Showing papers on "Shoot published in 2003"
TL;DR: MAX4 and RMS1 were found to encode orthologous, auxin-inducible members of the polyene dioxygenase family, suggesting that MAX4 is required to produce a mobile branch-inhibiting signal, acting downstream of auxin.
Abstract: Shoot branching is inhibited by auxin transported down the stem from the shoot apex. Auxin does not accumulate in inhibited buds and so must act indirectly. We show that mutations in the MAX4 gene of Arabidopsis result in increased and auxin-resistant bud growth. Increased branching in max4 shoots is restored to wild type by grafting to wild-type rootstocks, suggesting that MAX4 is required to produce a mobile branch-inhibiting signal, acting downstream of auxin. A similar role has been proposed for the pea gene, RMS1. Accordingly, MAX4 and RMS1 were found to encode orthologous, auxin-inducible members of the polyene dioxygenase family.
582 citations
TL;DR: It is concluded that OsTB1 functions as a negative regulator for lateral branching in rice, presumably through expression in axillary buds, as observed throughout the axillary bud, as well as the basal part of the shoot apical meristem, vascular tissues in the pith and the lamina joint.
Abstract: Although the shoot apical meristem (SAM) is ultimately responsible for post-embryonic development in higher plants, lateral meristems also play an important role in determining the final morphology of the above-ground part. Axillary buds developing at the axils of leaves produce additional shoot systems, lateral branches. The rice TB1 gene (OsTB1) was first identified based on its sequence similarity with maize TEOSINTE BRANCHED 1 (TB1), which is involved in lateral branching in maize. Both genes encode putative transcription factors carrying a basic helix-loop-helix type of DNA-binding motif, named the TCP domain. The genetic locus of OsTB1 suggested that OsTB1 is a real counterpart of maize TB1. Transgenic rice plants overexpressing OsTB1 exhibited markedly reduced lateral branching without the propagation of axillary buds being affected. We also demonstrated that a rice strain carrying a classical morphological marker mutation, fine culm 1 (fc1), contain the loss-of-function mutation of OsTB1 and exhibits enhanced lateral branching. Expression of OsTB1, as examined with a putative promoter-glucuronidase (GUS) gene fusion, was observed throughout the axillary bud, as well as the basal part of the shoot apical meristem, vascular tissues in the pith and the lamina joint. Taking these data together, we concluded that OsTB1 functions as a negative regulator for lateral branching in rice, presumably through expression in axillary buds.
532 citations
TL;DR: It is shown that ectopic expression of the mtlD gene for the biosynthesis of mannitol in wheat improves tolerance to water stress and salinity and concludes that the improved growth performance of calli and mature leaves was due to other stress-protective functions ofMannitol, although this study cannot rule out possible osmotic effects in growing regions of the plant.
Abstract: Previous work with model transgenic plants has demonstrated that cellular accumulation of mannitol can alleviate abiotic stress. Here, we show that ectopic expression of the mtlD gene for the biosynthesis of mannitol in wheat improves tolerance to water stress and salinity. Wheat ( Triticum aestivum L. cv Bobwhite) was transformed with the mtlD gene of Escherichia coli . Tolerance to water stress and salinity was evaluated using calli and T 2 plants transformed with (+mtlD) or without (−mtlD) mtlD . Calli were exposed to −1.0 MPa of polyethylene glycol 8,000 or 100 mm NaCl. T 2 plants were stressed by withholding water or by adding 150 mm NaCl to the nutrient medium. Fresh weight of −mtlD calli was reduced by 40% in the presence of polyethylene glycol and 37% under NaCl stress. Growth of +mtlD calli was not affected by stress. In −mtlD plants, fresh weight, dry weight, plant height, and flag leaf length were reduced by 70%, 56%, 40%, and 45% compared with 40%, 8%, 18%, and 29%, respectively, in +mtlD plants. Salt stress reduced shoot fresh weight, dry weight, plant height, and flag leaf length by 77%, 73%, 25%, and 36% in −mtlD plants, respectively, compared with 50%, 30%, 12%, and 20% in +mtlD plants. However, the amount of mannitol accumulated in the callus and mature fifth leaf (1.7–3.7 μmol g −1 fresh weight in the callus and 0.6–2.0 μmol g −1 fresh weight in the leaf) was too small to protect against stress through osmotic adjustment. We conclude that the improved growth performance of mannitol-accumulating calli and mature leaves was due to other stress-protective functions of mannitol, although this study cannot rule out possible osmotic effects in growing regions of the plant.
