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Volume 6 Number 1 2012 
CONTENTS AND ABSTRACTS
Zong Liu, Roger Sauve, Suping Zhou (USA) Identification of Molecular Mechanism for Freeze Tolerance in Flower Buds of Helleborus orientalis (pp 1-7)
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ABSTRACT
Original Research Paper: Recent changes in climate have led to very dramatic temperature fluctuations in winter and spring. Warmer winters and early springs and sudden temperature dips to subzero in mid to late spring are of common occurrence in the United States of America. Horticultural plants, including spring blooming ornamental species, fruit trees, and vegetables are very vulnerable to such weather conditions. This study was performed to identify genes conferring tolerance to the freeze-thaw stress in flower buds of Helleborus orientalis, using genome wide mRNA profiling (cDNA differential display) and quantitative real-time polymerase chain reaction analysis. Flowers were collected from field plants at frozen-defrosted-recovery stages and an incubator experiment was conducted under a corresponding temperature regime (0-4-10 ± 1°C). Based on expression patterns and putative functions of the isolated genes, programmed cell death, water transportation (aquaporin proteins), and oxidative phosphorylation are proposed to play key roles in the tolerance mechanism for freezing temperature; genes in the biosynthesis of steroids and terpenes were activated as soon as the temperature warmed up to above freezing point. This study provides novel understanding and gene sequences to be used for improving tolerance to subzero freezing temperature in floral plants.
Jing Zhou, Sasikiran Reddy, Suping Zhou, Roger J. Sauvé, Sarabjit Bhatti, Tara Fish, Theodore W. Thannhauser (USA) Effect of Heat Stress on Leaf Proteome and Enzyme Activity in Solanum chilense (pp 8-13)
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ABSTRACT
Original Research Paper: Two-month-old Solanum chilense seedlings were subjected to 40°C heat treatment for 7 days. Comparative proteomics analysis determined that heat affected the abundance level of proteins in the following pathways: photorespiration (glycolate oxidase and hydroxypyruvate reductase), secondary metabolite production (flavonol synthase and NAD-dependent epimerase/dehydratase), photosynthesis-light reaction (ferredoxin reductase and NADPH: protochlorophyllide oxidoreductase), methionine biosynthesis (homocysteine methylase), carbon fixation and metabolism (phosphoglycerate kinase and fructose-bisphosphate aldolase), and ATP regeneration (ATP synthase). The NADPH: protochlorophyllide oxidoreductase and one isoform of glycolate oxidase were induced, and all the other proteins were suppressed by the heat treatment. Enzyme activity assays were performed on two-month-old-seedlings and two-year-old-greenhouse plants subjected to 40-50°C heat treatments. In the two-month old seedlings, heat treatment suppressed hydroxyperuvate reductase activity, but glycolate oxidase activity maintained at similar levels. The two-year-old plants contained higher hydroxyperuvate reductase activity, but lower glycolate oxidase activity compared to the two-month-old seedlings. Peroxidase activity was much higher in the two-year-old plants than the two-month-old seedlings. Plants exposed to the extreme heat at 50°C showed the most dramatic and consistent changes in all of the three enzymes. This study has provided valuable information for the understanding of molecular mechanism for heat tolerance in S. chilense.
