index indicated CAM (Crassulacean acid metabolism) for both cultivars, with 45–50% open stomata around 4:00 a.m. and 5–10% in the afternoon. Malic and citric acid were the major organic acids present in the leaves, with diurnal malic acid accumulation during the night. The leaf damage ‘sensitive’ cultivar showed higher malic acid accumulation than the ‘insensitive’ cultivar (200 μmol/gfw versus 170 μmol/gfw). Leaf osmotic potential and turgor pressure were linked with diurnal malic acid fluctuations: organic acid accumulation during the night generated high leaf turgor pressures (up to +0.86 MPa).A leaf damage sensitivity test was designed and confirmed previous experiences of several bromeliad growers. Both cultivars showed higher leaf damage percentages (98 and 78%) when leaf malic acid accumulation was high. We attribute this elevated sensitivity to lethal turgor pressures and consider them to be caused by the water capturing mechanism generated by high organic acid accumulation. Under current greenhouse conditions, this water capturing mechanism can be disastrous for plant leaf quality. Especially, under high relative humidity, hindering plant transpiration and stimulating water uptake by dew formation, leaf quality could be endangered.     

Determination of the mechanical properties of the grape berry skin by hydraulic measurements

Theory and instrumentation are presented for determination of the mechanical properties of the grape berry skin. Water under pressure is slowly injected into the grape berry and the pressure and the increase of volume are measured. The stress and the strain in the skin are calculated and presented in the form of a stress-strain diagram. The pressure may be increased until the burst strength of the skin is reached. Examples of measurements are given and discussed. The method may be used to select cultivars resistant to splitting and for the investigation of the properties of the berry which are related to its turgor pressure.     

Moderating water stress in tomato (Lycopersicon esculentum Mill.) plants by application of specific nitrogen doses

Summary

The effect of different doses of nitrogen on water stress in tomato (Lycopersicon esculentum Mill. ‘Royesta’) plants grown in a sandy soil and exposed, or not, to long-term water stress was studied. Nitrogen dose treatments consisted of Hoagland’s solution (N1 treatment), Hoagland’s solution + 40 mM NO₃^– (N2 treatment), or Hoagland’s solution + 80 mM NO₃^– (N3 treatment) applied every 3 d, for a total of seven applications following plant establishment. Subsequently, daily application of 80% (stressed) or 100% (unstressed) of the water evapotranspired by control plants the previous day was combined, factorially, with the three nitrogen treatments, for a period of 2 weeks. The leaf fresh weight (FW) at full turgor:leaf dry weight (DW) ratio was high in plants under the N1 and N3 stress treatments, with no significant difference between them soon after the start and at the end of the water stress treatment. However, the N2 treatment produced a significant increase in the ratio in well-watered plants, but not in water-stressed plants at the end of the stress period. The surface area per leaf was greater in stressed than in control plants, except for N2. Leaf water potential was greatly reduced in stressed N2 and N3 plants, but was unaltered in their well-watered counterparts. The significant increases in relative water content at the turgor loss point (around 3%) and in cell membrane rigidity (an increase of more than 125% in the bulk modulus of elasticity) clearly indicate an osmotic adjustment in stressed N2 plants, confirming that this N dose moderated the effects of the water stress imposed on N2 plants.     