513 citations
TL;DR: It is suggested that the reduction in shoot development and leaf elongation were related to toxic ion accumulation and depletion of K+ ions in the leaf blades and the accumulation of organic solutes in leaves did not appear to be related to salt tolerance.
422 citations
TL;DR: Great nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.
Abstract: The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investigated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0 S m-1 solutions of 1 M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.
311 citations
TL;DR: Root inoculation led to contamination of the entire plant, indicating that the pathogens are capable of moving on or within the plant in the absence of competition, and Seed contamination by these pathogens was undetectable in the presence of the competitor, Enterobacter asburiae.
Abstract: Enteric pathogens, such as Salmonella enterica and Escherichia coli O157:H7, have been shown to contaminate fresh produce. Under appropriate conditions, these bacteria will grow on and invade the plant tissue. We have developed Arabidopsis thaliana (thale cress) as a model system with the intention of studying plant responses to human pathogens. Under sterile conditions and at 100% humidity, S. enterica serovar Newport and E. coli O157:H7 grew to 10(9) CFU g(-1) on A. thaliana roots and to 2 x 10(7) CFU g(-1) on shoots. Furthermore, root inoculation led to contamination of the entire plant, indicating that the pathogens are capable of moving on or within the plant in the absence of competition. Inoculation with green fluorescent protein-labeled S. enterica and E. coli O157:H7 showed invasion of the roots at lateral root junctions. Movement was eliminated and invasion decreased when nonmotile mutants of S. enterica were used. Survival of S. enterica serovar Newport and E. coli O157:H7 on soil-grown plants declined as the plants matured, but both pathogens were detectable for at least 21 days. Survival of the pathogen was reduced in unautoclaved soil and amended soil, suggesting competition from indigenous epiphytes from the soil. Enterobacter asburiae was isolated from soil-grown A. thaliana and shown to be effective at suppressing epiphytic growth of both pathogens under gnotobiotic conditions. Seed and chaff harvested from contaminated plants were occasionally contaminated. The rate of recovery of S. enterica and E. coli O157:H7 from seed varied from undetectable to 19% of the seed pools tested, depending on the method of inoculation. Seed contamination by these pathogens was undetectable in the presence of the competitor, Enterobacter asburiae. Sampling of 74 pools of chaff indicated a strong correlation between contamination of the chaff and seed (P = 0.025). This suggested that contamination of the seed occurred directly from contaminated chaff or by invasion of the flower or silique. However, contaminated seeds were not sanitized by extensive washing and chlorine treatment, indicating that some of the bacteria reside in a protected niche on the seed surface or under the seed coat.
290 citations
TL;DR: Total shoot Cd accumulated per plant was much more closely related to population Cd tolerance than Cd hyperaccumulation, indicating that metal tolerance may be the more important selection criterion in developing lines with greatest phytoremediation potential.
Abstract: Thlaspi caerulescens J. & C. Presl is a distinctive metallophyte of central and western Europe that almost invariably hyperaccumulates Zn to > 1.0% of shoot dry biomass in its natural habitats, and can hyperaccumulate Ni to > 0.1% when growing on serpentine soils. Populations from the Ganges region of southern France also have a remarkable ability to accumulate Cd in their shoots to concentrations well in excess of 0.01% without apparent toxicity symptoms. Because hyperaccumulation of Cd appears to be highly variable in this species, the relationship between Cd tolerance and metal accumulation was investigated for seven contrasting populations of T. caerulescens grown under controlled conditions in solution culture. The populations varied considerably in average plant biomass (3.1fold), shoot : root ratio (2.2-fold), Cd hyperaccumulation (3.5-fold), shoot : root Cd-concentration ratio (3.1-fold), and shoot Cd : Zn ratio (2.6-fold), but the degree of hyperaccumulation of Cd and Zn were strongly correlated. Two populations from the Ganges region were distinct in exhibiting high degrees of both Cd tolerance and hyperaccumulation (one requiring 3 m M Cd for optimal growth), whereas across the other five populations there was an inverse relationship between Cd tolerance and hyperaccumulation, as has been noted previously for Zn. Metal hyperaccumulation was negatively correlated with shoot : root ratio, which could account quantitatively for the differences between populations in shoot Zn (but not Cd) concentrations. On exposure to 30 m m M Cd, the two Ganges populations showed marked reductions in shoot Zn and Fe concentrations, although Cd accumulation was not inhibited by elevated Zn; in the other five populations, 30 m M Cd had little or no effect on Zn or Fe accumulation but markedly reduced shoot Ca concentration. These results support a proposal that Cd is taken up predominantly via a high-affinity uptake system for Fe in the Ganges populations, but via a loweraffinity pathway for Ca in other populations. Total shoot Cd accumulated per plant was much more closely related to population Cd tolerance than Cd hyperaccumulation, indicating that metal tolerance may be the more important selection criterion in developing lines with greatest phytoremediation potential.