Marina I. Azarkovich, Nataliya A. Gumilevskaya (Russia) Response of Dormant Recalcitrant Horse Chestnut (Aesculus hippocastanum L.) Seeds to Heat Shock (pp 14-19)
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Original Research Paper: The effects of heat shock on the in vivo protein synthesis in the embryo tissues of dormant recalcitrant horse chestnut (Aesculus hippocastanum L.) seeds in the course of their stratification were studied. Embryo axes, cotyledon pieces, and cotyledon petioles were excised from seeds in different times after the start of cold stratification and incubated at 28 or 40°С on the medium containing 35S-methionine for 4 h. It was established that, in all embryo parts, especially in axes, heat shock markedly activated protein synthesis in the beginning of stratification and to a lesser degree after ten weeks of stratification; heat shock suppressed protein synthesis at radicle emersion and especially during axial organ growth. None of dominating heat-stable proteins was synthesized either at 28 or 40°С. The synthesis of heat shock proteins did not depend on transcription and occurred on pre-existing mRNAs. First data were obtained concerning functioning molecular mechanisms providing for perception and transduction of heat signal and heat shock proteins synthesis in embryo cells of mature dormant horse chestnut seeds, which were in metabolically active state but could not germinate. The bulk of proteins synthesized by embryo parts at 28°С continued to be synthesized under conditions of heat shock simultaneously with heat shock proteins. It seems evident that, in the embryo cells, heat shock induced changes in gene expression and heat shock proteins synthesis but did not result in translational discrimination of mRNAs for non-heat-shock proteins. It is suggested that such response to heat shock is characteristic just of embryo tissues; it could be considered an additional molecular mechanism improving embryo tolerance to unfavorable environmental conditions.
Mohammad Israil Ansari (India), Jaime A. Teixeira da Silva (Japan) Molecular Analysis of the TLP18.3 Gene in Response to Abiotic Stresses in Arabidopsis thaliana (pp 20-24)
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Original Research Paper: The Arabidopsis thaliana thylakoid lumen 18.3 kDa protein (TLP18.3) gene has a domain of unknown function (DUF477), which is a family of uncharacterized proteins. We have investigated the expression pattern of the TLP18.3 gene in response to different abiotic stresses. The TLP18.3 gene was exclusively up-regulated when plants were exposed to high salt, drought, strong light and methyl viologen while, with treatment with cold and osmotic stress, it was down-regulated. Furthermore, a A. thaliana TLP18.3 T-DNA insertion mutant (SALK_109618) and wild type plants were examined for water loss. In post-germination, root length was measured during stress condition both in wild and mutant plants. As a result, in the TLP18.3 T-DNA insertion mutant plants, root length was much more affected than wild type, so water loss was greater than in wild type plants. Taken together, these results suggest that the TLP18.3 gene is involved in the response of A. thaliana plants to abiotic stresses.
Moaed Almeselmani (Syria), P.S. Deshmukh, Viswanathan Chinnusamy (India) Effects of Prolonged High Temperature Stress on Respiration, Photosynthesis and Gene Expression in Wheat (Triticum aestivum L) Varieties Differing in their Thermotolerance (pp 25-32)
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Original Research Paper: High temperature (HT) stress is a major environmental stress limiting wheat productivity worldwide. This study was conducted to analyze the effect of prolonged HT on wheat genotypes C306 (HT tolerant) and PBW343 (HT susceptible) in controlled environment chambers. After an initial 45-days growth at 23/18°C day/night, one set of plants (control) was maintained at the same conditions, while the other set of plants was exposed to HT (35/25°C day/night). Effect of heat stress was analyzed after one week (vegetative), 30-days (anthesis) and 45-days (15 days after anthesis) of HT. HT significantly reduced the leaf chlorophyll (chl) content, photosynthetic rate and Rubisco activity in both the genotypes at all the growth stages. However, the reduction was more in heat-susceptible genotype PBW343 than heat-tolerant genotype C306. C306 showed higher respiratory homeostasis than PBW343, under prolonged heat stress. Heat tolerant C306 showed less reduction in photosynthesis and maintained respiration, while heat susceptible PBW343 showed higher reduction in photosynthesis accompanied by significant increase in respiration. Better tolerance in photosynthesis to long-term heat stress in C306 can be attributed to less reduction in total chl and chl b content and Rubisco activity. Maintenance of Rubisco activity in C306 under HT may be due to maintenance of expression of rbcS and rbcL genes. Maintenance of high expression levels of HSP101 during long-term heat stress in C306 may also be reason for better tolerance of C306 as compared with PBW343, as HSP101 is crucial for both basal and acquired thermotolerance.
