Photosynthetic and physiological responses to high temperature in grapevine (Vitis vinifera L.) leaves during the seedling stage

To study the effects of high temperature (HT) on grape growth, a controlled experiment with grapevine (Vitis vinifera L., cv. Hongti) was conducted from July to October, 2015. The HT treatments were 34, 36, 38, and 40°C, with 28°C as control. The changes to photosynthetic pigment characteristics, antioxidant enzyme activities, and relative water content (RWC) under different HTs were investigated. Severe chlorosis was observed during the late stages of HT treatment. Chlorophyll a (Chl a), chlorophyll b (Chl b), photosynthetic rate at irradiation saturation (P_max), light saturation point (LSP), apparent quantum efficiency (AQE), peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activity in grape leaves increased at first, and then decreased under high-temperature stress (HTS), but the light compensation point acted contrary to the LSP. The carotenoid, malondialdehyde and relative electrical conductivity (REC) increased under HTS; and the Chl/carotenoid ratio and RWC were contrary to the REC. The results suggested that grapes subjected to 38°C for 4 d decreased their RWC, but Chl a, Chl b, P_max, AQE, LSP, SOD, POD, and CAT reached their maximums. Therefore, the high-temperature limit of Hongti was 38°C and the duration time was 4 d.     

Abscisic acid alleviates the deleterious effects of cold stress on ‘Sultana’ grapevine (Vitis vinifera L.) plants by improving the anti-oxidant activity and photosynthetic capacity of leaves

The effects of exogenous application of abscisic acid (ABA) on anti-oxidant enzyme activities and photosynthetic capacity in ‘Sultana’ grapevine (Vitis vinifera L.) were investigated under cold stress. When vines had an average of 15 leaves, 0 (control), 50, 100, or 200 µM ABA was sprayed to run-off on all leaves of each plant. Twenty-four hours after foliar spraying with ABA, half (n = 5) of the water-only control vines and half (n = 5) of each group of ABA-treated plants were subjected to 4°C for 12 h, followed by a recovery period of 3 d under greenhouse conditions (25°/18°C day/night). The remaining plants in each treatment group were kept at 24°C. Cold stress increased H₂O₂ and malondialdehyde (MDA) concentrations in vine leaves, whereas all foliar ABA treatments significantly reduced their levels. Chilled plants showed marked increases in their total soluble protein contents in response to each ABA treatment. ABA significantly increased the activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase in cold-stressed grapevine leaves. In contrast, cold stress markedly decreased the rates of leaf photosynthesis (A) and evaporation (E), stomatal conductance (g_s), and chlorophyll concentrations in leaves, but increased intercellular CO₂ concentrations (C_i) in leaves. Treatment with all concentrations of ABA resulted in lower leaf A, E, and g_s values, but higher C_i values at 24°C. However, following cold stress, ABA-treated vines showed higher leaf A, E, and g_s values, but lower C_i values compared to control vines without ABA treatment. The application of 50–200 µM ABA allowed chilled vines to recover more quickly when re-exposed to normal temperatures, enabling the vines to resume their photosynthetic capacity more efficiently following cold stress. These results showed that, by stimulating anti-oxidant enzyme systems and alleviating cold-induced stomatal limitations, ABA reduced the inhibitory effect of cold stress on the rate of CO₂ fixation in ‘Sultana’ grapevine plants.     

Nitric oxide alleviates adverse salt-induced effects by improving the photosynthetic performance and increasing the anti-oxidant capacity of eggplant (Solanum melongena L.)

Summary

Nitric oxide (NO) is an active molecule involved in many physiological functions in plants. To characterise the roles of NO in the tolerance of eggplant (Solanum melongena L.) to salt stress, the protective effects of exogenous sodium nitroprusside (SNP), a donor of NO, applied at different concentrations (0, 0.05, 0.1, or 0.2 mM), on plant biomass, photosynthesis, and anti-oxidant capacity were evaluated. The application of SNP alleviated the suppression of growth in eggplant under salt stress, as reflected by a higher accumulation of biomass. In parallel with growth, the application of SNP to salt-stressed plants resulted in enhanced photosynthetic parameters such as the net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), and intercellular CO₂ concentration (C_i), as well as an increased quantum efficiency of PSII (F_v/F_m), efficiency of excitation capture of open PSII centres (F_v’/F_m’), quantum yield of PSII ( _psii) and photochemical quenching coefficient (qP). Furthermore, exogenous SNP also reduced significantly the rate of production of O₂^{? –} radicals and the concentrations of malondialdehyde (MDA) and H₂O₂. It also increased the activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in eggplant leaves grown under salt stress. The results indicated that the protective effects of NO against salt stress in eggplant seedlings were most likely mediated through improvements in photosynthetic performance and the stimulation of anti-oxidant capacity.     

