Increased Root Fresh Weight Research Articles

Melatonin Ameliorates Cadmium Toxicity in Tobacco Seedlings by Depriving Its Bioaccumulation, Enhancing Photosynthetic Activity and Antioxidant Gene Expression

Soil remediation for cadmium (Cd) toxicity is essential for successful tobacco cultivation and production. Melatonin application can relieve heavy metal stress and promote plant growth; however, it remains somewhat unclear whether melatonin supplementation can remediate the effects of Cd toxicity on the growth and development of tobacco seedlings. Herein, we evaluated the effect of soil-applied melatonin on Cd accumulation in tobacco seedlings, as well as the responses in growth, physiological and biochemical parameters, and the expression of stress-responsive genes. Our results demonstrate that melatonin application mitigated Cd stress in tobacco, and thus promoted plant growth. It increased root fresh weight, dry weight, shoot fresh weight and dry weight by 58.40%, 163.80%, 34.70% and 84.09%, respectively, compared to the control. Physiological analyses also showed significant differences in photosynthetic rate and pigment formation among the treatments, with the highest improvements recorded for melatonin application. In addition, melatonin application alleviated Cd-induced oxidative damage by reducing MDA content and enhancing the activities of enzymatic antioxidants (CAT, SOD, POD and APX) as well as non-enzymatic antioxidants (GSH and AsA). Moreover, confocal microscopic imaging confirmed the effectiveness of melatonin application in sustaining cell integrity under Cd stress. Scanning Electron Microscopy (SEM) observations illustrated the alleviative role of melatonin on stomata and ultrastructural features under Cd toxicity. The qRT-PCR analysis revealed that melatonin application upregulated the expression of photosynthetic and antioxidant-related genes, including SNtChl, q-NtCSD1, NtPsy2 and QntFSD1, in tobacco leaves. Together, our results suggest that soil-applied melatonin can promote tobacco tolerance to Cd stress by modulating morpho-physiological and biochemical changes, as well as the expression of relevant genes.

Vermicompost application upregulates morpho-physiological and antioxidant defense to conferring drought tolerance in wheat

Drought stress is an ever‐present threat to wheat growth, development, and productivity, especially in arid and semi-arid areas where rainfall is an essential aid to agriculture. The application of vermicompost has been proven to be an efficient approach to combat the drought-induced growth and developmental limitation of wheat plants and to promote cost-effective and sustainable crop production. A wire-house pot experiment was conducted to examine the effects of cow manure vermicompost on morpho-physiological and biochemical attributes of wheat seedlings under different deficit water levels. The treatments were included: three drought levels; control (70 % of field capacity (FC, D0)), mild drought (45 % of FC, D1), and severe drought (30 % of FC, D1), four vermicompost application rates; control, 4, 6 and 8 t ha−1 (designated as VT0, VT1, VT2 and VT3, respectively), and two contrasting wheat cultivars; Faisalabad-08 (drought tolerant) and Galaxy-13 (drought sensitive). Results showed that vermicompost application improved crop performance under control and drought stress conditions where VT2 depicted significantly higher values in both cultivars, particularly under drought stress. Under severe drought, VT2 increased root fresh weight by 6.13 and 10.63 %, shoot fresh weight by 15.62 % and 23.58 %, root dry weight by 40.81 % and 50 % and shoot dry weight by 20.68 and 22.22 % in Faisalabad-08 and Galaxy-13, respectively. Also, VT2-treated seedlings exhibited significantly higher gas exchange attributes, chlorophyll pigments and antioxidative enzyme activities under drought conditions. Among cultivars, Faisalabad-08 was found comparatively more drought tolerant than Galaxy-13. Our findings demonstrated that drought severely affects morphological, physiological, and biochemical attributes of wheat. However, soil applied vermicompost proved beneficial for improved morphophysiological and biochemical traits under the regime of drought stress in wheat.

Physiological mechanisms of exogenous organic acids to alleviate aluminum toxicity in seedlings of mungbean, buckwheat, and rice

