Phosphorus threshold for arbuscular mycorrhizal colonization of crops and tree seedlings

The study was conducted to investigate the effect of phosphorus (P) concentrations (0, 5, 10, 20, 50, and 100 μg g⁻¹) on growth and arbuscular mycorrhizal (AM) colonization of two crops (a rainy season crop, Phaseolus mungo Roxb. var. PU-35 and a winter crop, Triticum aestivum L. var. WH-147) and seedlings of two multipurpose tree species (Eucalyptus tereticornis Sm. [Clone C-7, ITC, Bhadrachalam] and Albizia procera Benth.). Plant growth parameters (shoot length, dry weight) and P uptake increased significantly after inoculations with AM fungi (Acaulospora scrobiculata Trappe, Glomus cerebriforme McGee, and Glomus intraradices Schenck and Smith) in P. mungo, T. aestivum, E. tereticornis, and A. procera. Best results were obtained with G. cerebriforme in P. mungo and A. procera, and A. scrobiculata in T. aestivum, and G. intraradices in E. tereticornis. Results on effect of P application on mycorrhizal dependency (MD) of studied crop and tree species showed that decrease in MD with increase in P concentrations in non-nitrogen-fixing species (T. aestivum and E. tereticornis) was higher than in nitrogen-fixing species (P. mungo and A. procera). Threshold P concentrations for maximum benefits from the AM symbiosis in above-mentioned plant species varied from 5 to 20 μg g⁻¹ and corresponding peaks of arbuscules, vesicles, sporocarp formation, colonization index, and spore count per 100 g sand were noticed. Thus, the results showed that the recorded plant growth peaks were due to AM colonization of crops and tree rhizosphere. Inoculations with AMF were more important than P application (explaining 14–78% variation in plant growth) for P. mungo, T. aestivum, and A. procera (forward selection method), whereas P application was more important for growth in E. tereticornis. Therefore, inoculating plants with a suitable AM inoculant could result in a benefit comparable to high P input and lead to a significant saving of inorganic P fertilizer.     

Methyl donors potentiates growth, metabolic status and neurotransmitter enzyme in Labeo rohita fingerlings exposed to endosulfan and temperature

A 2-month preliminary study was conducted to delineate the effect of dietary methyl donors (choline, betaine, and lecithin) on the growth performance and metabolic status of Labeo rohita fingerlings subjected to endosulfan alone and in combination with elevated temperature. Four iso-caloric and iso-nitrogenous diets viz. basal diet, betaine-supplemented diet, choline-supplemented diet and lecithin-supplemented diet were prepared and fed to the different experimental groups throughout the experimental period as per the design. Two hundred and seventy fingerlings (average weight 7.95?±?0.04?g) were randomly distributed in six treatment groups each having three replicates. The experimental groups were as follows: fish subjected to normal water (without endosulfan) and fed with control diet (control group T(0)), fish subjected to endosulfan-treated water and fed with control diet (T(1)), fish subjected to concurrent exposure of endosulfan and elevated temperature and fed with control diet (T(2)), fish subjected to endosulfan and elevated temperature and fed with choline-supplemented diet (T(3)), fish subjected to endosulfan and temperature and fed with betaine-supplemented feed (T(4)), and fish subjected to endosulfan and temperature and fed with lecithin-supplemented feed (T(5)). The result shows that in both the groups, that is, endosulfan exposed and concurrent exposure to endosulfan and elevated temperature group of L. rohita the growth performance like percentage weight gain, feed conversion ratio and specific growth rates were significantly different (P?相似文献   

Bioavailability of co‐supplemented organic and inorganic zinc and selenium sources in a white fishmeal‐based rainbow trout (Oncorhynchus mykiss) diet