290 citations
TL;DR: The overall effect of this invasive shrub is increased mortality of native tree seedlings, suggesting it impacts the natural regeneration of secondary forests.
Abstract: Invasive plants are often associated with reduced cover of native plants, but rarely has competition between invasives and natives been assessed experimentally. The shrub Lonicera maackii, native to northeastern Asia, has invaded forests and old fields in numerous parts of eastern North America, and is associated with reduced tree seedling density in Ohio forests. A field experiment was conducted to test the effects of established L. maackii on the survival and growth of transplanted native tree species. The experiment examined above-ground competition (by removing L. maackii shoots) and below-ground competition (by trenching around transplanted seedlings). The effects of above-ground competition with L. maackii were generally more important than below-ground competition, though both were detected. Shoot treatment was the key determinant for the survival of all species except P. serotina, whereas trenching only enhanced survival for A. saccharum caged and P. serotina, and only in the shoot removal treatment. For the surviving seedlings, L. maackii shoot removal increased growth of A. saccharum seedlings protected with cages, but actually reduced the growth of unprotected Q. rubra and A. saccharum seedlings, indicating that L. maackii shoots confer some protection from deer browsing. Significant interactions between root and shoot treatment on Q. rubra growth parameters, specifically greatest growth in the shoot present & trenched treatment, is attributed to protection from deer browsing combined with release from below-ground competition. Despite this protective function of L. maackii shoots, the overall effect of this invasive shrub is increased mortality of native tree seedlings, suggesting it impacts the natural regeneration of secondary forests.
276 citations
TL;DR: The high responsiveness of many weed species to N may be a weakness to be exploited through development of fertilizer management methods that enhance crop competitiveness with weeds.
Abstract: Information on responses of weeds to various soil fertility levels is required to develop fertilizer management strategies as components of integrated weed management programs. A controlled environment study was conducted to determine shoot and root growth response of 23 agricultural weeds to N fertilizer applied at 0, 40, 80, 120, 180, or 240 mg kg−1 soil. Wheat and canola were included as control species. Shoot and root growth of all weeds increased with added N, but the magnitude of the response varied greatly among weed species. Many weeds exhibited similar or greater responses in shoot and root biomass to increasing amounts of soil N, compared with wheat or canola. With increasing amounts of N, 15 weed species showed a greater increase in shoot biomass, and 8 species showed a greater increase in root biomass, compared with wheat. Ten weed species exhibited increases in shoot biomass similar to that exhibited by canola, and five weed species showed greater increases in root biomass than did c...
272 citations
TL;DR: Application of Si may be one of the available pathways to improve growth of this crop and increase its production in arid or semi arid areas.
Abstract: Plants of wheat growing in pots with silicon (Si) applied before sowing had greater plant height, leaf area, and dry materials compared to those without Si applied in well watering conditions. Drought stress was applied by withholding watering for 12 days from 26‐day old seedlings. In the stress conditions, plants growing in Si‐applied soil could maintain higher relative water content (RWC), water potential and leaf area compared to those without Si applied. Moreover, the Si applied plant dry materials were not significantly changed by drought while those of plants growing in pots without Si applied were significantly decreased, and this was mainly due to growth inhibition of the shoots. Drought stressed wheat growing in pots with Si applied had a significantly greater leaf weight ratio (LWR) and lower specific leaf area (SLA) compared to those of stressed plants in the absence of applied Si. This demonstrates that the leaves of stressed plants growing in pots with Si applied were thicker compare...
268 citations
TL;DR: Na+ accumulation in plants grown in 50 mm NaCl was strongly reduced by increasing Ca2+ activity, and plant survival was improved, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation.
