Effects of day and night temperature on photosynthesis,antioxidant enzyme activities,and endogenous hormones in tomato leaves during the flowering stage

To study the effects of day and night temperature difference (DIF) on tomato growth, a controlled experiment using Solanum lycopersicum L., cv. Jinguan 5 was conducted. The daily mean temperature (T_m) was maintained at 18°C and 25°C, and the DIF was set at 0°C, 6°C, and 12°C. The results indicated that chlorophyll a (Chl a) and chlorophyll b (Chl b) gradually increased as DIF rose. At 18°C T_m, the carotenoid content reached a maximum at 12°C DIF. The Chl a/Chl b, net photosynthetic rate (P_N), photosynthetic rate at irradiation saturation (P_max), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), stomatal limitation value, the maximum assimilation rate (A_max), apparent quantum efficiency (A_q), carboxylation efficiency (C_e), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), gibberellin A₃ (GA₃), and indole-3-acetic acid (IAA) were highest, while malondialdehyde (MDA) was lowest at 6°C DIF. At 25°C T_m, P_N, P_max, A_max, A_q, C_e, g_s, C_i, CAT, POD, GA₃, IAA, and zeatin reached the maximum under 6°C DIF, while SOD and MDA reached the maximum under 12°C DIF. Furthermore, the morphological index peaked at 6°C DIF under 18°C and 25°C T_m. The results suggested that 6°C DIF improved the growth and development of tomato during the flowering stage. ABBREVIATIONS: Aq – apparent quantum efficiency; Amax – the maximum assimilation rate; CAT – Catalase; Chl a(b) – chlorophyll a(b); Ca – ambient CO₂ concentration; Ce – carboxylation efficiency; Ci – intercellular CO₂ concentration; DIF – difference between day temperature (TD) and night temperature(TN); FM – fresh mass; gs – stomatal conductance; GA₃ – gibberellin A₃; IAA – indole-3-acetic acid; Ls – stomatal limitation value; MDA – malondialdehyde; Pmax – photosynthetic rate at irradiation saturation; PN – net photosynthetic rate; POD – peroxidase; ROS – reactive oxygen species; SOD – superoxidedismutase; Tm – daily mean temperature; ZT – zeatin.     

Some physiological changes in strawberry (Fragaria × ananassa ‘Camarosa’) plants under heat stress

Summary

The effects of heat injury induced by long exposures were evaluated in strawberry (Fragaria × ananassa ‘plants’) Camarosa in this study. Seedlings were grown in 14 × 12 cm pots using perlite for three weeks at 25/10°C day/night temperature, and watered daily by modified 1/3 Hoagland nutrient solution. Half of the plants were transferred to a growth chamber with a constant 25°C, 16/8 h (light/dark) photoperiod regime and 1200 lux light intensity for a week to acclimate the plants. Temperature was increased stepwise (5 K per 48 h) to 30, 35, 40°C and finally to 45°C. In addition to others, plants were transferred from the outside to the growth chamber, at each temperature step to impose a heat shock. Leaf relative water content (RWC, %), loss of turgidity, chlorophyll content (Spad value) and heat-stress tolerance (HTS; LT₅₀) were measured in control and stressed plants. Total soluble proteins and total DNA were extracted from the leaves following the above treatments using standard procedures and total protein contents were determined using a Bradford assay. In general, effects of gradual heat stress (GHS) and shock heat stress (SHS) on the variables studied were mostly significant, except for chlorophyll content, while the effect of temperatures was significant for all the variables. Interaction between the heat stress type and temperature treatments was not significant for leaf RWC, loss of turgidity and chlorophyll content. Data also indicated that total protein and DNA contents were changed significantly by heat stress types (GHS and SHS) and/or temperature treatments. The plants exposed to GHS exhibited a significant increase in HST compared with the plants exposed to SHS (LT₅₀ of 41.5°C and 39°C, respectively). Consequently, gradual heat stress increased HST in strawberry leaves. Increased HST may be associated with the accumulation of several heat-stable proteins in GHS plants.     

高温胁迫对孔雀草和万寿菊不同品种生长和生理的影响

以万寿菊属（Tagetes）的6个孔雀草品种和3个万寿菊品种为试材,研究了38℃／21℃（昼／夜）高温胁迫对其株高、根长、根数、干样质量、热害指数以及叶绿素[Chl．（a＋b）]含量、叶片相对电导率（REC）、丙二醛（MDA）含量、叶片相对含水量（RWC）、抗氧化酶（SOD、POD、CAT、APX）活性等指标的影响。结...     

