Dry Weight Of Whole Plant Research Articles

Leaf sodium homeostasis controlled by salt gland is associated with salt tolerance in mangrove plant Avicennia marina.

Avicennia marina, a mangrove plant growing in coastal wetland habitats, is frequently affected by tidal salinity. To understand its salinity tolerance, the seedlings of A. marina were treated with 0, 200, 400 and 600mM NaCl. We found the whole-plant dry weight and photosynthetic parameters increased at 200mM NaCl but decreased over 400mM NaCl. The maximum quantum yield of primary photochemistry (Fv/Fm) significantly decreased at 600mM NaCl. Transmission electron microscopy observations showed high salinity caused the reduction in starch grain size, swelling of the thylakoids and separation of the granal stacks, and even destruction of the envelope. In addition, the dense protoplasm and abundant mitochondria in the secretory and stalk cells, and abundant plasmodesmata between salt gland cells were observed in the salt glands of the adaxial epidermis. At all salinities, Na+ content was higher in leaves than in stems and roots; however, Na+ content increased in the roots while it remained at a constant level in the leaves over 400mM NaCl treatment, due to salt secretion from the salt glands. As a result, salt crystals on the leaf adaxial surface increased with salinity. On the other hand, salt treatment increased Na+ and K+ efflux and decreased H+ efflux from the salt glands by the non-invasive micro-test technology, although Na+ efflux reached the maximum at 400mM NaCl. Further real-time quantitative PCR analysis indicated that the expression of Na+/H+ antiporter (SOS1 and NHX1), H+-ATPase (AHA1 and VHA-c1) and K+ channel (AKT1, HAK5 and GORK) were up-regulated, and only the only Na+ inward transporter (HKT1) was down-regulated in the salt glands enriched adaxial epidermis of the leaves under 400mM NaCl treatment. In conclusion, salinity below 200mM NaCl was beneficial to the growth of A. marina, and below 400mM, the salt glands could excrete Na+ effectively, thus improving its salt tolerance.

ALLEVIATION OF CHANGES IN GROWTH AND PHYSIOCHEMICAL PARAMETERS IN SALT (NACL) STRESSED OF TWO SESAME (SESAMUM INDICUM L) VARIETIES

Present research was carried out with the aim of identifying effect of salt stress (NaCl 0(Control), 40, 80, and 120 mM) on growth and physiochemical parameters of sesame (Sesamum indicum L.) variety CO-1 and KRR-2. Various parameters such as height of the plant, leaf area, fresh weight of the whole plant and dry weight of whole plant and decreased the content of physiochemical parameters were analyzed. All the parameters were recorded at 30th Days after Treatment (DAT). Analysis revealed a significant reduction in all parameters with increased salt concentration. This experiment carried out fully pot culture methods. Severity of salinity stressed condition were also observed with increased salinity concentration level at the same time decrease in all growth parameter were non-significant in stressed plant as compared two sesame varieties CO-1 and KRR-2. CO-1 in the sesame varieties at 120mM high salt concentration increased with lower decreased was observed in height of the plant, Leaf area, fresh weight of the whole plant and dry weight of whole plant and decreased the content of physiochemical parameters compared to other sesame varieties KRR-2 under salt stress condition. The results indicated that plants of sesame variety CO-1 exhibited higher adaptive potential under salinity stress as judged by higher growth and higher content of physiochemical parameters when compared to variety KRR-2.

Developing Functional Relationships between Soil Waterlogging and Corn Shoot and Root Growth and Development.