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。     

Effect of cold and drought stress on blueberry dehydrin accumulation

Summary

Dehydrins are a group of plant proteins which respond to any type of stress that causes dehydration at the cellular level, such as cold and drought stress. Previously, three dehydrins of 65, 60, and 14.kDa were identified as the predominant proteins present in cold acclimated blueberry (Vaccinium corymbosumLinn.) floral buds. Levels were shown to increase with cold acclimation and decrease with deacclimation and resumption of growth. In the present study, to determine if dehydrins are induced in other organs in response to low temperature treatment (48C) and in response to drought, accumulation of dehydrins was examined in leaves, stems, and roots of two cultivars and one wild selection (a V. corymbosum cultivar, a V. ashei Reade cultivar, and a V. darrowi Camp selection) of blueberry by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting. Cold treatment involved placing plants in a cold room maintained at 48C for five weeks; drought stress was imposed by withholding water from potted, greenhouse-grown plants for 34.d. Relative water content (RWC) of shoots was determined periodically throughout the drought treatment. Dehydrins accumulated with both cold and drought stress but their molecular masses varied depending upon blueberry species. Dehydrins accumulated to higher levels in stems and roots than in leaves with cold stress and to higher levels in stems than in either roots or leaves with drought stress. Furthermore, cold treatment combined with dark treatment induced higher levels of dehydrins than cold treatment combined with a 10.h light/14.h dark photoperiod, suggesting that dehydrins may be responsive to changes in photoperiod as well. In the cold-stress experiment, the level of dehydrin accumulation was correlated with expected level of plant cold hardiness in the three genotypes. In the drought stress experiment, dehydrins accumulated prior to significant changes in RWC, and dehydrin levels did not appear to be closely correlated with RWC either among or within genotypes.     

Cuticular cracking in pepper fruit. I. Effects of night temperature and humidity

Summary

The objective of the present study was to characterize some of the anatomical and physiological characteristics of fruit cracking in bell pepper (Capsicum annuum L.). Scanning-electron micrographs show that initiation of fruit cracking in bell pepper is by formation of mini-cracks on the cuticle layer; these then enlarge into cracks and traverse the epidermal cells. Pepper cultivars differ in their sensitivity to cracking, partly because of differences in fruit pericarp thickness. Limitation of night transpiration by high humidity or low temperature increased the turgor potential of the fruit pericarp and enhanced cracking. Likewise, leaf pruning suppressed night transpiration and concomitantly increased cracking. Fruit cuticle transpiration was found to be low in the early stages of fruit development and to increase as the fruit became susceptible to cracking. Environmental conditions which enhanced cracking also increased cuticle transpiration in a sensitive pepper cultivar but not in a less sensitive one. We suggest that fruit cracking in bell pepper occurs because reduction in night transpiration causes high turgor pressure in the fruit. As the cuticle becomes permeable to water, the inner turgor pressure causes the cuticle to crack. Differences in cultivar sensitivity may be partly due to differences in pericarp thickness and cuticle properties, but additional factors may be involved.     

Differences in ovary size among olive (Olea europaea L.) cultivars are mainly related to cell number,not to cell size

Differences in mature fruit size among olive cultivars are related to differences in ovary size at bloom, but it is not known whether cell number or size determines the variation in ovary size. In this study we measured cell size and number in equatorial cross-sectional areas of the principal ovary tissues (mesocarp and endocarp) in eight cultivars with very different fruit and ovary size. The results showed that cell number explained most of the differences in ovary size, while cell size was not related to ovary size, except for a weak (R² = 0.33) correlation in the endocarp. Since sink strength is thought to be related to cell number, this finding supports the hypothesis that larger ovaries represent stronger sinks. The implications of greater sink strength with bigger ovaries are discussed. Within cultivars, while the cross-sectional areas of mesocarp and endocarp were similar, cell number was higher in the mesocarp but cell size was smaller compared to the endocarp.     