Cover Crops For Fruit Plantations: V. Effect of Form and Time of Application of Nitrogen on Orchard Swards

Summary

The effects of storage temperature on quality and physiological responses in Chinese bayberry fruit (Myrica rubra Sieb. and Zucc. cv. Wumei) were investigated. Freshly harvested bayberries were stored at 20°C, 10°C, or 1°C for 60 h, 5 d, or 14 d, respectively. The rates of respiration and ethylene production, fruit firmness, total sugars, organic acids, and total soluble solids (TSS) contents, total titratable acidity (TA), pH, relative electrical conductivity (REC), and polyphenol oxidase (PPO) activity of fruit were measured during storage. The results showed that the rates of respiration and ethylene production decreased during storage, and that their values were lowered significantly by decreasing the storage temperature. Low temperatures maintained higher TSS contents, TA, and fruit firmness and inhibited any increases in pH, REC, and PPO activity in bayberry fruit. There was a significant decline in citric acid and sucrose contents during storage, with a more rapid decrease occurring at higher temperatures. The data obtained indicate that cold storage is an effective way to maintain quality and chemical components in Chinese bayberry fruit.     

Root shoot interactions in passionfruit (Passiflora sp.) under the influence of changing root volumes and soil temperatures

Summary

Passionfruit are grown in the tropics and subtropics where mean monthly soil temperatures at 15 cm range from about 10° to 30°C. The choice of rootstock can also influence production with most industries exploiting either the purple (Passiflora edulis f. edulis) or golden passionfruit (P. edulis tflavicarpa). We examined the relationship between shoot and root growth in purple x golden hybrid E-23 grafted onto golden passionfruit seedlings. Growth was manipulated by varying the volume of the soil available to the roots or temperature of the root zone. Shoot and root growth increased as root zone volume increased from 0.3, 1.4, 4, 12 to 24 1. Shoot weight (W_s) was correlated with root weight (W_R):W_S = 12.697 + 5.272 W_R + 0.195 W_R² (r² = 91%, P<0.001), with the plants allocating a smaller proportion of dry matter to the roots as root weight increased. Differences in shoot growth with pot volume were not due to changes in water or nutrient status. In the temperature experiment, the two critical root zone temperatures at 90% of maximum growth were about 20° and 35° C for vine extension, leaf area, node and leaf production, and 20° and 30°C for flower production. Leaf and stem dry weight were optimal between about 18° and 34°C, while maximum root growth occurred at 38°C. There was a weak relationship between shoot (W_s) and root dry weight (W_R): W_s = ?19.346 + 24.500 W_R ?1.046 W_R² (r² = 53%, .P<0.001). Apparently, variations in shoot growth at different soil temperatures cannot be explained solely by differences in root growth. Reduced growth at 10°C was associated with lower chlorophyll concentration, stomatal conductance and net CO₂ assimilation, but not lower leaf water potential. The concentration of most nutrients were lower at 10°C than at higher temperatures, but none was outside the range which would be expected to restrict growth. There appears to be a co-ordination of shoot and root growth as the soil volume available for root growth increases, whereas root temperature affects the roots and tops differently. The results of the pot volume experiment demonstrate the importance of rootstock vigour in passionfruit breeding. Productivity would be affected in cool subtropical areas with soil <20°C and in tropical areas with soil >30°C.     

Stock-Scion Incompatibility in Citrus and its Cause

Summary

The effects of 75 mM and 150 mM NaCl (EC 8.50 and 15.35 dS m^–1) were studied on a salt-tolerant and a salt-sensitive pepper (Capsicum annuum L.) genotype. The salt-tolerant genotype showed lower declines in relative water content (RWC), no change in chlorophyll (Chl) content, lower increases in lipid peroxidation, and greater increases in superoxide dismutase (SOD) activity, total protein content, and glutathione content. The salt-sensitive genotype showed greater decreases in RWC, Chl content, SOD activity, and in guaiacol peroxidase (GPOX) activity, and higher increases in lipid perxidation and the amount of proline, with a negligible increase in glutathione content.These results revealed that increases occurred in some anti-oxidative stress enzymes in the salt-tolerant pepper genotype, as well as increases in glutathione content under salinity stress. These may provide better protection against reactive oxygen species (ROS).     

