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.     

Effect of native habitat on the cooling ability of six nursery-grown tree species and cultivars for future roadside plantings

Vegetation in urban areas provides benefits to people, which are increasingly assessed and valued as ecosystem services (ESS). The regulation of the urban microclimate is one of these services, since trees have the potential to reduce urban heat loads by evapotranspiration and shading. Simultaneously, it has been suggested that trees from dry habitats should be used to cope with the increasing risks of drought under climate change in Central Europe. The underlying properties that enable those trees to reduce dependence on the environment, however, are assumed to come at the expense of biomass production and water loss. In the potentially conflicted area between drought tolerance and ESS we compared water consumption, water-use efficiency (WUE), crown structure and growth of six roadside species/cultivars, which are assumed to vary in drought tolerance, due to differing resource supplies in their native habitats. Acer platanoides, Carpinus betulus ‘Fastigiata’, and Tilia cordata ‘Greenspire’ were compared with Acer campestre, Ostrya carpinifolia, and Tilia tomentosa ‘Brabant’, the latter presumably being less water-demanding. Measurements took place in the municipal nursery of Munich during summer 2016.Surprisingly, the less water-demanding species/cultivars exhibited on average 1.24 times higher values of maximum daily sap flux density and up to seven times higher growth rates, both contributing to higher WUE. Scaled to leaf level, however, their mean daily transpiration rates were on average lower (0.21 and 0.31 kg H₂O m⁻² d⁻¹, respectively). They also showed higher flexibility in response to changing weather with increased growth and transpiration under favorable conditions in early summer, but a more conservative water use in dry late summer. The results suggest that these species/cultivars tend to regulate their water use stronger under increasing dryness, whereas canopy size and leaf amount are still the main important determinants of species and cultivar differences in water use.     

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.     

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.     

Osmotic adjustment,proline accumulation and cell membrane stability in leaves of Cocos nucifera submitted to drought stress

The role of drought-induced proline accumulation in coconut leaves is still unclear. With the objective of evaluating the impact of water shortage on leaf osmotic potential, proline accumulation and cell membrane stability in young plants of two Brazilian Green Dwarf coconut ecotypes from contrasting areas (Brazilian Green Dwarf from Una, Bahia, UGD, and from Jiqui, Rio Grande do Norte, JGD), a pot experiment was conducted under greenhouse conditions. Three drought cycles consisting of suspension of irrigation until the net photosynthetic rate (A) approached zero and rewatering until recovery of A to 85% of the irrigated control plants. Pre-dawn leaf water potential (Ψ_PD) reached −1.2 MPa at the point of maximum stress (PMS). Dry matter production and leaf area were severely reduced by drought treatment in the two ecotypes. Corrected values of osmotic potential were significantly reduced in stressed plants of the two ecotypes. Green dwarf coconut palm showed low osmotic adjustment (from 0.05 to 0.24 MPa) and significant accumulation of proline (from 1.5 to 2.1 times in relation to control) in leaflets in response to water deficit. Considering the growth reduction observed in both ecotypes, proline was not associated to osmoregulation. On the other hand, the absence of membrane damage, as indicated by electrolyte leakage method, suggests that the protective role of proline in this specie can be more important. The two ecotypes of Green dwarf coconut palm behaved similarly in the present experiment for most traits evaluated. Slight differences among the ecotypes were observed with respect to the response to treatments, such as higher proline accumulation in JGD.     

Morphological,anatomical and physiological responses of Campylotropis polyantha (Franch.) Schindl. seedlings to progressive water stress