对羟基苯甲酸胁迫下尖孢镰刀菌侵染草莓根系的组织结构观察

以‘丰香’（Toyonoka）和‘土特拉’（Tutela）草莓品种为试材,利用石蜡切片技术研究了在自毒物质对羟基苯甲酸胁迫下,尖孢镰刀菌草莓专化型（Fusarium oxysporum f. sp. fragariae）侵染根系引起的组织结构变化。结果表明：对羟基苯甲酸胁迫下,尖孢镰刀菌菌丝在‘丰香’和‘土特拉’根系中的侵染速率明显加快,对根系表皮、皮层、中柱薄壁细胞及导管壁结构的破坏程度也明显加重,且对‘丰香’的破坏程度明显重于‘土特拉’。对羟基苯甲酸胁迫显著提高了‘丰香’和‘土特拉’根系组织含菌丝导管的比例,分别为22.5%和15.8%;但‘土特拉’根系含胶状物导管的比例为26.3%,明显高于‘丰香’（16.3%）。在对羟基苯甲酸胁迫下,‘土特拉’根系组织产生胶状物比‘丰香’早。‘土特拉’单独接菌处理根系内含有侵填体导管的比例为1.6%,明显高于‘丰香’单独接菌处理和对羟基苯甲酸胁迫下‘土特拉’接菌处理（1.0%和1.2%）。对羟基苯甲酸胁迫下接种尖孢镰刀菌可明显加重草莓根系组织受损程度,且‘丰香’枯萎病发生较重。     

土壤水分对西瓜幼苗生长的影响

以种子大小不同的4个品种为试验材料,研究了土壤水分胁迫条件下西瓜幼苗的生长状况和几个生理特性变化。结果表明:种子大的品种,幼苗个体大,素质好,苗期生长状况也好;土壤水分条件对西瓜幼苗生长具有显著影响,地上部干物质积累量随着土壤含水率降低而降低,但根系干物质积累量与土壤水分呈负相关;在土壤水分胁迫下,西瓜大种子品种具有大根系吸水优势,而小种子品种以较小蒸腾面积和较强叶片保水能力为适应对策。     

Enzyme activity changes in relation to internal browning of Raphanus roots sown early and late

Summary

Early sown radish seedlings were subjected to heat stress from the middle to late growth stage. Roots exhibiting internal browning (IB) were more prevalent in the susceptible cultivars whose seeds were sown early in the summer compared with those which were sown late. However, IB occurrence in the resistant ones was not nearly so marked regardless of the sowing date. In the IB susceptible cultivars, higher levels of L-phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) activities were detected in roots from the early sown plot (ESP), but these enyzme inductions did not occur to a significant extent in the resistant ones. Roots suffering internal browning were also detected to have pronounced increases in ascorbate peroxidase (APX) activity, but decreases in both dehydroascorbate reductase (DHAR) and glutathione reductase (GHAR) activities. These observations strongly suggest that a decline in H₂O₂ decomposing capacity of the ascorbate-glutathione cycle by heat stress is responsible for the activation of H₂O₂ detoxyifying pathway derived from PPO.     

Effects of water and salt stresses on growth,water relations and gas exchange in Rosmarinus officinalis

Summary

Plants of Rosmarinus officinalis were submitted to water and salt stress, independently. The effects of water or salt stress on growth, water relations and gas exchange were investigated in order to understand the tolerance and adaptative mechanisms of R. officinalis to these types of stress. Under both stress conditions, plants developed avoidance mechanisms to minimise water loss based on morphological and physiological changes (e.g., reduction of plant biomass and leaf area, stomatal closure). Only under salt stress conditions were treated plants able to maintain turgor via osmotic adjustment, which was achieved by the uptake of Na⁺ and Cl^– ions. Osmotic adjustment was not observed in R. officinalis plants submitted to water stress. The results indicate that high accumulation of Na⁺ and Cl^– ions was responsible for the growth reduction observed in salinised plants. However, the growth reduction observed in water-stressed plants was caused by a dehydration process.     