Hormonal regulation of physiological leaf spot and premature leaf abscission in ‘Golden Delicious’ apple trees

Exogenous growth substances (GA₄₊₇, IAA, PBA, and ABA) alone and in combination were applied as leaf dips to young ‘Golden Delicious’ apple trees in a growth room at 21 °C. All treatments containing GA₄₊₇ accelerated the incidence of physiological leaf spot over treatments without GA₄₊₇, ABA alone delayed the appearance of leaf spot. PBA, PBA + GA₄₊₇, and PBA + GA₄₊₇ + IAA retarded the abscission of spotted leaves.GA₄₊₇ and GA₄₊₇ + PBA also accelerated leaf spot development in bearing ‘Golden Delicious’ trees in the orchard.Fumigation of apple trees with ethylene at 2, 10, and 20 ppm had no influence on the occurrence of leaf spot or premature abscission.     

Effects of temperature and plant growth regulators on anthocyanin synthesis and phenylalanine ammonia-lyase activity in chicory (Cichorium intybus L.)

Summary

This study addresses the effects of air temperature and plant growth regulators on anthocyanin synthesis, sugar content and phenylalanine ammonia-lyase (PAL) activity in chicory (Cichorium intybus L.). Anthocyanin in chicory was synthesised at the highest level under 15°/10°C (day/night) temperatures, followed by 20°/15°C, and 25°/20°C; while synthesis was inhibited > 90% at 30°/25°C, resulting in an almost green colour. Sugar contents paralleled anthocyanin development under the same temperatures. The plant growth regulators, abscisic acid (ABA), ethephon and uniconazole all stimulated anthocyanin synthesis, with uniconazole treatment showing the greatest effect. Gibberellic acid (GA₃) inhibited anthocyanin development, while GA₃ in combination with uniconazole alleviated this inhibition.

PAL activity was higher at 15°/10°C or 20°/15°C (day/night) temperatures when plants were treated with ABA, ethephon or GA₃, than at 25°/20°C and 30°/25°C (day/night) temperatures. These results suggest that, under lower temperatures, plant growth regulators may play an important role in anthocyanin synthesis and PAL activity in chicory.     

Moving lamps increase leaf photosynthetic capacity but not the growth of potted gerbera

To investigate the responses of leaf photosynthesis and plant growth to a moving lighting system, potted gerberas (Gerbera jamesonii H. Bolus ex J.D. Hook “Festival”) were grown under supplemental lighting in a greenhouse with either a stationary or a moving lighting system positioned above the benches. The stationary system consisted of a fixed high pressure sodium (HPS) lighting system, while the moving lighting system consisted of a moving HPS fixture attached to a cable system to move the light fixture back and forth over the crop. In both cases, the supplemental lighting was applied from 6:00 to 24:00 h with the same supplemental daily light integral (4.9 mol m⁻² day⁻¹). Moving lamps significantly increased leaf photosynthetic capacity as represented by light saturated net CO₂ exchange rate (NCER) (A_sat), light- and CO₂-saturated rate of NCER (A_max), maximum rate of Rubisco carboxylation (V_cmax), maximum rate of electron transport (J_max) and rate of triose phosphate utilization. However, in situ leaf NCER and stomatal conductance, leaf chlorophyll content index, leaf area, leaf thickness, fresh weight of plants were significantly lower under moving lighting than under stationary lighting. It is suggested that the reduced growth of plants under moving lighting might be due to (1) the overall lower light use efficiency of leaves under moving lighting than those under stationary lighting; (2) the slower response time of the photosynthetic system compared to the rate of change in light intensity under moving lighting.     