Safaa Najla (France/Syria), Gilles Vercambre, Michel Génard (France) Effects of Water Deficit and Variations of Fruit Microclimate on Peach Fruit Growth and Quality (pp 33-38)
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Original Research Paper: This study was carried out to determine the response of peach tree (Prunus persica L. Batsch cv ‘Alexandra’) to water stress and variations of fruit microclimate during the final stage of rapid fruit growth. Two irrigation treatments (standard and deficit irrigations) were applied. Fruit microclimatic conditions were modified by enclosing the fruits in plastic films covered with two types of foil (osmolux and P+). Fruit and stem potentials showed significant differences between treatments. In the deficit irrigation treatment, tree water potential decreased (-22 bars compared to -15 bars in the case of the treatment with standard irrigation) while at the same time, a fluctuation of the stem diameter was observed. The combined effects of water stress and modified microclimatic conditions affected the fruit water status and, consequently, fruit growth parameters. Water stress slowed the xylem flow into the fruit (-36%) and induced a significant reduction in the fruit diameter, fruit fresh and dry masses and soluble solids content. On the other hand, bagging of the fruits with the two types of plastics did not modify fruit diameter, fruit fresh mass and soluble solids content. However, the osmolux plastic induced a significant reduction in the fruit dry mass. Water stress induced a significant decrease of fruit conductance whereas covering fruits with P+ plastic induced its increase. This increase is followed by a reduction of the transpiration rate (due to the moisture raised in the film of P+).
Sasan Mohsenzadeh, Maryam Shahrtash (Iran), Jaime A. Teixeira da Silva (Japan) Silicon Improves Growth and Alleviates Toxicity of Cadmium in Maize Seedlings (pp 39-43)
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Original Research Paper: The protective effect of silicon against cadmium (Cd) toxicity in maize seedlings was investigated. Cd is a strong environmental pollutant that negatively affects plant growth. The seedlings were treated with Cd at 100 μM for 9 days. The application of 50, 100 and 150 mM silicon was able to alleviate Cd toxicity and improve growth parameters through some mechanisms. For example, shoot and root fresh weight increased significantly from 2.47 and 1.05 g per pot to 3.11 and 1.61 g per pot, respectively. The alleviation showed by silicon adding to Cd treatment seedlings through declining in lipid peroxidation, proline and Cd uptake and rising in chlorophyll, carotenoid, shoot and root fresh and dry weight and relative water content compared to Cd-stressed seedlings, significantly.
Morteza Saberi, Alireza Shahriari (Iran), Jaime A. Teixeira da Silva (Japan), Farajollah Tarnian, Ali Tavili (Iran) Influence of Salicylic Acid on Bromus tomentellus Germination and Initial Growth Properties under Cadmium Stress (pp 44-48)
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Original Research Paper: Biotic and abiotic stresses affect germination and the growth of plants. Heavy metals such as cadmium (Cd) can decrease seed germination and the growth of plants. Salicylic acid (SA) is able to reduce the negative effect of heavy metals. The current study was carried out to investigate the effect of SA on germination and on initial growth properties of Bromus tomentellus under Cd stress. Therefore, B. tomentellus seeds were pretreated with 0, 100, 200 and 300 mg/L of SA for 10 h and then placed under stress with Cd at 0, 10, 20 and 30 mg/L. Results indicated that Cd reduced germination percentage from 57% in the control to 40% at 30 mg/L Cd solution without SA pretreatment. Speed of germination was increased to 200 mg/L SA and then decreased. Cd also caused a decrease on it by increasing Cd levels. Results also indicated that Cd reduced plumule length from 5.2 cm in the control to 1.7 cm at 30 mg/L Cd solution without SA pretreatment and radicle length was reduced from 2.4 cm in the control to 0.3 cm at 30 mg/L Cd solution without SA pretreatment. The highest values of plumule and radicle lengths were at 200 and 300 mg/L of SA under Cd stress, respectively.