One of the major constraints for crop yield in acidic soils is the phytotoxicity of aluminum ions (Al3+), which primarily affects the roots. To mitigate the harmful effects of Al toxicity, plants use organic acids to chelate Al internally and externally. In this study, the effects of exogenous organic acids on Al toxicity in rice, mung bean, and buckwheat were investigated. Specifically, the study examined the ameliorative effect of three organic acids (oxalic acid, malic acid, and citric acid, each at a concentration of (100 μmol/L) on root elongation, fresh weight, Al content, organic acid key enzymes, and rhizosphere pH in hydroponic media containing (100 μmol/L) Al. The experimental results revealed species-specific responses to aluminum tolerance and the alleviating effects of different organic acids. Buckwheat was found to be the most aluminum-tolerant, followed by mung bean, while rice was the least tolerant. Exogenous application of oxalic acid promoted root elongation, increased root fresh weight, and enhanced the activity of the PEPC enzyme in mung bean. Malic acid, on the other hand, alleviated Al toxicity in rice by promoting root elongation, increasing root fresh weight, enhancing the activity of the PEPC enzyme, and decreasing the activity of the MDH enzyme. In buckwheat, citric acid application reduced Al toxicity by promoting root elongation, increasing root weight, and decreasing the activities of CS and GO enzymes. These findings indicate that different organic acids can reduce Al toxicity in different plant species by employing different physiological mechanisms.

The response of oil palm seedlings' growth to vermicompost and water stress under the main nursery stage

The availability of nutrients and water are two things that are essential for the development of plants. Future oil palm agriculture will require a strategy for the management of water because of the erratic nature of the weather. The addition of organic matter, such as vermicompost, is one strategy for addressing the issue of insufficient water supplies. The primary objective of this study is to investigate the relationship between oil palm seedlings' exposure to vermicompost and various levels of water stress in the main nursery. During the three-month study, 100, 200, and 300 g of vermicompost per polybag was combined with 1.0, 1.5, and 2.0 L/polybag/day. There was no relationship between the dose of vermicompost and the water stress that had observed. The addition of 300 g/polybag of vermicompost increased root fresh weight by 37.8% compared to 100 g/polybag. Moreover, water stress leads to a reduction in plant height and dry weight of the shoots. Compared to 2 L/polybag/day, plant height was lowered by 23.3% and 19.8% at watering volumes of 1.0 and 1.5 L/polybag/day, respectively. In addition, when compared to the appropriate water level of 2 L/polybag/day, high water stress (1.0 L/polybag/day) declined shoot dry weight by 12%.

Bacterial Inoculant and Sucrose Amendments Improve the Growth of Rheum palmatum L. by Reprograming Its Metabolite Composition and Altering Its Soil Microbial Community.

Rheum palmatum L. is an important traditional Chinese medicinal herb now in demand worldwide. Recently, the theoretical framework suggested that sucrose triggers colonization of PGPM (plant growth-promoting microbes) in the rhizosphere, but their interactions on the plant remain largely unknown. Here, we applied three concentrations of both Bacillus amyloliquefaciens EZ99 inoculant (1.0 × 105, 1.0 × 106, and 1.0 × 107 colony-forming units (CFU)/mL, denoted as LB, MB, and HB, respectively) and sucrose (0.15, 1.5, and 15 g/L, denoted as LS, MS, and HS, respectively) to investigate their co-effects on R. palmatum in a field experiment. The results showed that LB + MS (1.0 × 105 CFU/mL Bacillus + 1.5 g/L sucrose) and LB + LS (1.0 × 105 CFU/mL Bacillus + 0.15 g/L sucrose) treatments significantly increased root fresh weight (p ≤ 0.05). Metabolite analysis revealed that the treatment LB + LS significantly increased the relative content of major active components in rhubarb, namely anthraquinones and phenolic compounds, by 1.5% and 2.3%. Although high sucrose addition increased the activities of certain soil enzymes, the LB + LS treatment significantly increased total potassium (TK), whereas it decreased available potassium (AK), which facilitated the potassium utilization in rhizosphere soil. Furthermore, rhizosphere microbiomes revealed that fungal diversity was augmented in LB + LS treatment, in which the common causative fungal pathogen Fusarium spp. showed an effective suppression. Additionally, the redundancy analysis and Spearman correlations revealed a positive relationship of Sphingomonas associated with change in potassium bioavailability. Altogether, our findings suggest that the combined application of a bacterial inoculant and sucrose can improve the growth and quality of R. palmatum, and stimulate uptake of plant nutrients that contribute to alter the microbial community for biocontrol potential. Hence, this work not only has broad application prospects across economical plants, but also emphasizes agroecological practices for sustainable agriculture.

Effects of growth promoting microorganisms on tomato seedlings growing in different media conditions.

