Relationship of endogenous abscisic Acid to sucrose level and seed growth rate of soybeans

It has been proposed that abscisic acid (ABA) may stimulate sucrose transport into filling seeds of legumes, potentially regulating seed growth rate. The objective of this study was to determine whether the rate of dry matter accumulation in seeds of soybeans (Glycine max L.) is correlated with the endogenous levels of ABA and sucrose in those sinks. The levels of ABA and sucrose in seed tissues were compared in nine diverse Plant Introduction lines having seed growth rates ranging from 2.5 to 10.0 milligrams dry weight per seed per day. At 14 days after anthesis (DAA), seeds of all genotypes contained less than 2 micrograms of ABA per gram fresh weight. Levels of ABA increased rapidly, however, reaching maxima at 20 to 30 DAA, depending upon tissue type and genotype. ABA accumulated first in seed coats and then in embryos, and ABA maxima were higher in seed coats (8 to 20 micrograms per gram fresh weight) than in embryos (4 to 9 micrograms per gram fresh weight. From 30 to 50 DAA, ABA levels in both tissues decreased to less than 2 micrograms per gram fresh weight. Levels of sucrose were also low early in development, less than 10 milligrams per gram fresh weight at 14 DAA. However, by 30 DAA, sucrose levels in seed coats had increased to 20 milligrams per gram fresh weight and remained fairly constant for the remainder of the filling period. In contrast, sucrose accumulated in embryos throughout the filling period, reaching levels greater than 40 milligrams per gram fresh weight by 50 DAA. Correlation analyses indicated that the level of ABA in seed coats and embryos was not directly correlated to the level of sucrose measured in those tissues or to the rate of seed dry matter accumulation during the linear filling period. Rather, the ubiquitous pattern of ABA accumulation early in development appeared to coincide with water uptake and the rapid expansion of cotyledons occurring at that time. Whole tissue sucrose levels in embryos and seed coats, as well as sucrose levels in the embryo apoplast, were generally not correlated with the rate of dry matter accumulation. Thus, it appears that, in this set of diverse soybean genotypes, seed growth rate was not limited by endogenous concentrations of ABA or sucrose in reproductive tissues.     

Comparative metabolic clearance rates of beta-endorphin and beta-lipotropin in humans

In normal human subjects under basal conditions, we have reported that molar concentrations of immunoreactive β-lipotropin (IR-β-LPH) are approximately threefold greater than those of IR-β-endorphin (β-Ep). Following acute stimulation, there is a further two- to threefold disproportionate rise in plasma concentrations of IR-β-LPH as compared to those of IR-β-Ep. To begin to assess the possible factors involved in such altered IR-β-LPH/IR-β-Ep ratios in plasma, the metabolic clearance rate (MCR), volume of distribution (V_d), fractional rate of disappearance (K_d), and half-life ($\text{t}\text{1}\text{2}$) of these peptides were determined by means of bolus injection of highly purified human β-LPH and synthetic human β-Ep in normal human subjects. β-Ep was found to have an MCR and a K_d greater than that of β-LPH, and a shorter $\text{t}\text{1}\text{2}$. These differences, however, although they may in part be contributory, cannot solely account for the greater ratio of IR-β-LPH to IR-β-Ep in plasma, or for the disproportionate rise in plasma concentrations of these peptides after acute stimulation.     

Effect of Water Deficits on Seed Development in Soybean : II. Conservation of Seed Growth Rate

Water deficits during seed filling decrease seed size in soybean (Glycine max L.). This may result from a reduction in the supply of assimilates from the maternal plant and/or an inhibition of seed metabolism. To determine whether maternal or zygotic factors limited seed growth, we examined the effects of a plant water deficit on the supply of sucrose to and its utilization by developing embryos. Plants were grown in the greenhouse, and water deficits were imposed by withholding water for a period of 6 days during linear seed fill. When water was withheld, leaf water potential decreased rapidly, inhibiting canopy photosynthesis completely within 3 days. However, seed dry weight (nodes 7-11) continued to increase at or near the control rate. The level of total extractable carbohydrates in leaf, stem, and pericarp tissue decreased by 70, 50, and 45%, respectively, indicating that reserves were mobilized to support seed growth. Cotyledon sucrose content decreased from about 60 milligrams per gram dry weight to 30 milligrams per gram dry weight. Similarly, the concentration of sucrose in the interfacial apoplast of the cotyledons decreased from approximately 100 millimolar to 50 millimolar. However, the rate of sucrose accumulation by excised embryos, measured in a short-term in vitro assay, increased in response to the water deficit. These results indicate that both source and sink activity in soybean are altered by water deficits to maintain the flux of assimilates to the developing embryos. This may explain why seed growth is maintained, albeit for a shorter duration, when soybean is exposed to water deficits during the seed filling period.     