In this study we implemented a potted water supply experiment for 100 days by a completely random sole-factored design with five treatments: 100% (W₁₀₀), 80% (W₈₀), 60% (W₆₀), 40% (W₄₀) and 20% (W₂₀) of water holding capacity (WHC), corresponding to the soil volumetric water content (SVWC) maintained at 38.8 ± 0.3%, 31.6 ± 1.7%, 25.6 ± 1.3%, 16.5 ± 0.7%, and 8.1 ± 1.1%, respectively. The objective was to evaluate the ability of the 2-month-old Campylotropis polyantha (Franch.) Schindl. seedlings to tolerate drought and to explore the mechanism resisting drought. We monitored the growth process of seedling height and leaf number monthly and further investigated those changes in plant growth, dry mass accumulation and allocation, water-use efficiency (WUE), leaf functional traits, chlorophyll a fluorescence and pigment contents across the water deficit gradient. We found that the seedlings presented optimal growth, dry mass production, and physiological activity only at the W₁₀₀ and W₈₀ treatments and afterwards significantly decreased with progressive water deficit; the WUE was improved under moderate water stress (W₆₀ and W₄₀) but reduced under severe stress (W₂₀). The serious leaf shedding, growth stopping and seedling death under the W₂₀ condition revealed that the current-year shrub seedlings could not withstand severe drought. Water stress-induced decrease in total plant leaf area due to a combination of limited expansion of younger leaves and shedding of old leaves caused the leaf area ratio reduction under drought. The reduced mesophyll cell was a major anatomical response of leaves along the water stress gradient. The progressive water stress significantly damaged light harvesting complex and reduced photochemical processes and PSII activity. Our results clearly showed that the current-year shrub seedlings took the avoidance and tolerance mechanisms to withstand progressive drought stress and around 25.6% SVWC and around 12.3% SVWC separately are thresholds to limit the optimal growth and dry mass production and to last growing and surviving for the current-year shrub seedlings.     

Photosynthetic and growth responses of juvenile Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) to waterlogging and water deficit

Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) are leafy vegetable crops grown in south-east Asian countries where rainfall varies dramatically from excess to deficit within and between seasons. We investigated the physiological and growth responses of these plants to waterlogging and water deficit in a controlled experiment in a glasshouse. Juvenile plants were subjected to waterlogging or water deficit for 19 days in case of Chinese kale and 14 days in case of Caisin and compared with well-watered controls. Caisin tolerated waterlogging better than Chinese kale because it produced hypocotyl roots and gas spaces developed at the stem base. In Chinese kale, waterlogging reduced plant fresh weight (90%), leaf area (86%), dry weight (80%) and leaf number (38%). In contrast, waterlogging had no impact on leaf number in Caisin and reduced plant fresh and dry weights and leaf area by 60–70%. Water deficit reduced leaf area, fresh weight and dry weight of both species by more than half. Leaf number in Chinese kale was reduced by 38% but no effect occurred in Caisin. Water deficit increased the concentration of nitrogen in the leaf dry matter by more than 60% in both species and the leaf colour of water deficient plants was dark green compared with the leaf colour of well-watered plants. Soil water deficit delayed flowering of Caisin while waterlogging accelerated it. Thickening and whitening of the cuticle on the leaves of Chinese kale probably increased its ability to retain water under drought while Caisin adjusted osmotically and Chinese kale did not. Waterlogging and water deficit had strong effects on leaf gas exchange of both Brassica species. Water deficit closed the stomata in both species and this was associated with a leaf water content of 9 g g⁻¹ DW. In contrast, waterlogging reduced conductance from 1.0 to 0.1 mol H₂O m⁻² s⁻¹ in direct proportion to changes in leaf water content, which fell from 11 to 5 g g⁻¹ DW. This separation of the effects of water deficit and waterlogging on conductance was reflected in transpiration, internal CO₂ concentration and net photosynthesis. In conclusion, Chinese kale and Caisin showed rather different adaptations in response to waterlogging and water deficit. Caisin was more tolerant of waterlogging than Chinese kale and also showed evidence of tolerance of drought. There is genetic variation to waterlogging within the Brassica genus among the leafy vegetables that could be used for cultivar improvement.     

ISSR variations in eggplant (Solanum melongena L.) and related Solanum species

Inter-simple sequence repeat (ISSR) analysis was performed in eight cultivars of eggplant (Solanum melongena) and 12 accessions in eight related Solanum species to evaluate the applicability of this analysis for assessing the phylogenetic relationships and identifying cultivars. A total of 552 polymorphic amplified bands were obtained from 34 of the 100 primers tested, and the percentage of polymorphisms was 99.1%. Cluster analysis based on the ISSR markers classified the Solanum species into seven groups: (i) S. melongena; (ii) S. aethiopicum and S. anguivi; (iii) S. incanum; (iv) S. violaceum and S. kurzii; (v) S. macrocarpon; (vi) S. virginianum and (vii) S. torvum. Combining the ISSR markers obtained by a few of the 34 primers was enough for distinguishing of the eight cultivars of eggplant. This ISSR analysis was demonstrated to be available for the phylogenetic study and the cultivar identification.     