Abstract: Arabidopsis is frequently used as a genetic model in plant salt tolerance studies, however, its physiological responses to salinity remain poorly characterized. This study presents a characterization of initial Na+ entry and the effects of Ca2+ on plant growth and net Na+ accumulation in saline conditions. Unidirectional Na+ influx was measured carefully using very short influx times in roots of 12-d-old seedlings. Influx showed three components with distinct sensitivities to Ca2+, diethylpyrocarbonate, and osmotic pretreatment. Pharmacological agents and known mutants were used to test the contribution of different transport pathways to Na+ uptake. Influx was stimulated by 4-aminobutyric acid and glutamic acid; was inhibited by flufenamate, quinine, and cGMP; and was insensitive to modulators of K+ and Ca2+ channels. Influx did not differ from wild type in akt1 and hkt1 insertional mutants. These data suggested that influx was mediated by several different types of nonselective cation channels. Na+ accumulation in plants grown in 50 mm NaCl was strongly reduced by increasing Ca2+ activity (from 0.05-3.0 mm), and plant survival was improved. However, plant biomass was not affected by shoot Na+ concentration, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation. These data suggest that Arabidopsis is a good model for investigation of Na+ transport, but may be of limited utility as a model for the study of Na+ toxicity.
TL;DR: In this paper, three Bacillus strains, B. subtilis NEB4 and NEB5 and B. thuringiensisNEB17, were isolated from inside the nodules of vigorous field-grown soybean plants in 1998, and were shown to have plant growth promoting activity on pouch-grown beans under greenhouse conditions.
Abstract: Nodulation and subsequent nitrogen fixation by soybean [Glycine max (L.) Merr.] plants are inhibited by low root zone temperatures (RZTs). Plant growth promoting bacteria can help overcome these deleterious effects. Three Bacillus strains, B. subtilis NEB4 and NEB5 and B. thuringiensis NEB17, were isolated from inside the nodules of vigorous field-grown soybean plants in 1998, and were shown to have plant growth promoting activity on pouch-grown soybean plants under greenhouse conditions. To test their ability to improve soybean nodulation and growth under low RZTs, these strains were coinoculated onto soybean plants, with Bradyrhizobium japonicum, under greenhouse conditions at RZTs of 25, 17, and 15°C, and under field conditions in a short growing season area. In all cases, the experiments were conducted with soybean cultivar OAC Bayfield. All the three Bacillus strains enhanced soybean nodulation and growth in greenhouse and field experiments. Coinoculation with NEB17 provided the largest and most consistent increases in nodule number, nodule weight, shoot weight, root weight, total biomass, total nitrogen, and grain yield. The other two strains provided positive responses in only 1 of the 2 yr of field-testing. Thus, B. thuringiensis NEB17 would be suitable for use as a plant growth promoting bacterial strain in soybean production systems in short growing season regions.
TL;DR: It is deduced that CAT and APX are most important for cold acclimation and chilling tolerance, and increased activity of antioxidants in roots is more important forcold tolerance than increased activity in shoots.
Abstract: Rice (Oryza saliva L.) is a tropical crop, but is also grown in temperate regions in late spring to summer. Cold temperature damage is a common problem for early-planted rice in temperate countries. Physiological responses to chilling, including antioxidative enzyme activity, were investigated in rice to identify mechanisms of chilling tolerance. Plants were exposed to 15°C (cold-acclimated) or 25°C (nonacclimated) for 3 d, under 250 μmol m -2 s -1 photosynthetically active radiation (PAR). All plants were then exposed to chilling temperature at 5°C for 3 d and allowed to recover at 25°C for 5 d. Leaf fresh weight, relative water content, lipid peroxidation, chlorophyll a fluorescence, and quantum yield showed that cold-acclimated leaves were less affected by chilling compared to nonacclimated leaves. Cold-acclimated leaves also recovered faster from chilling injury than nonacclimated leaves. We analyzed the isozyme profile and activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Significant induction of expression and activity of antioxidative enzymes CAT and APX in leaves and SOD, CAT, APX, and GR in roots were observed. We deduced that CAT and APX are most important for cold acclimation and chilling tolerance. Increased activity of antioxidants in roots is more important for cold tolerance than increased activity in shoots. Chilling-sensitive rice plants can be made tolerant by cold acclimation.
TL;DR: Two models for root : shoot allocation were investigated, with and without explicit inclusion of maintenance respiration, and the model without respiration gave qualitatively reasonable results when predictions were compared with observed results from growth experiments with birch and tomato.
TL;DR: In this paper, the stable carbon isotope composition (d 13 C) of leaves and current-year stems were examined in beech trees over one year and the dynamics of the d d d 13 C and content of nonstructural sugars were also assessed.