Sana Physiological responses of two grapevine (Vitis vinifera L.) cultivars to CycocelTM treatment during drought

The plant growth regulator Cycocel^TM [(2-chloroethyl)trimethylammonium chloride] can be used to produce drought tolerance in grapevine (Vitis vinifera L.) due to a reduction in the ratio between vegetative growth and fruit production. To evaluate the physiological responses of two grapevine cultivars to drought and Cycocel^TM treatment, a factorial experiment was conducted in a greenhouse. The factors included irrigation frequency (at 5-, 10-, or 15-day intervals corresponding to no, mild, or severe drought stress), Cycocel^TM concentration (0, 500, or 1000 mg l^–1), and cultivar (‘Rasheh’ or ‘Bidane-Sefid’). Stomatal conductance (g_s) the net rate of CO₂ assimilation (A_net), the rate of transpiration (T_r), and chlorophyll a and b concentrations decreased in plants exposed to mild or severe water-deficit stress, whereas carotenoid, proline, and total soluble sugar concentrations increased compared to plants with no drought stress. The relative water content (RWC) of leaves declined only under severe drought stress. A reduction in intercellular CO₂ concentrations (C_i) occurred under mild drought stress; however, under severe drought stress, C_i values increased. Under mild drought stress, the reduction in the net rate of photosynthesis was related to stomatal closure, whereas under severe drought stress, non-stomatal factors were dominant. Water-use efficiency (WUE) improved under mild drought stress relative to non-stressed plants, but under severe drought, it declined. Foliar applications of Cycocel^TM resulted in increased A_net, g_s, T_r, and WUE values, as well as proline and soluble sugar concentrations. ‘Rasheh’ was more tolerant to drought stress than was ‘Bidane-Sefid’. Foliar applications of Cycocel^TM, particularly at 1000 mg l^–1, mitigated the negative effects of drought stress by increasing A_net, WUE, RWC, compatible solute concentrations, such as proline, soluble sugar, and chlorophyll a and b concentrations.     

Effects of Gibberellic Acid and Temperature on the Growth of Young Seedlings of Syringa Vulgaris L.

The application of gibberellic acid (0, 5, 20 and 80 µg) to seedlings of Syringa vulgaris L. about two weeks after germination increased significantly the total length, the length of internodes and the dry weight (d.w.) of shoots and the net assimilation rate. GA₃ also had a small but significant positive effect on the number of pairs of leaves, especially at high temperatures; it increased the girth, but this effect was not significant.

GA₃ reduced significantly the d.w. of roots and leaves but did not affect the leaf/root ratio. GA₃ had no effect on the total plant d.w. or the relative growth rate.

The effect of GA₃ on shoot growth was dependent on temperature and on the stage of growth. One and two weeks after its application it had the maximum relative effect at high temperatures (21–24 °C) but at the end of the experiment (8.5 weeks) the maximum effect was reached at 12 °C; it decreased with increasing temperature and was not significant at 24 °C. By this stage there were, however, no statistical interactions between temperature and GA₃ for total length and for d.w. of shoots, roots, leaves and of the whole plant.

Increasing temperatures over the range 12–24 °C resulted in increases in the following characteristics: the number of pairs of leaves; length of internodes, diameter and total length of the shoot; the d.w. of shoots, roots, leaves and of the whole plant; the d.w. ratios of leaves/roots and shoots/roots; and the relative growth rate and net assimilation rate. High temperatures reduced the root/whole plant dry weight ratio. The effect of temperature on the number of pairs of leaves was linear, and results at alternating temperatures (24°/18° and 21°/15 °C, 8 hr/16 hr) did not deviate significantly from values expected on the basis of mean daily temperature.     

Low temperature and gibberellic acid stimulation of germination in Sambucus caerulea Raf

Sambucus caerulea (elder) seeds did not germinate after 4°C cool treatments for up to 30 days, when monitored for a further 30 days at 21°C. When seeds were soaked for 24 h in gibberellic acid (GA₃) prior to and during cold treatment, germination percentage depended on GA₃ concentration and duration of cold treatment. The highest germination percentage was 55 (1000 mg l⁻¹ GA₃ for 30 days at 4°C). When seeds were treated with ethephon at 0, 100 or 1000 mg l⁻¹, no germination was recorded after a subsequent 30-day 4°C treatment. Ethephon added to GA₃ gave a strong interaction, leading to further promotion in germination. Optimal germination was obtained after 1000 mg l⁻¹ GA₃ and 100 mg l⁻¹ ethephon for 30 days at 4°C (69%).The addition of ethanol, acetone, dimethyl sulfoxide or polyethylene glycol to the GA₃ soak as infusion agents either reduced or did not change the germination percentage.     