Plant growth-promoting microbes (PGPM) play vital roles in maintaining crop fitness and soil health in stressed environments. Research have included analysis-based cultivation of soil-microbial-plant relationships to clarify microbiota potential. The goal of the research was to (i) evaluate the symbiotic microorganism effects on tomato seedling fitness under stressed conditions simulating a fragile soil susceptible to degradation; (ii) compare the plant-microbial interactions after inoculation with microbial isolates and fungi-bacteria consortia; (iii) develop an effective crop-microbial network, which improves soil and plant status. The experimental design included non-inoculated treatments with peat and sand at ratios of 50:50, 70:30, 100:0 (v:v), inoculated treatments with arbuscular mycorrhizal fungi (AMF) and Azospirillum brasilense (AZ) using the aforementioned peat:sand ratios; and treatment with peat co-inoculated with AMF and Saccharothrix tamanrassetensis (S). AMF + AZ increased root fresh weight in peat substrate compared to the control (4.4 to 3.3 g plant-1). An increase in shoot fresh weight was detected in the AMF + AZ treatment with a 50:50 peat:sand ratio (10.1 to 8.5 g plant-1). AMF + AZ reduced antioxidant activity (DPPH) (18-34%) in leaves, whereas AMF + S had the highest DPPH in leaves and roots (45%). Total leaf phenolic content was higher in control with a decreased proportion of peat. Peroxidase activity was enhanced in AMF + AZ and AMF + S treatments, except for AMF + AZ in peat. Microscopic root assays revealed the ability of AMF to establish strong fungal-tomato symbiosis; the colonization rate was 78-89%. AMF + AZ accelerated K and Mg accumulation in tomato leaves in treatments reflecting soil stress. To date, there has been no relevant information regarding the successful AMF and Saccharothrix co-inoculation relationship. This study confirmed that AMF + S could increase the P, S, and Fe status of seedlings under high organic C content conditions. The improved tomato growth and nutrient acquisition demonstrated the potential of PGPM colonization under degraded soil conditions.

Investigation of Distinctive Morpho-Physio and Biochemical Alterations in Desi Chickpea at Seedling Stage Under Irrigation, Heat, and Combined Stress.

Global climatic instabilities have become the main reason for drastic yield losses in chickpea. This shift in climate could be a great threat in the future for food security in developing countries. Chickpea production is badly hampered by heat stress coupled with drought stress, and these factors can reduce yields by 40–45%. To mitigate yield losses due these abiotic factors, irrigation supplementation could be the best strategy. The present study aimed to (i) investigate the tolerance response of 9 desi chickpea genotypes against heat stress (H), irrigation (I), and a combination of both (I+H) through morphophysiological and biochemical indices at early growth stage, and (ii) assess yield performance across multiple locations of the country. Results revealed that under irrigation treatment, all genotypes perform well, but the genotypes D-09027 and D-09013 showed best performance because, as compared to control, they retained root length, seedling fresh weight, root fresh weight, root dry weight, esterase activity, Malondialdehyde (MDA) content, total chlorophyll, and total carotenoids. Shoot length and total phenolic contents (TPC) increased in both genotypes. Superoxide dismutase (SOD) and peroxidase (POD) increased in D-09027 and retained in D-09013. Catalase activity increased in D-09013 and retained in D-09027. Protease activity, total water potential and osmotic potential decreased in both genotypes and depicted high yield potential with 27 and 30% increase in yield over Bhakhar-2011 (check), respectively. In case of heat stress, maximum tolerance was found in genotypes CH104/06 and D-09013 with no change in shoot and root length, seedling dry weight, shoot fresh and dry weight, root dry weight, relative water content, turgor water potential, catalase (CAT) activity, esterase activity, increased root fresh weight, peroxidase activity (POD), ascorbate peroxidase activity (APX), and lycopene with low accumulation of protease and Malondialdehyde content (MDA). Both genotypes depicted high yield potential with 30 and 43% increase in yield over check across multiple locations of the country. Under the combined treatment, most genotypes showed good performance, while CH104/06 was selected as best performer genotype because significant of its increased root fresh weight, lycopene content, chlorophyll b, total carotenoids, total chlorophyll, retained shoot length, root length, seedling fresh and dry weight, total water potential, osmotic potential, relative water content, peroxidase activity (POD), catalase, esterase, and its ascorbate peroxidase (APX) activity and total soluble proteins (TSP) showed highest yield potential with 43% increase over check. Identified best performing and tolerant genotypes can further be employed for breeding climate-smart chickpea genotypes for sustainable production under changing climate.