Effects of proline on antioxidant system in leaves of grapevine (Vitis vinifera L.) exposed to oxidative stress by H2O2

Although proline is one of the major computable organic solutes that accumulate in many plant species in abiotic stresses, a hot debate continues about whether proline accumulation is a reaction to abiotic stress, or a plant's response is associated with stress tolerance. The effects of proline on antioxidative system in grape leaves of Vitis vinifera L. cv., ‘Öküzgözü’ exposed to oxidative stress by H₂O₂ was investigated. Endogenous proline, hydrogen peroxide (H₂O₂), malondialdehyde (MDA) concentrations, percentage of electrolyte leakage (EL), and some of the antioxidant enzyme activities; such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (POD) were measured spectrophotometrically. Inhibitory effect of H₂O₂ on antioxidant enzyme activities, MDA, and EL was found. In the presence of proline, SOD and CAT activities decreased, while POD and APX activities increased. Proline pre-treatment resulted in a decrease in cellular H₂O₂ content, MDA, and EL, while cellular concentration of proline increased. Based on the finding, it was suggested that proline and H₂O₂ could play an important role in oxidative stress injury of grapevine leaves grown in vitro culture. Also, proline might have a direct positive effect on antioxidant enzyme system, membrane phase change, MDA, and EL.     

低温胁迫后增温对‘索邦’百合生理活性的影响

以百合品种‘索邦’为试材,以室温(昼/夜温度22℃/14℃)为对照(CK),通过人工气候室模拟低温环境(昼/夜温度8℃/2℃)对其胁迫处理3、7、10 d,随后立即增至室温,采用氮蓝四唑(NBT)光化还原法等常规方法测定其超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、相对电导率(REC)、脯氨酸(Pro)及可溶性糖的含量,探讨低温胁迫后增温对百合10叶期、20叶期及现蕾期生理活性的影响,以期为冬季日光温室的调温及切花百合的种植管理提供技术参考。结果表明:与CK相比,低温胁迫后各生长期百合叶片SOD活性、POD活性、CAT活性、相对电导率(REC)、脯氨酸(Pro)及可溶性糖含量均随胁迫时间的延长不断升高,胁迫10 d后分别达到各期CK的0.97~2.33、2.05~5.26、1.84~2.14、2.40~2.49、0.87~1.87、1.77~5.33倍,增温处理后其SOD活性、POD活性、CAT活性、REC、Pro以及可溶性糖含量均随处理时间的延长不断降低,增温10 d后趋于各处理,分别为CK的1.03~1.26、1.12~2.18、1.02~1.12、1.35~1.72、0.87~1.03、0.56~1.32倍。在整个处理过程中,百合叶片抗氧化酶(SOD、POD、CAT)活性、相对电导率及可溶性糖含量随温度变化最为明显,且低温胁迫后增温可缓解‘索邦’百合不同生长期所遭受的生理伤害。     

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.     

Using Allium alien monosomic addition lines to study chlorophyll degradation in stored Japanese bunching onion

Summary

Chlorophyll (Chl) degradation and the formation of Chl derivatives in stored leaves of Japanese bunching onion (JBO; Allium fistulosum L., genome FF) were determined to elucidate the mechanism of Chl degradation by using alien monosomic addition lines (AMALs; FF+1A to FF+8A) of JBO from shallot (A. cepa L. Aggregatum group, genome AA). Year-round changes in Chl content in JBO and in the AMALs were also detected over 2 years. The Chl content in FF was significantly influenced by the alien chromosomes from shallot. In particular, the Chl contents of FF+4A or FF+5A, were higher in Winter than in FF, which suggests that chromosomes 4A and 5A from shallot had a larger influence on the formation of Chl than the other chromosomes. Chl contents in FF+3A and FF+5A decreased greatly in the leaves of AMALs and JBO during storage at 25°C, whereas in FF+4A the Chl content was the lowest compared to the control, FF. Chlorophyllide (Chlide) a, C13²-hydroxychlorophyll (OHChl) a, pheophorbide a, and pheophytin (Phy) a, as derivatives of Chl a, were present mainly during storage of JBO and the AMALs. Phy alevels increased with Chl degradation, especially in FF+3A, while OHChl alevels in FF and FF+3A showed a decline during storage. In addition, Chlide alevels in all lines diminished during storage.Thus, Chl amay be degraded, in part, through Phy a, as well as Chlide aand OHChl a, in JBO and the AMALs during storage.     