Changes in cell structure during the formation of root aerenchyma inSAGITTARIA LANCIFOLIA (Alismataceae)

In many wetland species, root aerenchyma is produced by the predictable collapse of root cortex cells, indicating a programmed cell death (PCD). The objective of this study was to characterize the cellular changes that accompany this PCD in the marsh species Sagittaria lancifolia. Structural changes in membranes and organelles were examined during development of root cortex cells to compare with previous examples of PCD. The organization of cortical microtubule (CMT) arrays in root cells from S. lancifolia was also evaluated as a possible predictor of cell lysis. Nuclear fragmentation and condensation were the earliest changes observed in cells undergoing lysis. Breakdown of the tonoplast and other organelles and disruption of the plasma membrane followed. After loss of cytoplasm, cells collapsed to form gas spaces. These results were compared to collapse of root cortical cells of Zea mays and Oryza sativa during aerenchyma development. Changes in the appearance of the cytoplasm of all three species were similar at later stages of aerenchyma development. The relative timing of disintegration of the tonoplast and middle lamella appeared to differ among the three species. Changes in the organization of CMT arrays did not appear to be a predictor of PCD in S. lancifolia. Aerenchyma production in plants involves a type of PCD that is morphologically distinct from PCD described from many animals.     

Detoxification of ochratoxin A,a food contaminant: Prevention of growth of Aspergillus ochraceus and its production of ochratoxin A

The toxicity of ochratoxin A (OTA), a mycotoxin produced by fungi ofAspergillus orPenicillium genera is now well documented. Its nephrotoxicity, immunosuppression, teratogenicity, and carcinogenicity have been widely studied. Physical and biochemical methods have been studied to prevent these toxinogenicAspergillus andPenicillium from producing OTA, and/or to destroy the mycotoxin when already produced in a liquid or a solid medium. Repeated freezing at ? 20?C and thawing at + 26?C aleatory reduce OTA production in a liquid medium. Exposure to UV B for different periods of time is efficient in preventing OTA production in a liquid medium. Gamma-irradiation from 2 to 5 kGy gives good results in preventing the production of OTA or destroying it when already produced. Carboxypeptidase is very efficient at 5 units/50 ml in a liquid medium for cleaving the OTA already produced.     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

A New Species of Scutellospora with a Coiled Germination Shield

During a survey of mycorrhizal fungi on the upper part of theCisadane River, on the slopes of Mount Pangrango in Gede PangrangoNational Park, West Java, an undescribed species of Scutellospora(Glomales)was discovered. This species has metallic golden to yellow toyellowish-brown spores that possess columnar protuberances.It is described and named Scutellospora projecturata sp. nov.The sequence of the nearly complete SSU rRNA gene was analysedand phylogenetic trees constructed. Copyright 2000 Annals ofBotany Company Scutellospora projecturata, Glomales, new species, 18s SSU rRNA, West Java, phylogenetic tree, phylogeny, arbuscular mycorrhizal fungi, AMF     

Nuclear gene trees and the phylogenetic relationships of the mangabeys (Primates: Papionini)

Phylogenetic relationships of mangabeys within the Old World monkey tribe Papionini are inferred from analyses of nuclear DNA sequences from five unlinked loci. The following conclusions are strongly supported, based on congruence among trees derived for the five separate gene regions: (1) mangabeys are polyphyletic within the Papionini; (2) Cercocebus is the sister taxon to the genus Mandrillus; and (3) Lophocebus belongs to a clade with Papio and Theropithecus, with Papio as its most likely sister taxon. Morphologically based phylogenies positing mangabey monophyly were evaluated by mapping the sequences for each locus on these trees. The data seem to fit these trees poorly in both maximum-parsimony and likelihood analyses. Incongruence among nuclear gene trees occurred in the interrelationships among Lophocebus, Papio, and Theropithecus. Several factors that may account for this incongruence are discussed, including sampling error, random lineage sorting, and introgression.      

Low Water Potential Disrupts Carbohydrate Metabolism in Maize (Zea mays L.) Ovaries

Water deficit during pollination increases the frequency of kernel abortion in maize (Zea mays L.). Much of the kernel loss is attributable to lack of current photosynthate, but a large number of kernels fail to develop on water-deficient plants even when assimilate supply is increased. We examined the possibility that assimilate utilization by developing ovaries might be impaired at low water potential ([Psi]w). Plants were grown in the greenhouse in 20-L pots containing 22 kg of amended soil. Water was withheld on the first day silks emerged, and plants were hand-pollinated 4 d later when leaf [Psi]w decreased to approximately - 1.8 MPa and silk [Psi]w was approximately -1.0 MPa. Plants were rehydrated 2 d after pollination. The brief water deficit inhibited ovary growth (dry matter accumulation) and decreased kernel number per ear by 60%, compared to controls. Inhibition of ovary growth was associated with a decrease in the level of reducing sugars, depletion of starch, a 75-fold increase in sucrose concentration (dry weight basis), and inhibition of acid invertase (EC 3.2.1.26) activity. These results indicate that water deficits during pollination disrupt carbohydrate metabolism in maize ovaries. They suggest that acid invertase activity is important for establishing and maintaining reproductive sink strength during pollination and early kernel development.