The effect of pre-planting desiccation stress and root pruning on the physiological condition and subsequent field performance of one year old Prunus avium and P. cerasifera seedlings

Summary

Severe desiccation of dormant seedlings of wild cherry (Prunus avium) and cherry plum (P. cerasifera) did not affect their immediate survival, but caused significant reductions in subsequent shoot growth and root volume which were not recovered in a single growing season. Damage to the fine roots, as indicated by the physiological plant quality measures of tetrazolium absorbance and root electrolyte leakage, increased rapidly over drying periods of ca. 6 h, further damage requiring progressively longer periods of desiccation. Root pruning prior to planting did not mitigate desiccation damage and severe pruning was highly injurious to subsequent growth. Generally the removal of the fine roots was equivalent to a relatively short desiccation period, but pruning of fine roots prior to, instead of after, desiccation in P. cerasifera resulted in more lateral shoots, possibly indicating the production of growth retardant substances by the dried root systems. All measures of physiological plant quality at the beginning of the growing season were effective as predictors of plant performance at the end. In the species tested, the most cost-effective routines are likely to be fine root electrolyte leakage and root moisture content, with tetrazolium testing and stem water potential measurements requiring both greater reproducibility and more sophisticated equipment.     

A 3-Year Adaptation Study of Three Distinct Grapevine Cultivars under Midwestern Field Conditions

Simultaneous responses of American (Concord), European (Pinot Noir), and American-European hybrid (Traminette) cultivars to seasonal and diurnal variation in field environmental conditions were assessed to propose suitable cultivars for potential use for selection and breeding in grapevines in dry areas. ‘Pinot Noir’ had higher gas exchange parameters, higher water potential, and chlorophyll fluorescence, while ‘Concord’ had the lowest values in all three seasons and experienced moderate stress by the end of each season. The dry conditions in 2005 caused water potential to decline sharply compared to values recorded in 2004 and 2006. ‘Pinot Noir’ and ‘Traminette’ exhibited a mild stress, while ‘Concord’ exhibited a moderate stress in 2006. Photosynthetic rate decreased slightly during the summer with a slight recovery at the beginning of September, and did not differ across the seasons among cultivars. Stomatal conductance followed the same pattern. However, in both 2004 and 2005, stomatal conductance dropped sharply late in the season because of frequently occurring high temperatures that were greater than 32 °C. Maximum morning values of Fv/Fm were within the optimal range. The study suggests the presence of marginal photoinhibition during mid-summer in Concord cultivars, because no full recovery of photochemical efficiency early in the evening was observed. The European cultivar (Pinot Noir) and the American-European hybrid (Traminette) are more adapted to field conditions in Kansas than Concord cultivars. However, high cold-mortality of Pinot Noir due to high sensitivity to cold winter temperature makes the hybrid cultivars the most suitable cultivar for Midwest regions with relatively cold winters.     

Response to water stress of some oleander cultivars suitable for pot plant production

Oleander (Nerium oleander L.) is an evergreen shrub of great ornamental interest which, in recent times, has been increasingly used as a flowering pot plant. Plants grown in pots undergo more frequent water stress conditions than those grown in the soil, due to the limited volume of substrate available for the roots. Oleander is a species adaptable to dry conditions and able to survive long periods of drought. It is well known that under water stress conditions all plants reduce photosynthetic activity, resulting in reduced plant growth. In case of severe water stress, leaves undergo strong wilting and senescence resulting in the loss of ornamental value. In the present work, a study was conducted to evaluate the ecophysiological response to water stress in four oleander cultivars previously recognised (on the basis of traits such as size, habit, earliness, abundance and duration of flowering, aptitude for cutting propagation and rapidity of growth) as suitable for pot plant production. Our data confirm the high drought tolerance of oleander. In the studied cultivars, plants submitted to water stress showed only minor variations in leaf gas exchange parameters [transpiration (E), stomatal conductance (g_s) and CO₂ net assimilation (A)] for at least 10 days without a change in leaf water content [assessed as relative water content (RWC)] for 22 days from the beginning of the stress treatment. During this period, non-irrigated plants maintained the same water status as control plants and were visually undistinguishable from them. Moreover, plants survived without water supply for one month. Following the supply of water again, they were able to restore RWC, gas exchange parameters and instantaneous water use efficiency [A/E ratio (WUE_inst)] to the values of control plants. Furthermore, if at the end of the stress period plants appeared withered and were pale green in colour, they regained their normal appearance after they were irrigated again. Although the four studied cultivars showed some minor differences in leaf gas exchange parameters and in the manner in which the latter parameters changed after irrigation was stopped, the response to water stress was essentially the same. Therefore, as far as drought tolerance is concerned, all these cultivars have a good aptitude for use as flowering pot plants.     