Abstract: Temporal variations in the stable carbon isotope composition (d 13 C) of leaves and current-year stems were examined in beech trees over one year. The d 13 C of both tissues were equal in the bud stage and started to diverge during growth, with values decreasing by 2·5 and 4·5‰ for stems and leaves, respectively. The dynamics of the d d d 13 C and content of non-structural sugars were also assessed. The beginning of the growth period was characterized by a decrease in starch content and high starch d 13 C values. Later in the season, the d 13 C of leaf soluble sugars progressively decreased from the end of May and the d d d 13 C of stem sucrose was at least 1·5‰ higher than that of leaves. The d 13 C of CO 2 respired by stem tissue increased during stem growth and exhibited large seasonal variations (from - 22·1 to - - 26·3‰). These values generally fell between those of starch and total organic matter. The results of the study showed that the d 13 C of stems is altered by two apparent fractionation steps: one during sugar transfer from leaves to stems and one during stem respiration. These results may have implications for analysis of isotopic signals in tree rings and forest ecosystems.
TL;DR: The terminating floral meristem incorporates the spatial regulation scheme into a temporal regulation pathway involving flower patterning factors, and regulates stem tissues and lateral organs throughout the life of a plant.
TL;DR: It is concluded that the effect of mycorrhizal colonisation on the bacterial community structure in the rhizosphere may, at least in part, be plant-mediated.
Abstract: Maize plants were grown in an autoclaved quartz sand–soil mix to which the bacterial communities of the soil and the mycorrhizal inocula were reintroduced. The root systems of the plants were divided with the two halves growing in separate pots. There were five different treatments: plants with both root halves non-mycorrhizal either at high or low P availability (nm-nm HP and nm-nm LP) or mycorrhizal plants grown at low P availability with one side of the root system non-mycorrhizal while the other side was inoculated with Glomus intraradices (GI-nm) or G. mosseae (GM-nm) or plants with both sides mycorrhizal but each side inoculated with a different fungus (GI–GM). The plants were harvested after 3 or 6 weeks. Shoot dry weight and shoot P concentration of the nm-nm HP plants were always higher than the plants grown at low P supply. Acid phosphatase activity in the rhizosphere was similar in all treatments and did not change over time. However, after 6 weeks alkaline phosphatase activity was higher in the rhizosphere of both root halves in the mycorrhizal plants as compared to the non-mycorrhizal plants. Mycorrhizal colonisation increased from 15–34% after 3 weeks to 78–87% after 6 weeks with no significant difference between GI and GM. The bacterial community structure, assessed by denaturing gradient gel electrophoresis (DGGE), changed over time and was specific for each of the three compartments, non-rhizosphere soil, rhizosphere soil and root surface. While the two P levels in the non-mycorrhizal treatments had no significant effect on the bacterial communities, mycorrhizal colonisation changed the bacterial community structure on the root surface and in the non-rhizosphere soil. The bacterial communities of the GI–GM plants differed more from the non-mycorrhizal plants than those of the plants with only one half of the root system mycorrhizal. The bacterial communities of both root halves of the GI-nm plants did not differ from each other and were very similar to those of the non-mycorrhizal plants. After 3 weeks, the bacterial communities of the two sides of the GM-nm plants differed: the mycorrhizal side of the resembled that of the GI–GM plants, while the non-mycorrhizal side of the root system was similar to that of the nm-nm plants. However after 6 weeks, the bacterial community structures of the two sides of the root system of the GM-nm plants were similar and differed from those of the nm-nm plants. It is concluded that the effect of mycorrhizal colonisation on the bacterial community structure in the rhizosphere may, at least in part, be plant-mediated.
TL;DR: Black mustard contains water-soluble substances that inhibited the germination and seedling growth of wild oat and this study investigated the allelopathic effects of various B. nigra plant parts on A. fatua L. germination, seedling length and weight.
TL;DR: In this paper, two wheat varieties were grown in a controlled environment with cadmium near threshold concentrations supplying the metal at equal-effect concentrations, i.e., at the lowest metal concentration and the activation in roots of the antioxidative enzymes catalase, ascorbate peroxidase and guaiacol peroxidease.
TL;DR: This is the first report of plant growth-promoting bacilli with the ability to catabolize ACC, and a soil inoculation with B. globisporus DUC3 promoted root and shoot growth of plants subjected to a diurnal temperature regime.
TL;DR: The results indicate that the tolerance level of indica was higher than that of japonica, and reduction in all growth parameters of tolerant varieties was significantly lower in indica varieties than inJaponica varieties.
