Effect of seed phosphorus concentration on nodulation and growth of three common bean cultivars

Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH₂PO₄ solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg^?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N₂ fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.     

Biochar as a strategy to manage plant diseases caused by pathogens inhabiting the soil: a critical review

Phytoparasitica - The current agricultural scenario faces a range of challenges, with phytosanitary ones being paramount. In most cases, plant diseases are treated with chemicals; however, they...     

Zinc phosphate protects tomato plants against Pseudomonas syringae pv. tomato

Journal of Plant Diseases and Protection - The purpose of this study was to determine whether zinc phosphate treatments of tomato plants (Solanum lycopersicum L.) can attenuate bacterial speck...     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

Temporal dynamics of stem expansion and contraction in savanna trees: withdrawal and recharge of stored water

Relationships between diel changes in stem expansion and contraction and discharge and refilling of stem water storage tissues were studied in six dominant Neotropical savanna (cerrado) tree species from central Brazil. Two stem tissues were studied, the active xylem or sapwood and the living tissues located between the cambium and the cork, made up predominantly of parenchyma cells (outer parenchyma). Outer parenchyma and sapwood density ranged from 320 to 410 kg m(-3) and from 420 to 620 kg m(-3), respectively, depending on the species. The denser sapwood tissues exhibited smaller relative changes in cross-sectional area per unit change in water potential compared with the outer parenchyma. Despite undergoing smaller relative changes in cross-sectional area, the sapwood released about 3.5 times as much stored water for a given change in area as the outer parenchyma. Cross-sectional area decreased earlier in the morning in the outer parenchyma than in the sapwood with lag times up to 30 min for most species. The relatively small lag time between dimensional changes of the two tissues suggested that they were hydraulically well connected. The initial morning increase in basal sap flow lagged about 10 to 130 min behind that of branch sap flow. Species-specific lag times between morning declines in branch and main stem cross-sectional area were a function of relative stem water storage capacity, which ranged from 16 to 31% of total diurnal water loss. Reliance on stored water to temporarily replace transpirational losses is one of the homeostatic mechanisms that constrain the magnitude of leaf water deficits in cerrado trees.     

Variability of trace metal concentrations in Jeffrey pine (Pinus jeffreyi) tree rings from the Tahoe Basin, California, USA

Trace metal accumulation in tree rings of Jeffrey pines (Pinus jeffreyi) from the Lake Tahoe basin (Sierra Nevada, CA, USA) was determined using high resolution inductively coupled plasma mass spectrometry (HR-ICP–MS). The objectives of this study were (1) to establish baseline values for aluminium (Al), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), strontium (Sr), cadmium (Cd), barium (Ba), and lead (Pb); (2) to investigate the intra-tree and inter-tree variability of these trace metals, and (3) to assess differences in metal concentrations related to automobile traffic. Two field collection sites were selected with similar ecologic attributes, one proximal to a heavily traveled highway, and the other isolated from any local source of auto emissions. At each site two trees with similar features were selected, and two increment cores collected from each tree. Cores were cross-dated, cleaned of contamination, dissected into 5-year increments, ashed, and acid digested, before analysis by HR-ICP–MS. Time series spanning 191–326 years were developed for the 12 trace metals. Variability was high within and between trees, most likely because of physiologic mechanisms for element sequestration and allocation. The best intra-tree correlation was found for Ba, Sr, Mn, and Co; of these elements, Co showed an overall increase over time, whereas Sr and Ba displayed an opposite trend, and Mn fluctuated over time. Mean Co concentration at the near-highway site was higher, whereas mean Sr, Ba, and Mn concentrations were lower, than at the control site.     

Removal of nutrient limitations by long-term fertilization decreases nocturnal water loss in savanna trees

Under certain environmental conditions, nocturnal transpiration can be relatively high in temperate and tropical woody species. We have previously shown that nocturnal sap flow accounts for up to 28% of total daily transpiration in woody species growing in a nutrient-poor Brazilian Cerrado ecosystem. In the present study, we assessed the effect of increased nutrient supply on nocturnal transpiration in three dominant Cerrado tree species to explore the hypothesis that, in nutrient-poor systems, continued transpiration at night may enhance delivery of nutrients to root-absorbing surfaces. We compared nocturnal transpiration of trees growing in unfertilized plots and plots to which nitrogen (N) and phosphorus (P) had been added twice yearly from 1998 to 2005. Three independent indicators of nocturnal transpiration were evaluated: sap flow in terminal branches, stomatal conductance (g(s)), and disequilibrium in water potential between covered and exposed leaves (DeltaPsi(L)). In the unfertilized trees, about 25% of the total daily sap flow occurred at night. Nocturnal sap flow was consistently lower in the N- and P-fertilized trees, significantly so in trees in the N treatment. Similarly, nocturnal g(s) was consistently lower in fertilized trees than in unfertilized trees where it sometimes reached values of 150 mmol m(-2) s(-1) by the end of the dark period. Predawn gs and the percentage of nocturnal sap flow were linearly related. Nocturnal DeltaPsi(L) was significantly greater in the unfertilized trees than in N- and P-fertilized trees. The absolute magnitude of DeltaPsi(L) increased linearly with the percentage of nocturnal sap flow. These results are consistent with the idea that enhancing nutrient uptake by allowing additional transpiration to occur at night when evaporative demand is lower may avoid excessive dehydration associated with increased stomatal opening during the day when evaporative demand is high.     

Drying and wetting of Mediterranean soils stimulates decomposition and carbon dioxide emission: the "Birch effect"

Observations on the net carbon exchange of forests in the European Mediterranean region, measured recently by the eddy covariance method, have revived interest in a phenomenon first characterized on agricultural and forest soils in East Africa in the 1950s and 1960s by H. F. Birch and now often referred to as the "Birch effect." When soils become dry during summer because of lack of rain, as is common in regions with Mediterranean climate, or are dried in the laboratory in controlled conditions, and are then rewetted by precipitation or irrigation, there is a burst of decomposition, mineralization and release of inorganic nitrogen and CO(2). In forests in Mediterranean climates in southern Europe, this effect has been observed with eddy covariance techniques and soil respiration chambers at the stand and small plot scales, respectively. Following the early work of Birch, laboratory incubations of soils at controlled temperatures and water contents have been used to characterize CO(2) release following the rewetting of dry soils. A simple empirical model based on laboratory incubations demonstrates that the amount of carbon mineralized over one year can be predicted from soil temperature and precipitation regime, provided that carbon lost as CO(2) is taken into account. We show that the amount of carbon returned to the atmosphere following soil rewetting can reduce significantly the annual net carbon gain by Mediterranean forests.