Effect of increasing climatic water deficit on some leaf and stomatal parameters of wild and cultivated almonds under Mediterranean conditions

The prevailing environmental conditions, temperature in particular, drive seasonal changes both in leaf development and stomatal characteristics. In order to ascertain the effect of increases in climatic water deficit on some leaf and stomatal parameters under field conditions, a study was carried out on two sets of leaves (spring and summer) on a large sample of Amygdalus communis L. cultivars in comparison with several Amygdalus webbii Spach seedlings, a species more adapted to arid environments and probable ancestor of cultivated almonds. Observations were performed between spring and summer of a particularly hot season. The results showed a significant and general reduction of both leaf area and stomatal frequency and an increase in stomatal size. Nevertheless, there were evident differences between cultivated and wild almonds. A stronger reduction of leaf area was observed in A. webbii (−31%) with respect to A. communis (−14%); on the contrary, the latter reduced stomatal frequency more than the former (−25% and −19%, respectively). The examined cultivated almonds, in response to the increase in climatic water deficit, tended to arrange their stomatal structures like those of wild almonds. Finally, increasing the climatic water deficit, the slope of the linear regressions between stomatal frequency and size did not change in either species, leading to a better understanding of the mechanisms of almond acclimation to environmental stresses.     

Leaf anatomical characteristics and physiological responses to short-term drought in Ziziphusmauritiana (Lamk.)

The aim of this work was to study the association between leaf anatomical characteristics and response to short-term drought stress in Ziziphusmauritiana Lamk. Six Z. mauritiana cultivars (Seb, Gola, Umran, Keitly, Q-29 and B-5/4) under field conditions in Israel's Negev desert were studied. Width of palisade mesophyll, spongy mesophyll and epidermis, xylem number and diameter in mid-vein were investigated with light microscopy. Short-term (3 weeks) drought stress tolerance was evaluated by monitoring plant response (leaf transpiration, diffusive resistance, chlorophyll fluorescence, leaf water potential and leaf relative water content). Greater epidermis and mesophyll widths and xylem diameters and densities were associated with increased tolerance to short-term water deficit expressed by preliminary wilting symptoms and proportional differences between initial and final physiological parameters. Significantly larger differences were found in Keitly, Umran and B-5/4 than in Seb, Gola and Q-29, indicating that the former cultivars are more sensitive to drought stress. Our results indicate that tolerance in descending order was Seb, Q-29, Gola, B-5/4, Keitly and finally Umran. The existence of an association between anatomical characteristics and short-term drought stress tolerance based on physiological responses is suggested.     

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.     

Drought responses of six ornamental herbaceous perennials

Although low water use landscaping is becoming common in arid regions, little is known about drought tolerance and drought responses of many ornamental plants, especially herbaceous perennials. Drought responses were assessed for six herbaceous ornamental landscape perennials in a 38 l pot-in-pot system in northern Utah over a 2-year period. The first year was an establishment period. During the second year, drought responses were evaluated for established Echinacea purpurea (L.) Moench, Gaillardia aristata Pursh, Lavandula angustifolia P. Mill., Leucanthemum × superbum (J.W. Ingram) Berg. ex Kent, ‘Alaska’, Penstemon barbatus Roth var. praecox nanus rondo, and Penstemon × mexicali Mitch. ‘Red Rocks’. Plants were irrigated at frequencies of 1 (control), 2, or 4 weeks between June and September, simulating well-watered conditions, moderate drought, or severe drought. Osmotic potential (Ψ_s), gas exchange, visual quality, leaf area, and dry weight were assessed. In a confined root zone, P. barbatus showed the greatest tolerance to all levels of drought, avoiding desiccation by increasing root:shoot ratio and decreasing stomatal conductance as water became limiting. L. angustifolia and P. × mexicali showed tolerance to moderate drought conditions, but died after exposure to the first episode of severe drought. Neither G. aristata nor L. superbum were able to regulate shoot water loss effectively. Instead, both species displayed drought avoidance mechanisms, dying back when water was limiting and showing new growth after they were watered. Compared to control plants, G. aristata shoot dry weight was reduced by 50% and 84%, and L. superbum shoot dry weight was reduced by 47% and 99% for the 2- and 4-week irrigation intervals, respectively. Root dry weights were affected similarly for both species. E. purpurea exhibited poor visual quality at all irrigation intervals, in particular wilting severely in both drought treatments, but regaining turgor when watered again. P. barbatus is recommended for ornamental landscapes that receive little or no supplemental irrigation, while E. purpurea is not recommended for low water landscapes because of low visual quality under even mild drought.     