Abstract: In order to identify the degree of salinity tolerance of the indica and japonica rice groups, 10 varieties were tested under saline and non-saline conditions. Twelve-day-old seedlings were grown in normal culture solution, then initially salinized at an electrical conductivity (EC) of 6 dS/m for 4 days, and finally salinized at an EC of 12 dS/m for the next 14 days. The growth parameters, and Na and K absorption in the shoot were measured to characterize the tolerance level of the two rice groups. Reduction in all growth parameters of tolerant varieties was significantly lower in indica varieties than in japonica varieties. Tolerant indica varieties were good Na excluders, absorbed high amounts of K, and maintained a low Na/K ratio in the shoot. Tolerant japonica varieties also absorbed less Na but were not as good excluders as indica varieties. Shoot K concentration alone did not show any relationship to salinity tolerance. These results indicate that, for all parameters measured, the tolerance level of indica was higher than that of japonica.
TL;DR: The first report of the mitigation of the adverse effect of water stress on yield and quality of a fruit crop was reported, with significantly higher biomass and fruit yield compared to nonmycorrhizal plants, whether plants were water stressed or not.
Abstract: The effect of arbuscular mycorrhizal (AM) colonisation by Glomus clarum on fruit yield and water use efficiency (WUE) was evaluated in watermelon (Citrullus lanatus) cv. Crimson Sweet F1 under field conditions. Treatments were: (1) well-watered plants without mycorrhizae (WW-M), (2) well-watered plants with mycorrhizae (WW+M), (3) water- stressed plants without mycorrhizae (WS-M) and (4) water-stressed plants with mycorrhizae (WS+M). When soil water tension readings reached −20 and −50 kPa for well-watered (WW) and water-stressed (WS) treatments, respectively, irrigation was initiated to restore the top soil to near field capacity. Water stress reduced watermelon shoot and root dry matter, fruit yield, water use efficiency but not total soluble solids (TSS) in the fruit, compared with the non-stressed treatments. Mycorrhizal plants had significantly higher biomass and fruit yield compared to nonmycorrhizal plants, whether plants were water stressed or not. AM colonisation increased WUE in both WW and WS plants. Macro- (N, P, K, Ca and Mg) and micro- (Zn, Fe and Mn) nutrient concentrations in the leaves were significantly reduced by water stress. Mycorrhizal colonisation of WS plants restored leaf nutrient concentrations to levels in WW plants in most cases. This is the first report of the mitigation of the adverse effect of water stress on yield and quality of a fruit crop.
TL;DR: Normal levels of endogenous ABA maintain shoot development, particularly leaf expansion, in well-watered Arabidopsis plants, partly by suppressing ethylene synthesis and partly by another mechanism that is independent of ethylene.
Abstract: Previous work demonstrated that normal levels of endogenous abscisic acid (ABA) are required to maintain shoot growth in well-watered tomato plants independently of effects of hormone status on plant water balance. The results suggested that the impairment of shoot growth in ABA-deficient mutants is at least partly attributable to increased ethylene production. To assess the extent to which ABA maintains shoot growth by ethylene suppression, the growth of ABA-deficient (aba2-1) and ethylene-insensitive (etr1-1) single- and double-mutants of Arabidopsis was examined. To ensure that the results were independent of effects of hormone status on plant water balance, differential relative humidity regimes were used to achieve similar leaf water potentials in all genotypes and treatments. In aba2-1, shoot growth was substantially inhibited and ethylene evolution was doubled compared with the wild type, consistent with the results for tomato. In the aba2-1 etr1-1 double mutant, in which ABA was equally as deficient as in aba2-1 and shoot growth was shown to be insensitive to ethylene, shoot growth was substantially, although incompletely, restored relative to etr1-1. Treatment with ABA resulted in the complete recovery of shoot growth in aba2-1 relative to the wild type, and also significantly increased the growth of aba2-1 etr1-1 such that total leaf area and shoot fresh weight were not significantly lower than in etr1-1. In addition, ABA treatment of aba2-1 etr1-1 restored the wider leaf morphology phenotype exhibited by etr1-1. The results demonstrate that normal levels of endogenous ABA maintain shoot development, particularly leaf expansion, in well-watered Arabidopsis plants, partly by suppressing ethylene synthesis and partly by another mechanism that is independent of ethylene.
TL;DR: Results indicated that over-expression of HvPIP2;1 makes rice plants sensitive to 100 mM NaCl, and the possible involvement of aquaporins in salt tolerance is discussed.