Effect of different concentrations of indole butyric acid, putrescine and hydrogen peroxide on stem cuttings of the rootstock GF677(Prunus amygdalus × Prunus persica) according to the cutting season

The rootstock GF677 is an interspecific hybrid with an important economic and horticultural value. In this research, the effect of indole butyric acid (IBA) in combination with putrescine (Put) and hydrogen peroxide (H2O2) on rooting of GF677 semi-hardwood stem cuttings in three cutting seasons (July, March and October) was investigated. Treatments as IBA (0, 1000, 2000 and 3000 mg L-1), Put (0, 800, 1600 and 3200 mg L-1) and H2O2 (1.5, 3 and 6% w/v) were included. The results showed that in July cuttings, the highest levels of callogenesis were observed in IBA treated cuttings in both concentrations of 1000 and 2000 mg L-1. The rooting was very low in July cuttings, while the highest percentage of rooting (14%) was observed in the combination of 2000 mg L-1 IBA+ 3% H2O2. In March, the cuttings treated by 1000 mg L-1 IBA+800 mg L-1 Put and 1000 mg L-1 IBA+1600 mg L-1 Put revealed the highest percentages of callus formation 83.31 and 83.33%, respectively. In these cuttings, the highest percentage of rooting (63.88%) was gained at 2000 mg L-1 IBA+3200 mg L-1 Put. The application of 1000 mg L-1 IBA+800 mg L-1 Put increased root fresh weight. In cuttings prepared in October, only 800 mg L-1 Put caused callus formation in more than 55% of the cuttings. The rooting of cuttings at this time was as low as the July cuttings, whereas the highest rooting percentage was observed in cuttings treated with IBA at a concentration of 1000 mg L-1. Overall, the experiment showed that the season of the cutting and the treatments with IBA+Put or H2O2 could improve rooting properties of the rootstock GF677.

Morphological characters of root and yield of three cocoa (Theobroma cacao L.) clones in the field with dead-end trench

Cocoa (Theobroma cacao L.) is a perennial crop originated from tropical regions, divided into Criollo, Forastero, and Trinitario. Demand for cocoa has increased, but the productivity is still low. The increase in production could be achieved by improving crop management and using superior clones. RCC-70, RCC-71, and KKM-22 are recommended as the superior cocoa clones. Dead-end trench can reduce erosion and surface run-off as well as improve rooting and soil organic matter sequestration. The objectives of this research were to study the effects of dead-end trench application on morphological characters of roots and yields of three cocoa clones and to determine which cocoa clone(s) performed a signifificant yield increase with the application of dead-end trench. The research was conducted in August 2018–April 2019 at Pagilaran Ltd. cocoa plantation in North Segayung Production Unit, subdistrict Tulis, Batang, Central Java. The experiment was arranged in a randomized complete block design with two factors and three replications as block. The first factor was dead-end trench application (with and without dead-end trench application) and the second factor was cocoa clones (RCC-70, RCC-71, and KKM-22). This study showed that application of dead-end trench and clones significantly increased root fresh weight, root dry weight, seed fresh weight, and seed dry weight, but had no significant effect on fruit diameter, fruit length, root length, and root surface area. RCC-70 clone, coupled with the application of dead-end trench, resulted in the highest seed dry weight compared to RCC-71 and KKM-22 clones.

Root bacterial endophytes as potential biological control agents against fungal rice pathogens

The present work was carried out to investigate the potential of 100 rice endophytic bacteria for the biocontrol of five fungal rice pathogens in a controlled environment. As well as, isolates with antagonistic activity were also characterized in terms of production of some plant growth promoting (PGP) traits. Twenty-three isolates repressed the mycelial growth of some fungal rice pathogens (70–96% inhibition). The results illustrated that production ability of PGP traits was different among biocontrol isolates. Higher % of the isolates was positive for generation of ACC deaminase, IAA, and activity of cellulase and pectinase. The effective isolate was identified as Bacillus cereus. This strain also colonized root of rice seedlings and increased root fresh weight (31.4%) and shoot dry weight (28.2%) in vitro. These results showed that endorhiza of rice harbors effective antagonistic bacteria with multiple PGP traits which can be used as a potent biocontrol or biopromoting agent in rice plant.

Effects of different levels of glycine in the nutrient solution on the growth, nutrient composition, and antioxidant activity of coriander (Coriandrum sativum L.)

A nutrient solution experiment was performed using sand culture to evaluate the effects of different glycine levels on the growth and nutrient uptake of coriander (<em>Coriandrum sativum</em> L.). Different glycine concentrations of 0, 5, 10, 20, or 40 mg L<sup>−1</sup> were applied to plants via Hoagland’s nutrient solution in a completely randomized design with four replications and under greenhouse conditions. The results showed that leaf SPAD (soil and plant analysis development; an indicator of leaf greenness) value, stem diameter, and fresh and dry weights of shoots and roots were significantly increased by 10 mg L<sup>−1</sup> glycine in comparison to the control plants. Application of glycine at 40 mg L<sup>−1</sup> reduced many plant growth parameters, whereas leaf proline concentration was increased. All glycine levels except for 40 mg L<sup>−1</sup> increased root fresh weight. Leaf protein content was increased by glycine applied at 10 or 20 mg L<sup>−1</sup>, whereas leaf antioxidant activity was increased at all glycine levels. Application of glycine increased leaf concentrations of nitrogen and potassium (at 10 mg L<sup>−1</sup>), magnesium (at 5 mg L<sup>−1</sup>), and zinc (at all glycine levels) compared to the control plants. The results indicate that moderate level of glycine (10 mg L<sup>−1</sup>) in the nutrient solution can improve the growth and nutritional quality of coriander.