Effects of water stress and re watering on ribulose-1,5-bis-phosphate carboxylase activity,chlorophyll and protein contents in two cultivars of tomato

Summary

The effects of water deficit and rewatering on ribulose-1,5-bis-phosphate carboxylase activity, chlorophyll and protein content were evaluated in plants of two cultivars of tomato. During the water deficit period, values of water potential, osmotic potential and relative water content decreased along with associated decreases in RuBPcase activity, protein content and chlorophyll content, being less marked for chlorophyll content. There was a significant correlation of RuBPcase activity and protein content with components of leaf water status from plants under water stress. The associated decrease of RuBPcase, chlorophyll and protein contents with decreased osmotic potential during the development of water deficit was evident. At the time the plants reached a water potential of –1.40 to –1.56 MPa (RI: first level of recovery after water stress), one group of plants was rewatered. The rest were kept under stress until the water potential reached values of –2.30 to –2.51 MPa (RII: second level of recovery after water stress). It was observed that all of the varieties measured at both levels (RI and RII) showed a gradual recovery, reaching or even surpassing the values of control plants.     

Horticultural performance of ‘Folha Murcha’ sweet orange onto twelve rootstocks

Despite its outstanding position, the Brazilian citriculture is established on a very limited pool of varieties that limits its expansion and restricts the fruit availability throughout the year. This situation determines the urgent necessity of developing alternative scion and rootstock cultivars, with good performance under local conditions. ‘Folha Murcha’ sweet orange (Citrus sinensis (L.) Osbeck) is a late-harvest cultivar, suitable both for the juice processing industry and the fresh fruit market, being described as tolerant to citrus canker (Xanthomonas citri subsp. citri Schaad et al.), and less affected by citrus variegated chlorosis (Xylella fastidiosa Wells et al.). A study was conducted in Bebedouro, São Paulo State, Brazil, to evaluate the horticultural performance of ‘Folha Murcha’ sweet orange budded onto 12 rootstocks: the citrandarin ‘Changsha’ mandarin (Citrus reticulata Blanco) × Poncirus trifoliata ‘English Small’; the hybrid ‘Rangpur’ lime (Citrus limonia Osbeck) × ‘Swingle’ citrumelo (P. trifoliata (L.) Raf. × Citrus paradisi Macfad.); the trifoliates (P. trifoliata (L.) Raf.) ‘Rubidoux’, ‘FCAV’, and ‘Flying Dragon’ (P. trifoliata var. monstrosa); the ‘Sun Chu Sha Kat’ mandarin (C. reticulata Blanco); the ‘Sunki’ mandarin (Citrus sunki (Hayata) Hort. ex. Tanaka); the ‘Rangpur’ limes (C. limonia Osbeck) ‘Cravo Limeira’ and ‘Cravo FCAV’; ‘Carrizo’ citrange (C. sinensis × P. trifoliata), ‘Swingle’ citrumelo (P. trifoliata × C. paradisi), and ‘Orlando’ tangelo (C. paradisi × Citrus tangerina cv. ‘Dancy’). The experimental grove was planted in 2001, using a 7 m × 4 m spacing, in a randomized block design, with five replications and two plants per plot. No supplementary irrigation was applied. Fruit yield, canopy volume, tree tolerance to drought and to citrus variegated chlorosis, and fruit quality were assessed for each rootstock. Trees grafted onto the ‘Flying Dragon’ trifoliate were smaller in size, but had largest yield efficiency when compared to those grafted onto other rootstocks. Lower alternate bearing index was observed on trees budded onto ‘Cravo FCAV’ ‘Rangpur’ lime. Both ‘Rangpur’ lime rootstocks and the ‘Sunki’ mandarin induced higher tree tolerance to drought. The ‘Flying Dragon’ trifoliate induced better fruit quality and higher tolerance to citrus variegated chlorosis (CVC) to ‘Folha Murcha’ trees. A cluster multivariate analysis identified three groups of rootstocks with similar effects on ‘Folha Murcha’ tree performance. Among the 12 evaluated rootstocks, the ‘Flying Dragon’ trifoliate has a unique effect on plant growth, tolerance to drought and CVC, fruit yield and fruit quality of ‘Folha Murcha’ trees, and may be better suited for high-density plantings.     