Abstract: Barley HvPIP2;1 is a plasma membrane aquaporin and its expression was down-regulated after salt stress in barley [Katsuhara et al. (2002) Plant Cell Physiol. 43: 885]. We produced and analyzed transgenic rice plants over-expressing barley HvPIP2;1 in the present study. Over-expression of HvPIP2;1 increased (1) radial hydraulic conductivity of roots (Lp(r)) to 140%, and (2) the mass ratio of shoot to root up to 150%. In these transgenic rice plants under salt stress of 100 mM NaCl, growth reduction was greater than in non-transgenic plants. A decrease in shoot water content (from 79% to 61%) and reduction of root mass or shoot mass (both less than 40% of non-stressed plants) were observed in transgenic plants under salt stress for 2 weeks. These results indicated that over-expression of HvPIP2;1 makes rice plants sensitive to 100 mM NaCl. The possible involvement of aquaporins in salt tolerance is discussed.
TL;DR: Different light and nutrient availability enhanced the growth of P. amplifolius and Nuphar advena and caused differences in leaf traits, which did not result in detectable differences in damage by herbivores.
Abstract: Phenotypic responses of Potamogeton amplifolius and Nuphar advena to different light (7% and 35% of surface irradiance) and nutrient environments were assessed with field manipulation experiments. Higher light and nutrient availability enhanced the growth of P. amplifolius by 154% and 255%, respectively. Additionally, biomass was allocated differently depending on the resource: high light availability resulted in a higher root/shoot ratio, whereas high nutrient availability resulted in a lower root/shoot ratio. Low light availability and high nutrient availability increased the nitrogen content of leaf tissue by 53% and 40% respectively, resulting in a 37% and 31% decrease in the C/N ratio. Root nitrogen content was also increased by low light and high nutrient availability, by 50% (P=0.0807) and 77% respectively, resulting in a 20% and 40% decrease in root C/N ratio. Leaf phenolics were significantly increased 72% by high light and 31% by high nutrient availability, but root phenolic concentrations were not altered significantly. None of these changes in tissue constituents resulted in altered palatability to crayfish. N. advena was killed by the same high nutrient treatment that stimulated growth in P. amplifolius, preventing assessment of phenotypic responses to nutrient availability. However, high light availability increased overall growth by 24%, but this was mainly due to increased growth of the rhizome (increased 100%), resulting in a higher root/shoot ratio. High light tended to increase the production of floating leaves (P=0.09) and significantly decreased the production of submersed leaves. High light availability decreased the nitrogen content by 15% and 25% and increased the phenolic concentration by 88% and 255% in floating and submersed leaves, respectively. These differences in leaf traits did not result in detectable differences in damage by herbivores.
TL;DR: The bacteria isolates were able to survive in the rhizosphere and in the soil of winter wheat after root and shoot inoculation and resulted in significantly higher N, P, and K contents of plant components.
Abstract: Plant-growth-promoting bacteria isolated from the rhizosphere, phyllosphere and soil of the root zone in different climatic regions of Germany and Uzbekistan were analysed for plant-growth-promoting effects and nutrient uptake on winter wheat on different soils and under different temperature regimes. The investigations were carried out in pot experiments using loamy sand and sandy loam soils from Muncheberg, Germany and Calcisol soil from Tashkent, Uzbekistan. The temperature and soil types were found to influence growth-promoting effects. Inoculation with bacterial strains Pseudomonas fluorescens PsIA12, Pantoea agglomerans 050309 and Mycobacterium sp. 44 isolated from Muncheberg (semi-continental climate) was found to significantly increase the root and shoot growth of winter wheat at 16 °C compared to 26 °C in loamy sand. Mycobacterium phlei MbP18 and Mycoplana bullata MpB46 isolated from Tashkent (semi-arid climate) were found to significantly increase the root and shoot growth of winter wheat in nutrient-poor Calcisol at 38 °C as well as in nutrient-rich loamy sand at 16 °C. Bacterial inoculation also resulted in significantly higher N, P, and K contents of plant components. The bacteria isolates were able to survive in the rhizosphere and in the soil of winter wheat after root and shoot inoculation.
TL;DR: The reduced ascorbate was thus able to replenish reducing equivalents to phenoxyl radicals thus explaining the increase in the phenolic compounds.