Floral induction in tropical fruit trees: Effects of temperature and water supply

Summary

Floral induction in tropical trees generally follows a check in vegetative growth. However, it is not easy to identify the environmental factors involved in flowering, which normally occurs during the dry season when temperatures are also often lower. The separate and combined effects of temperature and water supply on floral induction were investigated in ‘Hass’ avocado (Persea americana), ‘Lisbon’ lemon (Citrus limon). ‘Wai Chee’ litchi (Litchi chinensis) and ‘Sensation’ mango (Mangifera indica). Low temperatures (15°/10°C or 15°/10°C and 20°/15°C compared with 30°/25°C and 25°/20°C) generally decreased vegetative growth and induced flowering in well-watered avocado, litchi and mango. A pre-dawn leaf water potential (ψ_L) of ?1.7 to ?3.5 MPa compared with ?0.4 to ?0.7 MPa in control avocado and litchi, and a pre-dawn relative water content (R.W.C.) of 90-93% compared with 97% or above in control mango plants also reduced or eliminated vegetative growth, but did not induce flowering. Low temperatures (15°/10°C compared with 20°/5°C, 25°/20°C or 30°/25°C) and water stress (pre-dawn ψ_L of ?2.0 to ?3.5 MPa compared with ?0.7 to ?0.8 MPa in controls) reduced or eliminated vegetative growth in lemon. In contrast to the response in avocado, litchi and mango, flowering in lemon was very weak in the absence of water stress at 15°/10°C or outdoors in Brisbane in subtropical Australia (Lat. 28°S), and was greatest after a period of water stress. The number of flowers increased with the severity and duration of water stress (two, four or eight weeks) and was generally greater after constant rather than with cyclic water stress. In lemon and litchi, net photosynthesis declined with increasing water stress reaching zero with a midday ψ_L of ?3.5 to ?4.0 MPa. This decline in carbon assimilation appeared to be almost entirely due to stomatal closure. Despite the reduction in midday CO₂ assimilation, starch concentration increased during water stress, especially in the branches, trunk and roots of lemon. Leaf starch was uniformly low. The number of flowers per tree in lemon was strongly correlated with starch in the branches (r²=77%, P<0.01) and roots (r²=74%, P<0.001). In litchi, starch was lower than in lemon roots and was not related to flowering.

In separate experiments to test the interaction between temperature and water supply, low day/night temperatures (23°/18° and 18°/15°C compared with 29°/25°C) reduced vegetative growth and induced flowering in avocado, litchi and mango. None of these species flowered at 29°/25°C or as a result of water stress (ψ_L of ?1.5 MPa compared with ?0.3 MPa for avocado and ?2.0 MPa compared with ?0.5 MPa for litchi, and R.W.C, of 90-93% compared with 95-96% in mango). In contrast, in lemon, flowering was very weak (<10 flowers per tree) in the absence of water stress (pre-dawn ψ_L of ?2.0 MPa compared with ?0.5 MPa) and was only heavy (>35 flowers per tree) after stressed trees were rewatered. There were slightly more flowers at 18°/15°C than at 23°/18° and 29°/25°C in control plants, but no effect of temperature in stressed plants. Starch concentration in the roots of avocado, lemon, litchi and mango was generally higher at 18°/15°C and 23°/18°C than at 29°/25°C. Water stress increased the starch concentration in the roots of lemon and litchi and decreased it in avocado. There was no effect in mango. There was a weak relation (r²=57%, P<0.05) between the number of flowers per tree in lemon and the concentration of starch in the roots. In contrast, there was no significant relationship between flowering and starch levels under the various temperature and water regimes in the other species. In another experiment, only vegetative growth in litchi and mango occurred at 30°/25°C and only flowering at 15°/10°C. Six weeks of water stress (pre-dawn ψ_L of ?2.5 MPa compared with ?1.0 MPa or higher in litchi, and R.W.C, of 90-93% compared with 95% or higher in mango) in a heated glasshouse (30°C days/20°C night minimum) before these temperature treatments did not induce flowering.