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.     

土壤干旱和复水对结缕草生理特性的影响

通过对结缕草在土壤干旱及复水过程中叶片相对含水量(RWC)、游离脯氨酸含量(Pro)、叶绿素含量、超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量、可溶性糖(TSC)含量等生理指标的测定,研究土壤干旱对结缕草生理特性的影响.结果表明:干旱胁迫引起结缕草的叶片相对含水量明显下降,游离脯氨酸含量、丙二醛含量及可溶性糖含量均随干旱天数的增加呈持续增加的趋势,而叶绿素含量和SOD酶活性先增后减.复水后各项生理指标除相对含水量、游离脯氨酸含量外均随着复水时间的增加逐渐恢复至对照水平.干旱胁迫下,结缕草水分平衡的保持、SOD酶活性及丙二醛含量的增加以及脯氨酸和可溶性糖等渗透调节物质的积累,是结缕草抗旱的重要生理机制.     

Identification of S-alleles in pear (Pyrus communis L.) cv. ‘Rocha’ and other European cultivars

In this work we report the cloning and identification of S-RNase alleles responsible for gametophytic self-incompatibility (GSI) of ‘Rocha’ pear and of 13 other European pear cultivars that might be used as its pollinators. Partial sequences of S-RNase alleles were amplified by PCR with specific primers hybridising in conserved regions of previously identified S-RNase alleles of Pyrus communis, cloned and sequenced and the S-genotype of eight pear cultivars was fully determined. Three cultivars (‘General Léclerc’ (SqSl), ‘Tosca’ (SbSl) and ‘Alexandrine Douillard’ (SbSk)) shared no S-alleles with ‘Rocha’ (SaSe) and shall be totally compatible with this cultivar. None of the cultivars analysed showed an identical amplification pattern to the one observed in ‘Rocha’, so the other cultivars shall be at least semi-compatible. One new allele was identified in P. communis cv. ‘Beurré d’Avril’ (designated as St). The determination of both S-RNase alleles of cvs ‘Rocha’, ‘Beurré Precoce Morettini’ (SeSk) and ‘Tosca’ and the identification of one S-RNase allele in cvs ‘Carapinheira’ (Sb), ‘Amêndoa’ (Se), ‘Pérola’ (Sk) and ‘Beurré d’Avril’ (St) are important contributions for the effort recently developed worldwide to establish groups of sexual compatibility among European pears.     

部分梨砧木的叶片组织结构与抗旱性的关系

为了评价西南喀斯特山区常用梨砧木的抗旱力强弱,了解其叶片组织解剖结构和保水力参数与抗旱性的关系,以川梨(Pyrus pashia Buch.-Ham.)、滇梨(P.pseudopa shia Yu)、砂梨(P.pyrifolia Nakai)和杜梨(P.betulaefolia Bge.)为材料,采用测定旱害指数的方法鉴定其抗旱力强弱,分析几种梨砧木叶片组织解剖结构和保水力参数与抗旱性的关系。结果表明,供试梨砧木的实际抗旱力强弱顺序为杜梨>川梨和滇梨>砂梨。梨砧木叶片栅栏组织与海绵组织的厚度比、叶肉组织结构紧密度(CTR)和水分临界饱和亏的大小,与砧木种间的旱害指数呈极显著的负相关,与抗旱性呈极显著的正相关;叶肉组织结构疏松度(SR)和失水速率的大小,与旱害指数呈极显著的正相关,与抗旱性呈极显著的负相关。杜梨的抗旱力极强,川梨和滇梨抗旱力强,砂梨的抗旱力中等。用叶片组织解剖结构参数指标鉴定梨砧木抗旱性可靠性较强,用叶片失水速率和水分临界饱和亏等指标鉴定梨砧木抗旱性与实际抗旱性具有较高的吻合度。