Abstract: Raphanus sativus L. cv. Rimbo was grown for 10 days after emergence in hydroponic culture containing 0.12 (control), 5, 10 and 15 micro M copper. The seeds were germinated in the presence of the copper solution. The Cu contents increased with the treatment in both shoots and roots, maintaining in the roots a value eight- to ten-fold higher than in the shoots. With the treatment both shoots and roots underwent growth inhibition and an increase in the percentage of dry weight. Membrane damage and lipid peroxidation increased and glutathione was oxidized as the copper concentration increased, indicating an acceleration of oxidative processes. Control shoots had high contents of reduced glutathione and low contents of phytochelatin-SH whereas roots showed an opposite pattern, suggesting an utilization of reduced glutathione for phytochelatin synthesis. In both parts phytochelatin-SH content reached the maximum at 5 micro M copper and then decreased, reaching at 15 micro M copper the control value in the roots and a value five-fold higher than the control value in the shoots. The main phenolic acids represented in R. sativus were chlorogenic, vanillic, caffeic, siringic, p-coumaric and ferulic acids whereas the least represented were gallic, protocatechuic and p-hydroxybenzoic acids. The phenolic acids as well as the total and reduced ascorbate contents increased with the intensification of copper treatment. Notwithstanding these changes, total ascorbate remained 35% higher in the shoots than in the roots. The reduced ascorbate was thus able to replenish reducing equivalents to phenoxyl radicals thus explaining the increase in the phenolic compounds.
01 Jan 2003
TL;DR: The advantages of grafting plants for current agriculture are examined, these being: resistance to evermore frequent soil diseases; tolerance of low temperatures characteristic of many latitudes of the world where intensive cultivation is economically important; tolerance to the growing problem of salinity from abuse of chemical fertilizers and desertification in many agricultural zones; and enhanced water and inorganic-nutrient uptake.
Abstract: The cultivation of grafted plants have gradually increased in the last years. As the use of this technique spread, the aims also expanded until today when grafting serves a spectrum of purposes: (1) to boost plant growth and development; (2) to control wilt caused by pathogens; (3) to reduce viral, fungal and bacterial infection; (4) to strengthen tolerance to thermal or saline stress; (5) to increase nutrient and mineral uptake to the shoot, etc. Throughout this review, we have examined the advantages of grafting plants for current agriculture, these being: resistance to evermore frequent soil diseases; tolerance of low temperatures characteristic of many latitudes of the world where intensive cultivation is economically important; tolerance to the growing problem of salinity from abuse of chemical fertilizers and desertification in many agricultural zones; and enhanced water and inorganic-nutrient uptake. All these advantages provide motivation for grafting in present-day world agriculture.
TL;DR: In this article, the first long-term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years).
Abstract: . Use of high biomass crops such as the willow Salix viminalis to extract metals for soil remediation has been proposed as an alternative to the low biomass-producing hyperaccumulating plants. High yields compensate for the moderate heavy-metal concentrations in the shoots of such species. We report the first long-term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years). Total metals extracted by the plants were 170 g Cd ha−1 and 13.4 kg Zn ha−1 from the calcareous soil after 5 years, and 47 g Cd ha−1 and 14.5 kg Zn ha−1 from the acidic soil after 2 years; in the first year outputs were negligible. After 2 years, Salix had performed better on the acidic soil because of larger biomass production and higher metal concentrations in shoots. Addition of elemental sulphur to the soil did not yield any additional benefit in the long term, but application of an Fe chelate improved the biomass production. Cd and Zn concentrations were significantly higher in leaves than stems, highlighting the necessity to collect leaves as well as shoots. On both soils, concentration in shoots decreased with time, indicating a decrease in extraction efficiency.
TL;DR: Although the experimental plants faced major herbivore-induced growth changes, plant reproduction was similar in all treatments, documenting their ability to effectively compensate for leaf and root herbivory.
Abstract: Separate and combined effects of root and leaf herbivores on plant growth, flower visitation and seed set were tested in a factorial experiment using potted mustard, Sinapis arvensis, at an old fallow field. A 50% leaf removal by cabbageworms (Pieris rapae) when the seedlings had their first four leaves reduced plant height and shoot mass, and delayed the onset of flowering. Root herbivory by two wireworms (Agriotes sp.) over the whole experiment changed flower visitation; the number of flower visitors per plant was higher in plants with root herbivores than in plants without root herbivores. Combined leaf and root herbivory affected flowering period, number of fruits per plant and number of seeds per fruit. Plants attacked by leaf and root herbivores had a shorter flowering period and produced fewer fruits per plant than plants with root herbivores only. Although the experimental plants faced major herbivore-induced growth changes, plant reproduction (seed set and weight per plant) was similar in all treatments, documenting their ability to effectively compensate for leaf and root herbivory.