Short- and long-term waterlogging conditions impact crop growth and development, preventing crops from reaching their true genetic potential. Two experiments were conducted using a pot-culture facility to better understand soil waterlogging impacts on corn growth and development. Two corn hybrids were grown in 2017 and 2018 under ambient sunlight and temperature conditions. Waterlogging durations of 0, 2, 4, 6, 8, 10, 12, and 14 days were imposed at the V2 growth stage. Morphological (growth and development) and pigment estimation data were collected 15 days after treatments were imposed, 23 days after sowing. As waterlogging was imposed, soil oxygen rapidly decreased until reaching zero in about 8–10 days; upon the termination of the treatments, the oxygen levels recovered to the level of the 0 days treatment within 2 days. Whole-plant dry weight declined as the waterlogging duration increased, and after 2 days of waterlogging, a 44% and 27% decline was observed in experiments 1 and 2, respectively. Leaf area and root volume showed an exponential decay similar to the leaf and root dry weight. Leaf number and plant height were the least sensitive measured parameters and decreased linearly in both experiments. Root forks were the most sensitive parameter after 14 days of waterlogging in both experiments, declining by 83% and 80% in experiments 1 and 2, respectively. The data from this study improve our understanding of how corn plants react to increasing durations of waterlogging. In addition, the functional relationships generated from this study could enhance current corn simulation models for field applications.

Differentially expressed microRNAs that target functional genes in mature soybean nodules.

MicroRNAs (miRNAs) are important regulators of biological functions in plants. To find out what roles miRNAs play in regulating symbiotic nitrogen fixation (SNF) in soybean [Glycine max (L.) Merr.], we identified high-confidence differentially expressed (DE) miRNAs from uninoculated roots (UR), rhizobium-inoculated roots (IR), and nodules (NODs) of soybean by robust small RNA sequencing (sRNA-seq). Based on their predicted target messenger RNAs (mRNAs), the expression profiles of some of these DE miRNAs could be linked to nodule functions. In particular, several miRNAs associated with nutrient transportation genes were differentially expressed in IRs and mature NODs. MiR399b, specifically, was highly induced in IRs and NODs, as well as by inorganic phosphate (Pi) starvation. In composite soybean plants overexpressing miR399b, PHOSPHATE2 (PHO2), a known target of miR399b that inhibits the activities of high-affinity Pi transporters, was strongly repressed. In addition, the overexpression of miR399b in the roots of transgenic composite plants significantly improved whole-plant Pi and ureide concentrations and the overall growth in terms of leaf node numbers and whole-plant dry weight. Our findings suggest that the induction of miR399b in NODs could enhance nitrogen fixation and soybean growth, possibly via improving Pi uptake to achieve a better Pi-nitrogen balance to promote SNF in nodules.

Application of Central Composite Design on Assessment and Optimization of Ammonium/Nitrate and Potassium for Hydroponically grown Radish (Raphanus sativus)

Central composite design and response surface methodology were applied to model bulb fresh weight, bulb dry weight, and whole-plant dry weight, based on ammonium/nitrate and potassium in nutrient solution for hydroponically grown radish between November and December in New Zealand. Three high-precision second-order models were developed. The R2 values were more than 0.90, Pre R2 values were reasonable, and Adeq Precision values were more than 10. The contributions of the two factors to the response variables were studied, and optimal nutrition was discussed using these models. Both factors affected the three response variables significantly and nonlinearly (all p values < 0.05). Ammonium/nitrate played a more important role than potassium in bulb fresh weight (p = 0.00 versus p = 0.01). The negative or positive influence of one factor on bulb fresh weight and whole-plant dry weight depended on the concentration of ammonium/nitrate and potassium. Nutrient solutions with ammonium/nitrate 4:11 (0.36) and potassium 5.6 mM, and with ammonium/nitrate 5:10 (0.50) and potassium 6.0 mM were both better than those of Hoagland and Anrnon for hydroponically Summer-grown radish in New Zealand.