Cysteine-induced alterations in physicochemical parameters of oat (Avena sativa L. var. Scott and F-411) under drought stress.

Drought is one of the major abiotic stresses that drastically reduces crop yield throughout the world. Being precursor of glutathione biosynthesis and involvement in other metabolic processes, cysteine (Cys) has been shown to alter growth and development in plants. In this context, we investigated Cys-induced physicochemical alterations in oat (Avena sativa L. var. Scott and var. F-411) plants under drought stress. There were two levels of drought stress, i.e., control (100% field capacity) and drought (50% field capacity) and three levels of foliar application of Cys, i.e., 0, 10, and 20 mM. Experimental design was completely randomized block design. Drought stress significantly decreased growth parameters, chlorophyll (Chi) contents, while increased leaf membrane permeability (MP), ascorbic acid (AsA), and activity of catalase (CAT) and peroxidase (POD) enzymes. Foliar application of varying Cys levels significantly increased root fresh weight, root length, photo synthetic pigments (chl. a and b), AsA contents in var. Scott, and shoot length, total free amino acids, total phenolics and free proline contents in var. F-411. Of the two oat varieties, var. Scott proved better in root fresh weight, root length, chl. a and b contents, and total phenolic contents, while var. F-411 was higher in the values of shoot length, MP (%), total free amino acids, and free proline contents. Thus, on the basis of strong root system, total phenolics, and more photosynthetic contents (chl. a and b contents), var. Scott could be grown under semi-arid environments than that of var. F-411.

A CRISPR/Cas9 deletion into the phosphate transporter SlPHO1;1 reveals its role in phosphate nutrition of tomato seedlings.

In vascular (Arabidopsis thaliana) and non-vascular (Physcomitrella patens) plants, PHOSPHATE 1 (PHO1) homologs play important roles in the acquisition and transfer of phosphate. The tomato genome contains six genes (SlPHO1;1-SlPHO1;6) homologous to AtPHO1. The six proteins have typical characteristics of the plant PHO1 family, such as the three Syg1/Pho81/XPRI (SPX) subdomains in the N-terminal portion and one ERD1/XPR1/SYG1 (EXS) domain in the C-terminal portion. Phylogenetic analysis revealed that the SlPHO1 family is subdivided into three clusters. A pairwise comparison indicated that SlPHO1;1 showed the highest level of sequence identity/similarity (67.39/76.21%) to AtPHO1. SlPHO1;1 deletion mutants induced by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 displayed typical phenotypes of Pi starvation, such as decreased shoot fresh weight and increased root fresh weight, therefore having a greater root-to-shoot ratio. Mutants also accumulated more anthocyanin and had more soluble Pi content in the root and less in the shoot. These results indicate that SlPHO1;1 plays an important role in Pi transport in the tomato at seedling stage.

Effect of Trichoderma spp. and Purpureocillium lilacinum on Meloidogyne javanica in commercial pineapple production in Kenya

Plant-parasitic nematodes, in particular Meloidogyne species, cause significant yield reduction in commercial pineapple, Ananas comosus, worldwide. The efficacy of three Trichoderma isolates (Trichoderma asperellum M2RT4, T. atroviride F5S21, Trichoderma sp. MK4) and two isolates of Purpureocillium lilacinum (KLF2 and MR2) were evaluated against Meloidogyne javanica, using rooted pineapple crowns in a pot experiment under greenhouse conditions. All the three Trichoderma isolates successfully colonized pineapple root endophytically. The application of two isolates of Trichoderma (T. asperellum M2RT4 and Trichoderma sp. MK4) and the two isolates of P. lilacinum significantly reduced nematode egg and egg mass production reducing root galling damage by between 60.8 and 81.8% and increased the plant root mass growth compared to the untreated control. T. asperellum M2RT4 most effectively reduced galls, egg mass and eggs, by 81.8, 78.5 and 88.4% respectively. P. lilacinum MR2 most effectively reduced galls, egg mass and eggs, by 71.6, 73.9 and 82.6% respectively. In contrast Trichoderma atroviride F5S21 application had no significant effect on nematode multiplication or root damage compared with the control. Inoculation with T. asperellum M2RT4 increased root fresh weight by 91.5%, Trichoderma sp. MK4 by 63.8%, T. atroviride F5S21 by 50.0%, P. lilacinum KLF2 by 43.8% and MR2 by 32.3%. Results indicate that local isolates Trichoderma spp. and P. lilacinum directly and indirectly affected nematode reproduction and host response, demonstrating their control potential against M. javanica on pineapple. Such alternative options for managing Meloidogyne spp. would provide more environmentally sensitive options for combining with other management methods towards more sustainable pineapple production systems.