GA3处理对采后竹笋木质化及内源激素水平的影响

 研究了外源GA₃ 浸泡处理对采后竹笋木质化的生理生化变化及内源激素水平的影响。结果表明: 竹笋贮藏期间, 苯丙氨酸解氨酶(PAL) 、肉桂酸- 4 - 羟化酶(C4H) 和过氧化物酶( POD) 活性先增加后减少, 木质素含量和组织硬度逐渐增加, 而可食用率逐渐下降, GA₃ 和IAA含量逐渐减少, ABA含量先增加后减少。PAL、C₄H和POD活性与ABA /GA₃ 的比值呈正相关。外源GA₃ 处理能增加内源GA₃ 含量, 降低ABA /GA₃ 的比值, 并抑制PAL、C4H和POD活性的上升, 降低木质素含量和硬度, 提高可食用率, 从而延缓竹笋木质化进程。推测外源GA₃ 处理可能通过降低ABA /GA₃ 的比值来延缓竹笋木质化进程。     

Root restriction-induced limitation to photosynthesis in tomato (Lycopersicon esculentum Mill.) leaves

Root restriction often depresses photosynthetic capacity and the mechanism for this reduction, however, remains unclear. To identify the mechanism by which root restriction affects the photosynthetic characteristics, tomato (Lycopersicon esculentum Mill.) seedlings were subjected to root restriction stress with or without supplemental aeration to the nutrient solution. With the development of the root restriction stress, CO₂ assimilation rate was decreased only in confined plants without supplemental aeration. There were also significant decreases in leaf water potential, stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and increases in the stomatal limitation (l) and the xylem sap ABA concentration. Meanwhile, the maximum carboxylation rate of Rubisco (V_cmax) and the capacity for ribulose-1,5-bisphosphate regeneration (J_max) also decreased, followed by substantial reductions in the quantum yield of PSII electron transport (Φ_PSII). Additionally, root restriction resulted in accumulation of carbohydrates in various plant tissues irrespective of aeration conditions. It is likely that root restriction-induced depression of photosynthesis was mimicked by water stress.     

Silicon promotes seedling growth and alters endogenous IAA,GA3 and ABA concentrations in Glycyrrhiza uralensis under 100 mM NaCl stress

A sand culture experiment was conducted to determine the effects of Si on the growth and endogenous hormone concentrations (indole-3-acetic acid [IAA], gibberellic acid [GA₃], and abscisic acid [ABA]) in Glycyrrhiza uralensis seedlings under 100 mM NaCl stress. Si time-dependently improved the growth and increased the biomass of seedlings, and the effect was greater at 20 days than that at 10 days after Si treatment. The effects of Si on the growth parameters and biomass were dependent on Si concentration, that is, these parameters increased with increasing Si concentration. Si also increased the levels of endogenous hormones in G. uralensis seedlings in a concentration-dependent manner. The effects on IAA and GA₃ increased with increasing Si concentrations, and the effect on ABA was higher at 2 mM Si than that at the other Si concentrations. Furthermore, the effects of Si on IAA and GA₃ were greater at 10 days than those at 20 days after the treatment, whereas the effect on ABA was greater at 20 days than that at 10 days after the treatment. Hence, Si can regulate the concentrations of endogenous hormones and correspondingly improve the growth of G. uralensis seedlings under salt stress condition.     