The effect of water deficit stress on the growth,yield and composition of essential oils of parsley

Three parsley cultivars (plain-leafed, curly-leafed and turnip-rooted) were grown under conditions of 35–40% and 45–60% water deficit in order to evaluate the effect of this form of stress on plant growth, essential oil yield and composition. Plant growth (foliage and root weight, leaf number) was significantly reduced by water stress, even at 30–45% deficit. Water stress increased the yield of essential oil (on a fresh weight basis) from the leaves of plain-leafed and curly-leafed, but not turnip-rooted, parsley. However, on a m² basis foliage oil yield increased significantly only in curly-leafed parsley. Water stress also caused changes in the relative contribution of certain aroma constituents of the essential oils (principally 1,3,8-p-menthatriene, myristicin, terpinolene + p-cymenene), but these changes varied between cultivars. The oil yield of roots was low and water deficit stress had relatively little effect on the root oil composition. It is concluded that because the biomass of plants subjected to water deficit is reduced, it is possible to increase the plant density of plain-leafed or curly-leafed parsley, thereby further increasing the yield of oil per m². However, the application of water deficit stress to parsley essential oil production must also take into account likely changes in oil composition, which in turn relate to the cultivar.     

Investigations on Chlorosis of Fruit Trees.: II.—The Composition of Leaves,Bark and Wood of Current Season’s Shoots in Cases of Lime-Induced Chlorosis.

Summary

Radish (Raphanus sativus) is an important crucifer vegetative crop in Japan. We studied the morphological and anatomical characteristics of radish roots over a 6-week period using three radish cultivars with three different root shapes: long-type (Lt), round-type (Rt), and thin-type (Tt). We found that significant differences in the thickness of the roots first appeared 4 weeks after sowing. In Lt and Rt plants, the roots thickened rapidly, especially in the middle section that is composed of the lower part of the hypocotyl and the upper part of the taproot. The taproot increased in length in Lt plants, but failed to elongate in Rt plants. In Tt plants, the roots showed much smaller increases in mean diameter and length. Transverse sections through the taproots showed significant differences, both in cell number and in cell size 4 weeks after sowing. Lt and Rt plants contained more cells in the secondary xylem and phloem than Tt plants, and cell expansion was also greater in the storage roots of the Lt and Rt cultivars. These results will contribute to a better understanding of the development of radish roots of different shape.     

Evaluating variability of root size system and its constitutive traits in hot pepper (Capsicum annum L.) under water stress

The importance of root size system has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability in root size system of hot pepper at maturity; (ii) estimate the effect of root size system on yield under drought conditions; and (iii) effect of water stress on xylem vessel development and total xylem cross-sectional area in roots of hot pepper cultivars. Twelve diverse hot pepper cultivars were grown in wooden boxes with two different water treatments, normal and in 50% water application as water deficit condition. Mean primary root length (PRL) showed a significant positive correlation with final fruit yield at normal as well as stressed condition. Total dry mass of fruit was reduced by 34.7% in drought treatments (DI) compared to full watered treatment (FI). At harvest, water-stressed plants had 21% lower root dry weight mass but higher root:shoot ratio other than FI. PRL, lateral root density, total xylem area per root cross-section showed a significant positive relationship with fruit yield. Also, lateral root density was higher in cultivars with higher xylem density, particularly in tolerant cultivars. Lateral root density (r = 0.847, P < 0.001) and total xylem cross-sectional area in root (r = 0.926, P < 0.001) were tightly related with total biomass production. The importance of root traits contributing to withstand drought in hot pepper is discussed.