The bioavailability of trace elements in fishmeal diets is influenced by their chemical forms and dietary anti‐nutritional factors. In formulated fish feed, supplemented organically bound minerals may be more bioavailable than inorganic minerals. A 10‐week feeding trial was undertaken with rainbow trout (Oncorhynchus mykiss) to determine whether the inclusion of organically bound selenium (Se) and zinc (Zn) improved uptake and assimilation of these elements compared to commonly used inorganic forms. The three diets tested included a control diet, no added Zn or Se; an organic Se‐yeast and Zn‐proteinate supplemented diet; and an inorganic sodium selenite and Zn‐sulphate supplemented diet. The endpoints tested were apparent digestibility, whole body levels, tissue distribution and Se‐ and Zn‐dependent enzyme activities. Digestibility of residual Se in the basal diet was 54.2 ± 1.0% and supplemented Se‐yeast was significantly more digestible than selenite (p < 0.05). Digestibility of residual Zn was 21.9 ± 2.0% and no significant difference was found between the treatments (p = 0.89). Whole body Se was raised by both Se sources and to a greatest extent by Se‐yeast (p < 0.001). Zn‐sulphate, and to a lesser extent Zn‐proteinate, both raised whole body Zn (p < 0.05). Dietary Zn in the basal diet was found to be above requirements, yet Zn‐sulphate had a significantly greater retention than Zn‐proteinate in those tissues that responded to Zn supplementation. Se‐yeast significantly raised Se in all tissues to a greater extent than selenite, except in the pyloric caeca and liver where the greatest increases were by selenite. Only Se‐yeast elevated Se‐dependent thioredoxin reductase activity (p < 0.05) and neither forms of Se affected glutathione peroxidise activity (p = 0.059). Alkaline phosphatase and carboxypeptidase B were not affected by Zn supplementation (p = 0.51 and p = 0.88 respectively). In all aspects, Se‐yeast was found to be a highly bioavailable form of Se in comparison to selenite. Because of its superior bioavailability, organically bound Se would be a preferred Se source for supplementation of fishmeal trout diets than selenite.     

Post-harvest micro-flora on major cultivars of Indian mangoes

This study examined the surface micro-flora on nine major mango varieties collected from nine states of India in three different harvesting stages (early, mid and late). Mango surface supported substantial microbial component, including various species of bacteria, filamentous fungi and yeasts. Total microbial population was in the range of 10⁵–10⁸ and was significantly different in different cultivars as well as harvesting stages. However, all the mango varieties invariably showed highest microbial population in third harvesting stage. Comparative microbial population of yeast, mold and bacteria showed significant variation in different mango varieties at the third harvesting stage except for Alphonso from Maharashtra and Karnataka. Microbial population on mango fruit surface was strongly influenced by climatic factor, stages of fruit development and varietal specificity.     

Remote sensing and machine learning for crop water stress determination in various crops: a critical review

Precision Agriculture - The remote sensing (RS) technique is less cost- and labour- intensive than ground-based surveys for diverse applications in agriculture. Machine learning (ML), a branch of...     

In vivo immunosuppression by synthetic pyrethroid (cypermethrin) pesticide in mice and goats

Cypermethrin toxicity was produced in mice by intra-peritoneal injection of the pesticide at 50 mg/kg body weight per day for 26 days, and in goats by drenching with cypermethrin at 41.6 mg/kg body weight per day for 30 days. The status of cell-mediated immunity (CMI) was assessed by the 2,4-dinitrofluorobenzene (DNFB) skin sensitivity test. The results indicated significant depression of CMI in the cypermethrin-treated mice and goats. In addition, the humoral immune reaction of the goats intoxicated with cypermethrin was estimated by enumeration of the plaque-forming B-lymphocytes. The rate of plaque formation in the lymphocyte suspension of cypermethrin-treated goats was significantly reduced and the diameter of the plaques was also significantly lower than in that of control animals. The results indicated that cypermethrin suppressed both CMI and the antibody-forming ability of lymphocytes. This immunosuppressive action of cypermethrin is being reported for the first time.     

Land-use history drives contemporary pollinator community similarity

Context

Habitat loss, especially within agriculture, can be a threat to biodiversity. However, biodiversity may respond slowly to habitat loss, taking time to undergo successional change following a disturbance. Despite the fact that historic processes often mediate current patterns of biodiversity, most studies focus only on contemporary factors.

Objectives

Our research examines how both contemporary and historic environmental factors impact current pollinator community similarity, or beta-diversity. We examine two hypotheses: H1) contemporary land-use predicts community similarity, but also that land-use history has long-lasting effects on beta-diversity; H2) the specific response to contemporary and historic environmental factors is explained by variation in pollinator species life-history traits.

Methods

We sampled 36 pollinator communities over a three-year period across cotton fields varying in historic and contemporary land-use. Using multiple regression on distance matrices (MRDM), we investigate correlations between community similarity and differences in contemporary and historic environmental factors.

Results

First, we show that increased time between sampling events and the loss of semi-natural habitat over a 19-year period led to decreased community similarity. Interestingly, neither geographic distance nor contemporary environmental factors contributed to similarity. Second, we show that much of the variation in community similarity is due to variation in pollinator species life-history traits, such as foraging ability and diet breadth.

Conclusions

Results indicate that land-use history has long-lasting effects on community composition, greater than effects exhibited by contemporary factors. These legacy effects are critical considerations for conservation as their omission may lead to overly optimistic assessments of biodiversity in recently disturbed habitats.