In vitro morphophysiological screening of drought-tolerant potato genotypes

Sixteen potato genotypes were assessed for drought tolerance through morphophysiological characteristics using stress tolerance trait index (STTI), principal component analysis (PCA), and cluster analysis (CA). Two to three wk old nodal segments explants (1.0 to 2.0 cm long) derived from in vitro grown sprouts were cultured on MS medium that contained with different concentrations of sorbitol. After 6 wk of culture initiation, the length of shoots, roots, and internodes; thickness of shoot and roots; number of leaves and roots; fresh and dry weight of whole plant; and water content of plants were recorded. For PCA, the cultivars Arun, Granola, Surjomukhi, Sheelbilati, Jamalu, Chollisha, Patnai, and Dohazari showed relatively higher values regarding drought tolerance and Diamant, Asterix, Courage, Cardinal, Lalpakri, Sindurkouta, Ausha, and Sadaguti were drought-sensitive cultivars. For cluster analysis, the cultivars Arun, Granola, and Surjomukhi showed high tolerances to drought and Diamant was sensitive. Analysis of variance (ANOVA), Duncan’s multiple range test (DMRT), and correlation coefficient for different morphological and physiological traits showed significantly higher values at p < 0.01 level among the tested genotypes. The protocols standardized under this study may be helpful for plant breeders and biotechnologist to develop mass production of potato seeds/tubers in drought-prone areas.

Effects of fertilization levels on growth performance of micro-propagated &lt;em&gt;Cryptocoryne wendtii&lt;/em&gt; (Water Trumpet)

This study was conducted to evaluate the effects of different fertilization levels on growth performance of micro propagated water trumpet, Cryptocoryne wendtii to find the most suitable hardening medium. Micro-propagated ninety-six individual plants potted in the commonly used substrate of coir particles were used for the experiment and subjected to different fertilization levels of Albert’s solution. Plants were potted just after being taken from the vessels and eight plant pots kept in the tanks (25.5 L water) containing 0.5 gL–1, 1.0 gL–1, and 2.0 gL–1 of Albert’s solution, and fertilizer was not added into the control. Each treatment and control had three replicates and the experiment was conducted for nine weeks under natural light and temperature conditions. At the end of the experiment, plant growth performance in terms of plant height, root height, number of leaves etc. and water quality parameters were compared in One Way Analysis of Variance using SPSS (16.0). The electrical conductivity (EC) of the 0, 0.5, 1.0, 2.0 gL–1 treatments were 0.075, 0.75, 1.5, 3.0 µS/m, respectively. At the end of the experiment, plants grown in 0.5 gL–1 showed the best growth performance giving significantly highest plant height (11.77 ± 0.40 cm), root height (5.77 ± 0.03 cm), number of leaves (10.0 ± 0.3), number of roots (8.3 ± 0.3), wet weight of whole plant (0.3180 ± 0.0200 g), dry weight of whole plant (0.0206 ± 0.0003 g) and the largest leaf area (2.54 ± 0.01 cm2) in compared to other two treatments and control. In contrast, the uptake of Albert’s solution significantly increased with the increasing EC level. The results of this study revealed that, 0.5 gL–1 Albert’s solution is the most suitable fertilization level among tested three fertilization levels for the hardening process of micro-propagated C. wendtii.

Symbiotic Performances of Three Mesorhizobium huakuii Strains Inoculated to Chinese Milk Vetch Varieties.

In this experiment, 4 varieties of Chinese milk vetch (Xinyang, Minzi No. 6, Minzi 8487711, and Shishou) were used as host plants and inoculated with 3 strains of rhizobium (CCBAU 2609, M. h 93, and 7653R). The differences in their morphology, yield, and nodule characteristics at different growth stages were studied and the reasons for these differences were analyzed to explore the exclusivity between different varieties of Chinese milk vetch and strains of rhizobium. Results showed no significant difference in plant height and whole-plant dry weight at seedling stage under different treatments but significant differences in these characteristics at full flowering stage. The results indicated that Minzi 8487711 and Shishou were significantly better than the other varieties. During the whole growth period, the growth indexes and nodule characteristics of the 4 varieties inoculated with strain 7653R were better than those of the varieties inoculated with other strains. At full flowering stage, compared with that of the control group, the biomasses of Xinyang, Minzi No.6, Minzi 8487711, and Shishou had increased by 2.04, 2.84, 1.56, and 2.69-fold, respectively, and nitrogenase activities increased by 3.82, 9.60, 6.21, and 15.18%, respectively. Significant differences in the exclusivity between varieties and strains were observed. Minzi No.6–7653R and Shishou variety–7653R had the strongest exclusivity. The results showed that 7653R was a broad-spectrum and high-efficiency rhizobium strain. 7653R is recommended to be used in combination with Chinese milk vetch varieties, such as Minzi 8487711 and Shishou, to obtain advantages in yield and nitrogen fixation in production.