Temperatures below 25°C for avocado and below 20°C for litchi and mango are essential for flowering and cannot be replaced by water stress. The control of flowering in lemon over the range of day temperatures from 18°C to 30°C differed from that of the other species in being mainly determined by water stress. Flowering was generally weak in well-watered plants even with days at 18°C. Starch did not appear to control flowering.     

Regulation of some biochemical attributes in drought-stressed cauliflower (Brassica oleracea L.) by seed pre-treatment with ascorbic acid

Cauliflower (Brassica oleracea L. var. botrytis) is widely used as a vegetable in many countries; however, productivity is adversely affected in areas affected by drought. To investigate the role of exogenously applied ascorbic acid (AsA) in mitigating the negative effects of drought on cauliflower, a pot experiment was performed using two cultivars of cauliflower ‘Local’ and ‘S-78’. Seeds of both cultivars were soaked in 75 mg l^–1, or in 150 mg l^–1 AsA, or in water (control) for 16 h. Water-deficit stress suppressed plant growth, reduced leaf chlorophyll concentrations, relative water contents (RWC), shoot and root P and K⁺ ion concentrations, and total soluble protein concentrations, significantly. However, significant drought-induced increases were observed in relative membrane permeability (RMP), the accumulation of total phenolic compounds, leaf free proline, glycinebetaine (GB), endogenous AsA, and hydrogen peroxide concentrations, and in the activity of superoxide dismutase (SOD). Seed treatment with 75 or 150 mg l^–1 AsA resulted in lower accumulations of H₂O₂, while increasing shoot and root fresh weights and dry weights, RWC, total phenolic compound, free proline, GB, and endogenous AsA concentrations, and the activities of SOD and catalase (CAT). No changes were observed in leaf chlorophyll concentrations or in peroxidase (POD) activities, RMP, shoot and root P and K⁺ ion accumulation, or in total soluble protein concentrations under water stress or non-stress conditions following seed treatment with AsA. ‘Local’ had higher proline concentrations and SOD activities; however, ‘S-78’ had higher RWC values, GB, and AsA concentrations. Overall, a pre-sowing treatment of cauliflower seed with 75 or 150 mg l^–1 AsA improved seedling tolerance to drought stress in both cultivars, which could be attributed to AsA-induced decreases in RMP and H₂O₂ concentrations, increases in the activities of CAT and SOD, increased RWC, and higher total phenolic compound, proline, GB, and AsA concentrations. The exogenous application of AsA therefore offers an effective strategy to minimise the adverse effects of drought stress on vegetable crops, including cauliflower.     

Effect of methyl jasmonate on reactive oxygen species,antioxidant systems,and microstructure of Chinese winter jujube at two major ripening stages during shelf life

The effect of post-harvest application of methyl jasmonate (MeJ) on reactive oxygen species, antioxidant systems, and cellular structure in Chinese winter jujube (Ziziphus Jujuba Mill.) at the major ripening stages of green maturity (GM) and half-red maturity (HM) were investigated. Jujube fruit at each ripening stage were treated with 0, 50, 100, and 200?μmol?l^?1 MeJ for 24 h, then stored at 20 ± 2°C for shelf-life testing. Thereafter, changes in firmness, color, respiration rate, superoxide anion (O₂^?), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), ascorbic acid (AsA), and glutathione (GSH) were measured at 4-d intervals for up to 8 d. Results showed that, in comparison with control fruit, MeJ treatment effectively suppressed the decrease of firmness, color, and respiration rate, inhibited the production of O₂^? and accumulation of H₂O₂ and MDA, maintained higher activities of SOD and CAT and contents of AsA and GSH, and preserved the integrity of cell membranes and organelles. The degree of maturity influenced the benefits of MeJ application. The 100?μmol?l^?1 MeJ treatment had a positive impact on antioxidant systems for GM fruit, whereas a MeJ concentration below 100 μmol l^?1 was found to extend the shelf life of HM fruit.     

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.     