干旱条件下接种AM真菌对小马鞍羊蹄甲幼苗根系的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱条件下接种AM真菌对小马鞍羊蹄甲幼苗根系的影响 DOI: 10.5846/stxb201601280209 作者: 作者单位: 中国科学院生态环境研究中心,中国科学院生态环境研究中心,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31170581） Inoculation with arbuscular mycorrhizal fungi enhances the root system of Bauhinia faberi var. microphylla seedlings under drought stress conditions Author: Affiliation: Research center for Eco-Environmental Sciences,Chinese Academy of Sciences,Research center for Eco-Environmental Sciences,Chinese Academy of Sciences,Research center for Eco-Environmental Sciences,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探讨岷江干旱河谷丛枝菌根真菌（AMF）对寄主植物幼苗根系的影响，通过接种购买的AMF摩西球囊霉菌（Funneliformis mosseae）到优势乡土灌木小马鞍羊蹄甲（Bauhinia faberi var. microphylla）幼苗，在重度、中度和轻度干旱条件下培养3个月，研究不同干旱条件下AMF对幼苗根系形态特征、结构特征、功能性状的影响。方差分析结果表明：（1）3种干旱胁迫条件下，接菌均显著增加了幼苗的根总长、根表面积、根分枝数、根尖数（P < 0.001），在中度胁迫和轻度胁迫下，接菌显著促进根鲜重、根体积的增加（P < 0.001），轻度胁迫条件下接菌幼苗的根鲜重、根总长、根表面积、根体积、根尖数最高并显著高于其它处理，但接菌与未接菌的根平均直径之间没有显著差异；（2）接菌幼苗根系趋向于叉状分支结构，在重度胁迫时，叉状分支趋势更显著（P < 0.001）；（3）接菌幼苗的根比例都显著小于未接菌的，但幼苗比根长不存在显著差异。相关分析结果表明：菌根侵染率与根鲜重、根总长、根表面积、根体积、根分枝数、根尖数呈极显著正相关（P < 0.001），与拓扑指数、根比例呈极显著负相关（P < 0.001）。研究表明，在干旱条件下，AMF虽然没有提高生长初期的根系的吸收效率，但接种AMF显著影响幼苗根系形态特征和结构特征，更利于植物适应干旱环境，并且AMF对幼苗根系的促生作用随着干旱胁迫程度减轻而提高。 Abstract:Arbuscular mycorrhizal fungi (AMF) can develop a symbiotic relationship with the roots of most terrestrial plants, which can improve the drought tolerance of the host plants. Based on our previous studies, AMF play a critical role in promoting native plant growth in the arid valley of the Minjiang River, China. Furthermore, the effects of AMF on root growth are as important as their effects on aboverground growth. To understand how plant roots respond to AMF under different drought stress conditions, we designed a completely randomized full factorial pot experiment in a greenhouse in the arid valley of the Minjiang River. We added one common AMF (Funneliformis mosseae, FM) to the roots of seedlings from a dominant native shrub (Bauhinia faberi var. microphylla), using three different drought stress conditions. Continuous drought stress was induced by watering the seedlings with distilled water at one-day intervals for three months at low (40%), medium (60%), and high levels (80%) of the field capacity. At the end of the experiment, we harvested the seedlings, and cleaned their roots with distilled water. We subsequently measured the root fresh weight, scanned the roots with a root scanner (EPSON 11000XL), and obtained variables such as root length, root surface area, root volume, root forks, and number of root tips with WinRhizo. We subsequently analyzed the root architecture and the functional characteristics of the B. faberi seedlings to address the relationship between root development and AMF presence under different levels of drought stress. We used one-way ANOVAs, two-way ANOVAs, LSD fitting methods, and Pearson's correlations for our statistical analyses. Inoculation of FM significantly increased the total root length, root surface area, root forks, and the number of root tips under all three drought stress conditions (P < 0.001). In addition, under medium and high soil water content, it significantly increased root fresh weight and root volume (P < 0.001). More specifically, high soil water conditions resulted in the significantly highest root fresh weight, total root length, root surface area, root volume, and number of root tips after FM addition. Nonetheless, there was no significant difference in average root diameter between inoculated and non-inoculated seedlings. Inoculated seedlings tended to develop a dichotomous branching style, which was more profound at low (40% of field capacity) soil water content (P < 0.001). Furthermore, the root fractions of inoculated seedlings were significantly smaller than the non-inoculated seedlings (P < 0.001). However, there was no significant difference in specific root length among all the treatments. Root fresh weight, root length, root surface area, root volume, root forks, and number of root tips correlated significantly and positively with colonization rate (P < 0.001). In contrast, topological index and root fraction were significantly and negatively correlated with colonization rate (P < 0.001). Overall, we found that, although AMF did not improve the root absorption efficiency in the initial growth period of B. faberi, AMF presence significantly affected seedling root morphology and root functional characteristics. These latter effects enhanced B. faberi seedling growth, which allowed the plants to adapt to drought conditions. Finally, the positive effects of AMF on root growth increased with improving water conditions. 参考文献 相似文献 引证文献