Effect of Phosphorus Fertilization and Psb on Garlic Quality under Organic Farming System

The present investigation was undertaken in complete randomized design with three replicates during winter season of 2017/2018 to study the effect of phosphorus fertilization (50, 75 and 100 % from recommended dose), Phosphate Solublizing Bacteria (PSB) and chicken manure on growth criteria , chemical traits, bulb quality and yield of garlic plants. The findings showed that growth criteria such as plant height, No. of leaves, fresh and dry weight of whole plant and its leaves, neck and bulb, yield and its components (number of clovers/bulb, bulb diameter, neck diameter, average cloves and bulb as well as total Mg/fed), chemical content (N, P and K %) and quality parameters (TSS%, total carbohydrates, crude fiber, vitamin C, dry matter, volatile oil and allicin) as well as availability of N, P and K recorded the highest values with plant treated with 75% P fertilization+ PSB +Chicken manure.

In vitro screening for salt stress tolerance of native and exotic potato genotypes by morphological and physiological parameters

This study was performed on in vitro bioassay screening for salt tolerance of ten native and six exotic potato genotypes in Bangladesh. Single node was used to evaluate salinity tolerance especially on biomass production. Five different concentrations of NaCl (0 = control, 100, 150, 200 and 250 mM) were used in addition to MS medium and evaluated salt tolerant and sensitive genotype by various morphological and physiological parameters e.g. shoot and root length and its thickness, number of leaves and roots, fresh and dry weight of whole plant and water contents. The ANOVA, DMRT and correlation coefficient were found highly significant at p&lt;0.01 among the genotypes. With salt stress condition highly positive correlation, co-efficient were found between stem length and internodal distance, leaves number, roots number, root length, dry weight of whole plant and fresh weight of whole plant. A dendrogram based on relative values of 10 morphological and physiological parameters of growth under salt conditions were led to clustering into four distinct group’s i.e. tolerant, moderately tolerant, sensitive and very sensitive. On the basis of stress tolerance trait indices (STTIs), Arun (92.78) and Ausha (80.27) showed as a highest salt tolerant, Jamalu (56.33) and Chollisha (57.03) showed the most salt sensitive potato cultivars. From this finding it may be concluded that in vitro screening with bioassay are relatively simple, rapid and convenient and these methods can be used for further advance biotechnological research on potato improvement.&#x0D; J. bio-sci. 28: 21-32, 2020

Hormonal regulation and redox reaction of maize under partial root drying irrigation

How three different irrigation regimes, conventional irrigation (CI), partial root drying (PRD), and deficit irrigation (DI), on endogenous hormonal abscisic acid (ABA) and zeatin-riboside (ZR) changes, stomatal conductance (gs), reactive oxygen species (ROS), antioxidant enzyme activities, and metabolism of non-enzymatic compounds was assessed. This investigation revealed that the root-sourced chemical signals induced by PRD irrigation reduced the gs without any altered relative water content (RWC) in leaves, and further analysis found that stress-triggered ABA could induce stomatal closure; however, ZR exhibited antagonistic effects on the accumulation and stomatal regulation of ABA. Thus, in the current study, gs was more responsive to the combined ABA/ZR signal than ABA signal solely. Both PRD and DI treatments increased the production rate of superoxide anion ( $$ {\text{O}}_{2}^{ \bullet - } $$ ) as well as hydrogen peroxide (H2O2) concentration in root and leaf tissues under stress conditions; however, the superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities significantly increased under PRD irrigation. Moreover, compared with DI regime, PRD irrigation caused less proline and malondialdehyde (MDA) accumulation in stressed root and leaf tissues, suggesting that PRD irrigation technique alleviated the stress-induced physiological damage. Consequently, compared to CI, the leaf area and whole-plant dry weight in maize were unchanged under PRD irrigation but reduced significantly under DI treatment.