Factors affecting the response of tulips to gibberellin

Gibberellic acid (GA₃) treatment of forced tulip crops has potential for producing faster growth to anthesis in the glasshouse, for reducing losses due to floral bud blasting, and for reducing the duration of cold storage needed to obtain satisfactory flowers. Using partly and fully cooled direct-forced tulips, cultivar ‘Apeldoorn’, several factors (relevant to the definition of GA₃ treatments) were studied. Experiments confirmed the previously recorded effects of gibberellins in tulips: GA₃ injections reduced the duration of the glasshouse period, enhanced flower survival and flower length, and reduced stem length at flowering.Following bulb storage at temperatures from ?2 to 20°C, GA₃ reduced the glasshouse period by 15–25% and increased flower length, compared to controls, irrespective of storage temperature. Stem length was also reduced by GA₃, this effect being greater following a storage temperature of 5°C or lower. When GA₃ was applied during the period of 17°C-storage which precedes cool storage, or during or after storage at 5°C, it was found that treatments during or at the end of cool storage were more effective in producing the characteristic effects of GA₃ than were pre-cooling applications. In partly cooled bulbs (but not fully cooled ones), the GA₃-induced earliness of flowering was about doubled when GA₃ injections were given repeatedly at 2-week intervals throughout storage. The responses to GA₃ injections were found to be unmodified by early-lifting and heat-treatment (for earlier forcing), by delaying the start of 5°C storage (for later forcing), by glasshouse temperature (16 and 18°C), and by shading treatments; there was little effect of bulb size.     

Effect of stratification-temperature,chemical treatments and seed coat on the growth of peach seedlings cultivar ‘Sharbati’

In order to obtain normal seedlings of peach cultivar ‘Sharbati’ before the commencement of winter, treatments with GA₃, thiourea and kinetin were given to seeds before stratification at 7°C, 10°C or 24°C. The seedlings raised from the treated seeds and after-ripened at 24°C were dwarf. The seedling growth was increased when the treated seeds were stratified at 10°C or 7°C and the stratification period was prolonged from 15 days to 75 days. 10°C stratification-temperature was better than 7°C. The seedling growth was improved when the seed coat was removed before the treatments. With respect to both seed types, 1000 mg/l GA₃ produced the tallest seedlings at all the after-ripening temperatures and during each stratification period. The next best treatment was 100 mg/l kinetin.     

Foliar Spray with Different Agrochemicals on Fruit Quality and Exportability of ‘Washington’ Navel Orange Fruit (Citrus sinensis L.)

The present study was carried out to improve fruit set, yield, quality, marketability, and exportability of ‘Washington’ Navel orange. Pre-harvest foliar sprays of GA₃, K, and Ca, either alone or combined, were applied at full bloom. The following treatments were applied: {control (T₁), 25 mg/L GA₃ (T₂), 2% K₂SO₄ (T₃), 25 mg/L GA₃ + 2% K₂SO₄ (T₄), 25 mg/L GA₃ + 2% Ca Cl₂ (T₅), 2% K₂SO₄ + 2% Ca Cl₂ (T₆), and 25 mg/L GA₃ + 2% K₂SO₄ + 2% Ca Cl₂ (T₇). All treatments improved fruit set, yield, physical and chemical characteristics, mineral content of leaves and fruit rind, and the percentage of exportable fruit in comparison to the control. Fruit set, fruit detachment force, peel firmness, and the mineral content of leaves and fruit rind were enhanced significantly with the combination of GA₃ + K₂SO₄ + Ca Cl₂ (T₇) in comparison to all other treatments and the control. Results indicated that all foliar combination treatments improved fruit quality and marketability, and increased the percentage of exportable fruit and reduced the defects of non-exportable fruit.     

Effects of growth regulators on growth and flowering in Hippeastrum hybridum hort

Soaking of bulbs in 3 concentrations of indoleacetic acid (IAA), gibberellic acid (GA₃), 2-chloroethyltrimethyl ammonium chloride (cycocel) or 2-chloroethylphosphonic acid (ethrel) showed various responses on growth and flowering. IAA increased the weight and number of bulblets, GA₃ increased bulb weight. Cycocel (1000 mg l^?1) increased the number of flowers, while GA₃ increased the diameter of the flowers.Application of IAA at 100 mg l^?1 and GA₃ at 10, 100 or 1000 mg l^?1 twice as foliar spray at an interval of 30 days promoted the number of bulblets on the treated plants, while high concentrations of cycocel and ethrel (1000 mg l^?1) increased the weight of bulblets. All concentrations of IAA, GA₃ and 1000 mg l^?1 cycocel increased the number and size of the flowers.     