Soha E. Khalil, Mohamed M. Hussein (Egypt), Jaime A. Teixeira da Silva (Japan) Roles of Antitranspirants in Improving Growth and Water Relations of Jatropha curcas L. Grown under Water Stress Conditions (pp 49-54)
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Original Research Paper: In recent years, deficit irrigation has been widely investigated as a valuable and sustainable production strategy in Egypt. Also, in response to rising oil prices and the quest for alternative economically viable and environmentally sustainable forms of energy, certain plant species with bio-energy potential have been proposed for large-scale planting and bio-fuel production. Hence, the present investigation was conducted in a greenhouse during the two consecutive summer seasons to investigate the effects of three soil moisture levels (85, 55, and 25% depletion of the available soil water), and four antitranspirant treatments (control, 6% kaolin, 6% MgCO3, and 6% kaolin + MgCO3) which were sprayed twice during the plant’s life (the first after 60 days from planting and the second 4 weeks later) and their interactions on growth attributes, percentage relative water content (RWC%), osmotic pressure, Pro content and percentage carbohydrates of Jatropha curcas L. Results indicated that increasing water stress significantly retarded growth attributes and RWC%. On the contrary, increasing severity of drought caused a significant increase in osmotic pressure, Pro content and percentage carbohydrates. A spray with antitranspirants markedly increase all growth attributes and RWC% while osmotic pressure, Pro content and percentage carbohydrates decreased markedly compared with control plants. The interaction effect between soil moisture levels and antitranspirant treatments was significant for all the studied parameters in both seasons. Highest values were observed in plants watered with the highest soil moisture level (25% depletion of the available soil water) and which received 3% kaolin + 3% MgCO3 which had a greater effect.
Sandeep Kumar, Geetika Sirhindi, Renu Bhardwaj, Manish Kumar, Priya Arora (India) Role of 24-Epibrassinolide in Amelioration of High Temperature Stress through Antioxidant Defense System in Brassica juncea L. (pp 55-58)
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Original Research Paper: The present work was undertaken to study the role of different concentrations of 24-epibrassinolide (24-EBL) (10-10, 10-8 and 10‑6 M) on growth, the activity of antioxidant enzymes like catalase (CAT), ascorbate peroxidase (APOX) and superoxide dismutase (SOD) and total protein content in 10-days-old seedlings of Brassica juncea L.exposed to heat stress for 5 hrs daily for three consecutive days. Heat treatment lowered total protein content of B. juncea seedlings. Seedlings treated with different concentrations of 24-EBL had better growth and enhanced protein content than the control. Similarly, the activity of SOD, CAT, APOX, PPO, and auxinases were enhanced following the application of different concentrations of 24-epiBL. APOX activity was most enhanced by 10-10 M 24-epiBL, while 10-8 M most enhanced the activity of CAT and SOD. Temperature stress ameliorated the effect of 24-epiBL on seedlings.
Nisar Ahmad Shah, Jai Prakash Srivastava (India), Jaime A. Teixeira da Silva (Japan), Jai Prakash Shahi (India) Morphological and Yield Responses of Maize (Zea mays L.) Genotypes Subjected to Root Zone Excess Soil Moisture Stress (pp 59-72)
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Original Research Paper: Waterlogging is one of the major constraints limiting maize (Zea mays L.) production, especially on the Indian subcontinent. The present study was carried out to evaluate 10 maize genotypes for morphological and yield responses under root zone excess soil moisture stress. Excess soil moisture stress was imposed by flooding the field for five days at the knee height and taselling stages. As a consequence of stress, a significant reduction in total leaf number including green leaves and dead leaves, leaf area, dry matter accumulation, yield and yield attributes, was observed. Nodal root number increased under stress condition. Days to 50% anthesis and ear emergence was delayed. The duration between anthesis to silking was widened under excess soil moisture stress. Reduction in grain yield increased when plants were exposed to stress at the knee height stage. When waterlogging was impose at the knee height stage, there was a 43% reduction in grain yield, but yield was reduced by 25% when stress was imposed at the taselling stage. The genotypes ‘V-32’, ‘V-33’, and ‘CML-204’ were relatively resistant to excess soil moisture stress while ‘CML-56’, ‘CM-119’, and ‘CM-211’ were susceptible. An increase in nodal root number, and reduced widening in the anthesis-silking interval caused by waterlogging are suggested as being parameters for rapid screening of excess soil moisture stress-resistant maize genotypes.