Interaction of Huanglongbing and Foliar Applications of Copper on Growth and Nutrient Acquisition of Citrus sinensis cv. Valencia

The following study was conducted in 2016 and 2017 to determine the impact of frequent foliar copper (Cu) applications on Huanglongbing (HLB)-affected Citrus sinensis cv. Valencia orange. The experiment was conducted in a psyllid-free greenhouse with HLB-positive and non-HLB control trees grown in an Immokalee fine sand soil. The trees were well-maintained to promote health. Cu was applied to the foliage at 0x, 0.5x, 1x, and 2x the commercially recommended rates, which were 0, 46, 92, and 184 mm, respectively, with applications made 3x in both 2016 and 2017. The impact of HLB and Cu treatments on leaf and root Cu concentrations, vegetative growth, Candidatus Liberibacter asiaticus (CLasiaticus) genome copy number, and acquisition of other essential nutrients were determined. HLB caused the roots to acidify the soil more than non-HLB controls, which promoted Cu availability and promoted greater Cu concentrations in leaves and roots. HLB and Cu application treatments suppressed leaf area and total root length observable in rhizotron tubes such that, by the end of the experiment, leaf, stem, root, and whole-plant dry weights were reduced. HLB reduced foliar concentrations of calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn) and possibly iron (Fe), but HLB did not affect root concentrations of these same essential nutrients. Cu application treatments did not affect leaf or root concentrations of other essential nutrients except foliar concentration of Fe, which may have been suppressed. Foliar applications of Cu are used to suppress Xanthomonas citri ssp. citri (Xcc) the causal agent of citrus canker, and the frequency of its use may need to be reconsidered in commercial groves.

Growth performance, organ-level ionic relations and organic osmoregulation of Elaeagnus angustifolia in response to salt stress.

Elaeagnus angustifolia is one of the most extensively afforested tree species in environment-harsh regions of northern China. Despite its exceptional tolerance to saline soil, the intrinsic adaptive physiology has not been revealed. In this study, we investigated the growth, organ-level ionic relations and organic osmoregulation of the seedlings hydroponically treated with 0, 100 and 200 mM NaCl for 30 days. We found that the growth characteristics and the whole-plant dry weight were not obviously stunted, but instead, were even slightly stimulated by the treatment of 100 mM NaCl. In contrast, these traits were significantly inhibited by 200 mM NaCl treatment. Interestingly, as compared with the control (0 mM NaCl), both 100 and 200 mM NaCl treatments had a promotional effect on root growth as evidenced by 26.3% and 2.4% increases in root dry weight, respectively. Roots had the highest Na+ and Cl- concentrations and obviously served as the sink for the net increased Na+ and Cl-, while, stems might maintain the capacity of effective Na+ constraint, resulting in reduced Na+ transport to the leaves. K+, Ca2+ and Mg2+ concentrations in three plant organs of NaCl-treated seedlings presented a substantial decline, eventually leading to an enormously drop of K+/Na+ ratio. As the salt concentration increased, proline and soluble protein contents continuously exhibited a prominent and a relatively tardy accumulation, respectively, whereas soluble sugar firstly fell to a significant level and then regained to a level that is close to that of the control. Taken together, our results provided quantitative measures that revealed some robust adaptive physiological mechanisms underpinning E. angustifolia’s moderately high salt tolerance, and those mechanisms comprise scalable capacity for root Na+ and Cl- storage, effectively constrained transportation of Na+ from stems to leaves, root compensatory growth, as well as an immediate and prominent leaf proline accumulation.

Abiotic stress tolerance and ABA responses of transgenic Glycine max plants with modulated RACK1 expression