Control of black spot disease caused by Alternaria alternata on jujube (Ziziphus jujuba Mill. cv. Dongzao) using HarpinXoo protein

Summary

Currently, no adequate control measures exist for the fungal disease, black spot (Alternaria alternata (Fr.) Keissler) on ‘Dongzao’ jujube (Ziziphus jujuba Mill. cv. Dongzao). Black spot is an important factor limiting jujube fruit yield under certain conditions. In this study, three concentrations (10, 20, or 30 µg ml^–1) of the Harpin_Xoo protein, or water (negative control), were sprayed onto ‘Dongzao’ jujube trees to control black spot disease. Following Harpin_Xoo protein treatment, its effects on the control of black spot disease were determined, and the levels of a defence-related substance [i.e., salicylic acid (SA)], and the activities of peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) were measured. The incidence of black spot disease was significantly decreased, compared with water-treated control, fruit by ≤ 88.4%. After 2 d, SA levels, and POD, PPO, and PAL activities in Harpin_Xoo-treated fruit were clearly higher than those in control fruit. After fruit had been stored for 45 d at 0ºC, SA levels, and POD and PPO activities showed no differences between the Harpin_Xoo treatments and the controls, but PAL activities in Harpin_Xoo-treated fruit were lower than those in the controls. The most appropriate concentration of Harpin_Xoo protein to control black spot disease was 20 µg a.i. ml^–1. These results suggest that the Harpin_Xoo protein induced systemic acquired resistance in ‘Dongzao’ jujube trees and may offer a worthwhile strategy for disease control.     

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.     

三种暖季型草坪草在干旱条件下脯氨酸含量和抗氧化酶活性的变化

 测定了土壤干旱条件下矮生狗牙根、沟叶结缕草和地毯草相对含水量和相对电导率的变化。结果表明，矮生狗牙根的耐旱性较强，沟叶结缕草次之，而地毯草对干旱敏感。干旱胁迫下，地毯草积累脯氨酸最多，沟叶结缕草次之，矮生狗牙根最少，草坪草的脯氨酸的积累与耐旱性呈负相关。地毯草超氧化物歧化酶(SOD)活性持续升高，过氧化氢酶(CAT)活性在短暂升高后降低，过氧化物酶(POD)活性降低；矮生狗牙根和沟叶结缕草的SOD活性先升后降，CAT和POD活性则维持较高水平，表明草坪草的耐旱性与抗氧化酶活性有关。     

Amount of Cortical and Epidermal Tissue Shed From Roots of Apple

Rates of CO₂ production by cv Idared apples were progressively reduced by lowering O₂ levels from 21% to 2% and 1%. Although lowering the temperature from 4° to 2°C also reduced the respiration rate, fruits stored in 1% and 2% O₂ were respiring faster after 100 days at 0°C than at 2° or 4°C. After 192 days the air-stored fruit also showed an increase in respiration rate at 0°C. These higher respiration rates preceded the development of low temperature breakdown in fruit stored in air, 2% and 1% O₂ at 0°C and in 1% 0₂ at 2°C. Progressively lower O₂ concentrations reduced ethylene production whilst increasing the retention of acid (expressed as malic), soluble solids, chlorophyll and firmness. In the absence of low temperature breakdown the effects of reduced temperature on fruit ripening were similar to those of lowered O₂ concentrations. The quality of apples stored at 4°C in 1% O₂ was markedly better than in 2%; the fruits were also free of core flush (brown core) and other physiological disorders.     

Phenotype analysis of mycelium growth regeneration after heat stress in a Lentinula edodes F2 population

Heat stress is one of the major abiotic stresses that adversely affect growth and yield in Lentinula edodes (Shiitake mushroom) under natural cultivation. In this study, two parental strains (L808 and Lsm9), an F₁ strain, and an F₂ population derived from their hybrid progeny were used to evaluate the regeneration of mycelia after heat stress. A multi-level heat stress experiment showed that the dynamics of radial mycelium expansion of the two parents followed a linear equation after heat stress treatment at 37°C for 4–24 h, 42°C for 4–16 h, or 45°C for 4 h. Three indices were selected to describe the regeneration ability of the strains, including the number of regeneration days (NRD), the real growth rate after heat stress (V_regeneration), and the regenerative index (RI). L808 presented a faster rate of regeneration, while Lsm9 had better regeneration quality. The phenotype analysis of the F₂ population showed that these indices were controlled by multiple genetic factors with high heritability. Four strains were selected from the population, pyramiding the advantages of heat resistance from the two parents. The results will help our understanding of the genetic features of this mushroom after extreme high-temperature stress.