Javad Lamei, Khoshnoud Alizadeh (Iran), Jaime A. Teixeira da Silva (Japan), Mohammad Vali Taghaddosi (Iran) Vicia panonica: A Suitable Cover Crop for Winter Fallow in Cold Regions of Iran (pp 73-76)
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Original Research Paper: In order to compare the yield potential of three cover crops, namely wheat (Triticum aestivum cv. ‘Alvand’), barley (Hordeum vulgare cv. ‘Makoeie’) and Hungarian vetch (Vicia panonica cv. ‘Vp-2670’), an investigation was carried out over two years (2006-2008) at the Kheyrabad Agricultural Research Station, Zanjan, Iran. Cover crops were planted under irrigated conditions in late September. The amount of dry matter (DM), crude protein (CP), and percentage of nitrogen (N), phosphorus (P) and potassium (K) in DM were determined when vetch reached the 50% flowering stage, coinciding with the milky stages of wheat and barley. A combined analysis showed that the main effect of year and cover crop on DM, CP and the percentage of N and P was significant (P < 0.01); wheat and vetch produced the highest and least amount of DM, 9.72 and 5.49 t/ha, respectively. Crops reacted similarly to environmental conditions. Mean performance of CP in vetch (897 kg/ha) differed significantly from the cereal cover crops which could be attributed to the highest N content (2.6%) detected in its DM. Due to its higher potential N and CP performance, Hungarian vetch is a recommended winter fallow crop for cold areas.
Elnaz Hatami, Mahmood Esna-Ashari, Taimoor Javadi (Iran) Effect of Salinity on Some Growth Characteristics and Concentration of Elements in Two Grape (Vitis vinifera L.) Cultivars, ‘Rishbaba’ and ‘Sahebi’ (pp 77-80)
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Original Research Paper: Two grape (Vitis vinifera L.) cultivars (‘Rishbaba’ and ‘Sahebi’) were subjected to different concentrations of NaCl and some growth characteristics, including shoot length, specific leaf area, leaf number and root dry weight to stem dry weight ratio were determined, as was the concentration of some elements including Na+, Cl-, K+ and Ca2+ in roots and leaves. The project was conducted in a factorial experiment based on a complete randomized block design with four replications. Salinity levels were 0 (control), 25, 50, 75, 100, 125 and 150 mM NaCl. Rooted cuttings were cultivated in pots containing perlite and fed with Hoagland’s nutrient solution. Plants treated with salinity were kept for 20 days. Results showed that by increasing salinity level, shoot length, specific leaf area and leaf number decreased significantly. Because growth reduction in the shoots was higher than the roots, by increasing salinity level the ratio of root dry weight to stem dry weight increased. Salt stress had a significant effect on Na+, Cl-, K+ and Ca2+ concentrations in both roots and leaves. Increasing salinity level caused an increase in Na+ and Cl- concentrations in roots and leaves. This increase was observed more in roots than the leaves and was higher in ‘Rishbaba’ showing low transportation of the above ions to the upper sections of the plants in this cultivar. Increasing salinity levels decreased K+ and Ca2+ concentrations in tissues. This reduction was more in the roots than in the leaves. ‘Rishbaba’ transported more Ca2+ to upper plant sections. Based on the results of this experiment, ‘Rishbaba’ was more tolerant to salinity stress than ‘Sahebi’. |