The receptor for activated C kinase 1 (RACK1) belongs to a protein subfamily that contains a tryptophan-aspartic acid-domain (WD) repeat structure. In this study, a soybean RACK1 gene (GmRACK1) was cloned. The amino acid sequence of GmRACK1 had seven WD repeats, which contained typical glycine-histidine (GH) and WD dipeptides. Tissue-specific expression showed that GmRACK1 is expressed at differential levels in all examined tissues and strongly down-regulatd by abscisic acid (ABA) and abiotic stress. Subcellular localization suggested that GmRACK1 is located in the plasma membrane, cytoplasm, and nucleus. In response to drought and salt stress, the GmRACK1-RNAi lines showed significantly higher dry weight of whole plants, chlorophyll content, and survival rate of soybean seedlings than wild-type and homozygous (OE) lines. GmRACK1-RNAi plants were observed to be more sensitive to ABA-mediated seed germination and root growth. Furthermore, we found that the level of ABA and transcript levels of stress-responsive genes were clearly up-regulated under drought and salt stress conditions in GmRACK1-RNAi plants. Consistent with the accumulation of reactive oxygen species (ROS), elevated electrolyte leakage and malondialdehyde, and lower expression of ROS-scavenging genes were found in the GmRACK1-OE lines. The GmRACK RNAi lines exhibited increased tolerance to drought and salt stress compared with the wild-type and OE lines. In addition, yeast two-hybrid assays showed that GmRACK1 could interact with WNK8, eIF6, and RbohC-N. These results therefore indicate that GmRACK1 responds to drought and salt stress through ABA signaling and the regulation of cellular ROS production in plants.

Effect of Presoaking Sugar Beet (Beta vulgaris L.) Seeds with Gibberellic, Abscisic or Ascorbic Acids on Alleviation of Salinity Stress

A study was conducted to investigate the effect of presoaking of sugar beet (Beta vulgaris L.) seeds (polygerm) with gibberellic acid, abscisic acid, or ascorbic acid on alleviation of salt stress at seedling stage. The salinity levels of irrigation solution were 0, 25, 50 and 100 mM NaCl and the presoaking treatments were water as a control, 10 µM GA3, 10 µM ABA, and 0.5 mM ASA for 12 hrs. Seeds were sown in plastic pot containing 0.8 Kg prewashed sand and irrigated three times weekly by 100 mL per pot of one-tenth modified Hoagland solution containing the salt level. After seven weeks from sowing, the whole plants were collected. The results indicated that increasing salt concentration decreased the fresh and dry weight of whole plant, shoot and root, and shoot height of all presoaking treatments. However, shoot/root ratio on fresh and dry weight basis and moisture content of whole plant, shoot and root, chlorophyll content index, and electrolyte leakage were increased with increasing salt concentration of all presoaking treatments. However, presoaking of sugar beet seeds (polygerm) with the GA3, ABA, or ASA showed no significant effect to alleviation salt stress on sugar beet seedlings. However, the interaction between salt levels and presoaking treatments was significant for whole plant and root fresh and dry weights, shoot/root ratio on fresh weight basis, whole plant and root moisture content and chlorophyll content index, while nonsignificant for shoot fresh and dry weights, shoot height, shoot/root ratio on dry weight basis, shoot moisture content and electrolyte leakage.

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In the present study the plant materials of water hyacinth (Eichornia crassipes) and water lettuce (Pistia stratiotes) were collected from Aranmanai Kulam Dindigul (Dt), Tamilnadu, India, and carefully brought into the laboratory. Then the fresh and dry weight of whole plant, leafs, stems and roots of water hyacinth and water lettuce were analyzed. After that the Carbon, Nitrogen, Cellulose, Hemicellulose, Lignin, Protein, Lipid, Ash and Calorific value were also analyzed. The results indicated that the Carbon, Nitrogen, Cellulose, Hemicellulose, Lignin, Protein, Lipid, Ash and Calorific value were significantly higher in, leafs, stems and roots of water hyacinth than in leaves and roots of water lettuce.

Integrated nutrient management on growth and yield of garlic under sodic wasteland conditions

An investigation was carried out to study the combined effect of PSB, Trichoderma and FYM with 100% recommended dose of NPK on plant growth and bulb yield of garlic under sodic wasteland condition. Significantly higher values of growth and yield parameters, i.e. plant height (60.7 cm), leaf length (22.43 cm), root length (7.84 cm), number of leaves per plant (9.2), bulb weight (52.43 g), number of cloves per bulb (37.66), dry weight of whole plant (53.24 g) and bulb yield (60.86 q ha−1) was obtained with the application of 100% recommended dose of NPK supplemented with the application of FYM and clove (seed) treatment with Trichoderma and PSB.