INFLUENCE OF PLOUGHING DEPTH, PHOSPHORUS FERTILIZER LEVEL AND THINNING DATE ON SUGAR BEET PRODUCTIVITY AND QUALITY

This investigation was conducted at El-Manyal Village, Talkha District, Dakahlia Governorate, during 2012/2013 and 2013/2014 seasons to study the effect of ploughing depth (0.0, 10, 20 and 30 cm), phosphorus fertilizer levels (0.0, 15.5 and 31.0 kg P2O5/fad) and thinning dates (at 20, 30 and 40 days after sowing) on productivity and quality of sugar beet variety Kawemira. A split-plot design with four replicates was used for each ploughing depth during the two seasons (each ploughing depth was considered as a separate experiment). The main results of this investigation could be summarized as follows: 1- Increasing ploughing depths from 0.0 up to 30 cm significantly increased root fresh weight, root length, total soluble solids percentage (TSS %) as well as root and sugar yields/faddan. On the other hand, it significantly decreased root juice purity percentage in both seasons. 2- Increasing phosphorus fertilizer levels from 0.0 to 15.5 and 31.0 kg P2O5/fad, significantly increased all studied characters in both seasons. 3- Delaying thinning dates from 20 to 30 and 40 days after sowing markedly decreased all studied characters, except root diameter in both seasons. 4- The interactions among studied factors showed insignificant effects, except for the effect of the interaction between ploughing depth and phosphors fertilizer levels on root length in the first season and sugar yield/fad in the second season. Increasing ploughing depth to be 30 cm, adding 31.0 kg P2O5/fad and thinning at the age of 20 days was the suitable recommendation to maximize sugar beet root yield and quality under the environmental conditions of Dakahlia Governorate.

EFFECT OF NITROGEN FERTILIZATION AND HARVESTING DATES ON SUGAR BEET PRODUCTIVITY AND QUALITY IN NEWLY RECLAIMED SANDY SOILS

Two field experiments were carried out at Kalabsho Experimental Farm, Dakahlia Governorate, Sugar Crops Research Institute, Agricultural Research Center, during 2009/2010 and 2010/2011 seasons, to evaluate the effect of nitrogen fertilizer levels (100, 120, and 140 kg N/fad), three split applications of nitrogen fertilizer (two, three and four equal doses) and harvesting dates (180, 195 and 210 days after sowing) on productivity and quality of sugar beet cv. Gazelle. Increasing nitrogen fertilizer levels from 100 to 140 kg N/fad significantly increased root fresh weight, root length and diameter, root and sugar yields/fad in both seasons. The inverse was true in total soluble solids (TSS), sucrose and purity percentages in both seasons. Splitting nitrogen fertilizer from 2 to 4 equal doses significantly increased root fresh weight, root length and diameter, TSS %, purity % and root and sugar yields/fad in both seasons. On the other hand, it decreased sucrose % in both seasons. Delaying harvesting date from 180 to 210 days after sowing significantly increased all studied characters, except for root juice purity in both seasons. Splitting 140 kg N/fad into four equal doses and harvesting at 210 days after sowing are the suitable treatment to maximize sugar beet productivity and quality under the environmental conditions of the newly reclaimed sandy soils of Kalabsho region, Dakahlia Governorate.

