Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.

Leaf endophyte Neotyphodium coenophialum modifies mineral uptake in tall fescue

Abstract: Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E- plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E- plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E- plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E- plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E- plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E- DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency.

Growth, nitrogen fixation and ammonium assimilation in common bean (Phaseolus vulgaris): effect of phosphorus

Abstract: The impact of phosphorous nutrition on plant growth, symbiotic N 2 fixation, ammonium assimilation, carbohydrate and aminoacid accumulation, as well as on nitrogen, phosphorus and ATP content in tissues in common bean (Phaseolus vulgaris) plants was investigated. Plants inoculated with Rhizobium tropici CIAT899 were grown in Leonard jars under controlled conditions, with P-deficient (0 and 0.1 mM), P-medium (0.5, 1 and 1.5 mM) and P-high (2 mM) conditions in a N-free nutrient solution. The P application, increased leaf area, whole plant DW (67%), nodule biomass (4-fold), and shoot and root P content (4- and 6-fold, respectively) in plant harvested at the onset of flowering (28-days-old). However, P treatments decreased the total soluble sugar and amino acid content in vegetative organs (leaf, root and nodules). The root growth proved less sensitive to P deficiency than did shoot growth, and the leaf area was significantly reduced at low P-application. The absence of a relationship between shoot N content, and P levels in the growth medium could indicate that nitrogen fixation requires more P than does plant growth. The optimal amount for the P. vulgaris-R. tropici CIAT899 symbiosis was 1.5 mM P, this treatment augmented nodule-ARA 20-fold, and ARA per plant 70-fold compared with plants without P application.

The influence of vesicular-arbuscular mycorrhiza on growth and water relations of red clover

Abstract: Summary Vesicular-arbuscular (VA) mycorrhizal infection of red clover grown in phosphate deficient soils enhanced the concentration of P in the tissues, stimulated growth of root and shoot but reduced the root/shoot ratio. Addition of phosphate to well below the optimum level also stimulated growth and enhanced P status of non-mycorrhizal plants, but their yields and P concentrations were much smaller than those of mycorrhizal plants and their root/shoot ratios were unaffected. The hydraulic conductivities of the root systems were very much higher in mycorrhizal than in uninfected plants. This could be partly attributed to the greater lengths and diameters and hence total surface areas of the mycorrhizal roots. Per unit length of root, the conductivities of the mycorrhizal roots were still two to three times higher, suggesting that this was mainly due to hyphal growth in the soil. When soil water was not limiting, the lower root resistances combined with larger leaf surface areas and possibly also lower leaf diffusion resistances resulted in very much higher transpiration rates and fluxes in mycorrhizal than in non-mycorrhizal plants. Under conditions of water stress, however, the leaf diffusion resistances of mycorrhizal plants were higher and transpiration fluxes lower compared with uninfected plants but, because of their higher total water demands, they wilted more rapidly. Mycorrhizal plants were able to extract soil moisture down to lower water potentials than non-mycorrhizal plants (difference about 1 MPa) but, possibly because of their lower leaf water potentials and higher root conductivities, they recovered turgor more rapidly than non-mycorrhizal plants when soil water was restored. Thus, the mycorrhizal habit is an advantage to the host plant in times of moisture stress.

Induction of Heat Stress Tolerance in Barley Seedlings by Pre-Sowing Seed Treatment with Glycinebetaine

Abstract: Heat stress adversely affects plant growth and development, while glycinebetaine (GB) plays a protective role under stressful conditions. The objective of this study was to assess the optimum level of GB for use as a presowing seed treatment and the subsequent effect on the heat tolerance of barley (Hordeum vulgare L. cv. Haider-93) seedlings. Among a range of GB levels, the 20 mM concentration emerged as the most effective in enhancing seed germination, shoot fresh and dry weight and shoot water content under heat stress, and this level was selected for further studies. Time course changes revealed that the seedlings developing from 20 mM GB treated seeds had greater shoot dry weight, net photosynthetic rate (PN), leaf water potential (ψw) and reduced relative membrane permeability (RMP), compared to no-GB treated plants under heat stress. Correlations between dry weight and high PN (r = 0.881), low ψw (r = −0.938) and RMP (r = −0.860) of shoots suggested the involvement of GB in heat stress tolerance. Leakage of Ca2+ and NO3− was the greatest followed by K+ and PO43− under no-GB seed treatment, and GB application under heat stress appreciably reduced the leakage of all these ions, particularly Ca2+, K+ and NO3−. In conclusion GB absorbed by seeds, after translocation to the seedlings, enhanced their capacity to maintain greater water content, and higher seedling vigor by virtue of increased PN, reduced RMP and leakage of important ions under heat stress. These results have implications for final field stand under the conditions where the ambient temperature is supra-optimal for barley growth.

Primary and secondary stem growth in arctic shrubs: implications for community response to environmental change

Abstract: Summary 1 Shrubs are among the tundra plants most responsive to environmental change We measured primary and secondary stem growth in a retrospective analysis of ramets of three codominant shrubs (Betula nana, Salix pulchra, and Ledum palustre ssp decumbens) exposed to long-term field treatment with greenhouses and N + P fertilizers at Toolik Lake, Alaska 2 Ramets of Salix had the greatest primary stem growth under control conditions, because of their relatively high branching rate Under fertilization, however, Betula produced much more primary stem growth than the other species, because axillary buds that would have grown as short shoots in control ramets were instead stimulated to produce long shoots (structural branches) There appeared to be a trade-off between allocation to length per stem segment and number of stem segments produced in a given year, for both Betula and Ledum 3 Although secondary growth in stems is the largest component of above-ground net primary production in forests, it is often ignored in shrub-dominated ecosystems We derived an expression for secondary growth in shrubs based on distributions of stem mass and length with age, and allowing for experimentally induced changes in secondary growth rate 4 There was good agreement between measured ramet stem mass and calculated values for all three species, validating our mathematical analysis of secondary growth 5 Fertilization greatly increased the relative rate of secondary growth only in Betula, consistent with observed accumulations of its stem mass in ecosystem-level quadrat harvests Secondary growth of Betula was a major component of ecosystem NPP in fertilized plots and probably contributes significantly to ecosystem carbon storage 6 The increase in its secondary growth enabled Betula to become dominant under fertilization, whereas the inability of older stems of Ledum to respond in this way prevented it from growing into the canopy