GmPHR1, a Novel Homolog of the AtPHR1 Transcription Factor, Plays a Role in Plant Tolerance to Phosphate Starvation

GmPHR1 from soybean (Glycine max) was isolated and characterized. This novel homolog of the AtPHR1 transcription factor confers tolerance to inorganic phosphate (Pi)-starvation. The gene is 2751 bp long, with an 819-bp open reading frame and five introns. Analysis of transcription activity in yeast revealed that the full-length GmPHR1 and its C-terminal activate the reporter genes for His, Ade and Ura, suggesting that the C-terminal peptide functions as a transcriptional activator. Quantitative real-time PCR indicated that patterns of GmPHR1 expression differed. For example, under low-Pi stress, this gene was quickly induced in the tolerant JD11 after 0.5 h, with expression then decreasing slowly before peaking at 12-24 h. By contrast, induction in the sensitive Niumaohuang (NMH) was slow, peaking at 6 h before decreasing quickly at 9 h. GmPHR1 showed sub-cellular localization in the nuclei of onion epidermal cells and Arabidopsis roots. Growth parameters in wild-type (WT) Arabidopsis plants as well as in overexpression (OE) transgenic lines were examined. Under low-Pi conditions, values for shoot, root and whole-plant dry weights, root to shoot ratios, and lengths of primary roots were significantly greater in OE lines than in the WT. These data demonstrate that GmPHR1 has an important role in conferring tolerance to phosphate starvation.

Common mycorrhizal networks amplify size inequality in Andropogon gerardii monocultures

Arbuscular mycorrhizal fungi can interconnect plant root systems through hyphal common mycorrhizal networks, which may influence the distribution of limiting mineral nutrients among interconnected individuals, potentially affecting competition and consequent size inequality. Using a microcosm model system, we investigated whether the members of Andropogon gerardii monocultures compete via common mycorrhizal networks. We grew A. gerardii seedlings with isolated root systems in individual, adjacent containers while preventing, disrupting or allowing common mycorrhizal networks among them. Fertile soil was placed within the containers, which were embedded within infertile sand. We assessed mycorrhizas, leaf tissue mineral nutrient concentrations, size hierarchies and the growth of nearest neighbors. Plants interconnected by common mycorrhizal networks had 8% greater colonized root length, 12% higher phosphorus and 35% higher manganese concentrations than plants severed from common mycorrhizal networks. Interconnected plants were, on average, 15% larger and had 32% greater size inequality, as reflected by Gini coefficients, than those with severed connections. Only with intact common mycorrhizal networks were whole-plant dry weights negatively associated with those of their neighbors. In the absence of root system overlap, common mycorrhizal networks likely promote asymmetric competition below ground, thereby exaggerating size inequality within A. gerardii populations.

Effects of Irradiance Level on the Growth and Photosynthesis of Salvia

Seedlings of Salvia coccinea, S. splendens and S. viridis were grown at 100, 50, 25 and 5% of full sunlight level to determine the influence of irradiance level on their grown and photosynthesis. For all species the shoot length and dry weight of wholeplant were decreased at 25% sunlight, but there was little defference in them between at 50 and 100% sunlight. Total leaf area tended to increase at 50% sunlight in S. splendens and S. viridis and to decrease at 25% sunlight in S.coccinea. Leaf area ratio increased with decreasing light intensity in every species, and the degree of increase was the least in S.coccinea. With decreasing light intensity, leaves became thinner and the specific leaf weight decreased for all species. Chlorophyll content and photosynthetic rate more decreased at 25% than those at 100 and 50% sunlight in S. splendens and S. viridis. There were little differences both in the chlorophyll content and photosynthesis among these light intensities in S.coccinea. This indicates that S.coccinea has higher adaptability to low irradiance than other two species. Under weak light condition the stomatal conductance increased for all species. At 5% sunlight, the plant dry weight was less than about 90% of that of 100% sunlight and photosynthetic rate almost decreased to the light compensation point.