Gas-exchange responses of rose plants to CO2 enrichment and light

Summary

This paper describes the response of gas exchange rates and water use efficiency of rose plants, by means of the characterization in situ and the analysis of the response of photosynthesis, transpiration and water use efficiency of whole plants to CO₂ enrichment under the irradiance conditions prevailing in greenhouses of southern France. Net CO₂ assimilation (A_n) and transpiration (E) of whole rose plants (Rosa hybrida, cv. Sonia) were measured during winter and spring periods. The response of A_n to light and CO₂ were fitted to a double hyperbola function (r² = 0.84). Maximum net assimilation rate (A_nmax), light and CO₂ utilization efficiencies (α₁, α_c) as well as light and CO₂ compensation points (Γ₁ , Γ_c) were calculated for the whole plant and compared with leaf and canopy data in the literature. The whole-plant characteristics generally had values intermediate between those related to leaf and canopy. Light saturation at sub-ambient air CO₂ concentration (C_a) was reached for relatively low PFFD values (300 µmol m^?2 s^?1), whereas at ambient and enriched C_a light saturation occurs for PPFD ≈ 1000 µmol m^?2 s^?1. Doubling C_a from 350 to 700 µmol mol^?1 increased A_nmax and α₁ by respectively 40% and 30%, while reducing Γ₁ by 27%. A threefold increase of C_a from 350 to 1050 µmol mol^?1 induced a reduction of 20% of E. Instantaneous transpirational water use efficiency, WUE (=A_n/E), is relatively insensitive to PPFD, although a slight decrease with PPFD is observed at high CO₂ concentration, but shows marked variations with C_a and leaf to air vapour pressure defiçit (D₁). Increase of C_a from 350 to 1000 µmol mol^?1 gave about 50% increase in WUE. Increase of D₁ from 0 to 2 kPa induced 30% decrease in WUE at ambient C_a and 50% decrease at 1000 µmol mol^?1.     

Substitution of the cold requirement of tulip CV. ‘apeldoorn’ by GA3

To investigate whether GA₃ can substitute for the requirement, 1 mg GA₃ was injected in dry stored bulbs before, during or after the following treatments: (a) 12 weeks at 21°C, (b) 12 weeks at 5°C, (c) 6 weeks at 21°C followed by 6 weeks at 5°C, and (d) 6 weeks at 5°C followed by 6 weeks at 21°C. The bulbs were then planted in light at 15°C. Plants from bulbs previously subjected to (d) flowered earlier than bulbs from treatments (a) and (c) but later than those subjected to (b). Both the GA₃ and the 5°C treatments shortened the time from planting until flowering; however, GA₃ produced shorter plants and induced the formation of parthenocarpic fruits. Reduction of scape length by GA₃ was less when it was given at a later time during treatments (a) and (c) whereas the scape lengths of bulbs subjected to treatments (b) and (d) were hardly affected by the time chosen for GA₃ application.     

Effects of air temperature,soil temperature and soil moisture on growth and development of tomato itself and grafted on its own and egg-plant rootstock

The problem was studied whether tomatoes, grown in a hot and arid climate, benefit from grafting on egg-plant, which is highly efficient in water uptake. Growth and development of tomato (T), tomato grafted on its own rootstock ($\text{T}\text{T}$) and tomato grafted on egg-plant rootstock ($\text{T}\text{E}$) were compared at air temperatures of 28°C during the day and 18°C during the night ($\text{28}\text{18}$) and at 28°C constantly ($\text{28}\text{28}$), at soil temperatures of 14, 21 and 28°C with the following soil moisture regimes: wet (W₁), medium (W₂) and dry (W₃).At $\text{28}\text{18}$ and $\text{28}\text{28}$ water consumption was about equal, but the transpiration ratio at $\text{28}\text{28}$ was twice as high as that at $\text{28}\text{18}$. The latter conditions gave a much stronger plant with more fruits. At a soil temperature of 14°C water use was strongly reduced. The transpiration ratio increased with the soil temperature. Differences in plant type were small. At the highest soil temperature of 28°C fruit growth was strongly reduced. At lower soil moisture levels less water was used and the transpiration was lower. Plant type was correlated herewith.Vegetative growth of $\text{T}\text{T}$ was weaker than of T, but generative growth was stimulated. The strong E rootstock stimulated vegetative growth at high air and soil temperature, but fruit growth was very poor under these conditions; at a low soil temperature of 14°C vegetative growth was also reduced.The hope that the E rootstock would be beneficial for fruit growth at high temperatures was not fulfilled.An additional experiment in a growth-room at 23°C showed that under conditions of moisture stress there was no difference in water potential between leaves of $\text{T}\text{T}$ and $\text{T}\text{E}$.