Arabidopsis LOS5 Gene Enhances Chilling and Salt Stress Tolerance in Cucumber

Low temperature and high salinity are the major abiotic stresses that restrict cucumber growth and production, breeding materials with multiple abiotic resistance are in greatly need. Here we investigated the effect of introducing the LOS5 gene, a key regulator of ABA biosynthesis in Arabidopsis thaliana, under the stress-responsive RD29A promoter into cucumber (Cucumis sativus L. cv. S516). We found that T1RD29A-LOS5 transgenic lines have enhanced tolerance to cold and salt stresses. Specifically, transgenic lines exhibited dwarf phenotypes with reduced leaf number, shorter internode, decreased length of the biggest leaf, fewer female flowers, shorter fruit neck and lower vitamin C (Vc). The increased cold tolerance can be reflected from the significantly decreased cold index, the reduced electrolyte leakage index and the MDA content upon cold treatment as compared to those in the control. This may result from the accumulation of internal ABA, soluble sugars and proline, and the enhanced activities of protective enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the transgenic lines. Under salt treatment, the transgenic lines exhibited increased germination index, vigor index, more lateral roots and increased root fresh weight. Moreover, RD29A-LOS5 transgenic plants displayed quicker responses in salt stress than that in low-temperature stress.

EVALUATION OF SOME SUGAR BEET VARIETIES AS AFFECTED BY HARVESTING DATES UNDER NEWLY RECLAIMED SOIL

Two field experiments were carried out during 2008/2009 and 2009/2010 seasons at Kafr El-Hammam village, Sharkia Governorate to study the effect of harvesting dates on productivity of some sugar beet varieties. Sugar beet varieties Gazella, Carola and Lola were planted on 1st October in both seasons. Harvesting dates were done at 180, 195 and 210 days from sowing. The experimental design was a split-plot design with four replication, harvesting dates were allocated in the main plots and varieties in the sub-plots. Results showed that: delaying harvesting dates from 180 to 210 days from sowing significantly increased root fresh weight (g/plant), sucrose%, as well as root and sugar yield (tons/fed). While, nitrogen%, sodium%, potassium% were decreased significantly in both seasons. Harvesting dates at 195 days from sowing gave the highest values. Sugar beet varieties gave significant increase for root fresh weight (g/plant), sucrose%, as well as, root yield and sugar yield (tons/fed) in both seasons. While, sodium%, potassium% decreased significantly in both seasons. However, root diameter in the 2nd season only. The interaction was significant in both seasons for root fresh weight (g/plant), sucrose%, root and sugar yield (tons/fed). However, root diameter in the 1st season and sodium and potassium% in the 2nd season., respectively. In general it can be concluded that harvesting Lola sugar beet variety at 195 days from sowing was the best treatment for maximizing sugar beet productivity in the newly reclaimed soils under the environment of this study.

Productivity of fodder beet (Beta vulgaris var.Crassa) cultivars affected by nitrogen and plant spacing

A field experiment was conducted in the (2007/08 – 2008/09) seasons to study the effects of nitrogen fertilization and plant spacing on yields and its components of three fodder beet cultivars. The experiment was a randomized complete block design (RCBD) in split-split plots arrangement. Nitrogen treatments at a rate of 0, 40, 80 and 120 kg N/ha were assigned to the main plots applied eleven days from planting. Plant spacing (15, 20 and 25 cm between holes) and fodder beet cultivars (Voroshenger, Anisa and Polyproductiva) were allotted to the sub and sub-sub-plots, respectively. Nitrogen application increased root fresh weight; dry weights of shoot, root; green and dry fodder yields significantly (p<0.05) in the first season. Nitrogen had no significant effects on shoot fresh weight. Wider spacing significantly (p<0.05) increased root dry weight in the first season. Green and dry fodder yields were significantly (p<0.05) increased under closer spacing in the second season. Spacing had no significant effects on root fresh weight, shoot fresh weight, and shoot dry weight. Cultivars exhibited highly significant (p<0.01) differences in shoot dry weight in both seasons. Cultivars affected shoot fresh weight significantly (p<o.o5) in the first season and highly significantly (p<0.01) in the second one. Fresh and dry weight of root, green and dry fodder yields were not significantly affected by cultivars. Shoot dry weight was significantly greater under higher nitrogen levels and wider spacing (N2S2and N3S3) in the second season. Nitrogen and cultivars interaction resulted in significant (p<0.05) increase in root dry weight attained by Voroshenger and Polyproductiva cultivars under 80 kg/N/ha (N2V1 and N2V3) in the first and second season, respectively. Polyproductiva sown at 25cm apart (S3V3) significantly (p<0.05) attained the greatest root dry weight in the second season.