Effects of chromium stress on the subcellular distribution and chemical form of Ca,Mg, Fe,and Zn in two rice genotypes

A hydroponic experiment was carried out to study effects of chromium (Cr) stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes differing in Cr accumulation. The results showed that Ca, Mg, Fe, and Zn ions were mainly located in cell walls and vacuoles in roots. However, large amounts of metal ions were transferred from the vacuole to the nucleus and to other functional organelles in shoots. Chromium concentrations in the nutrient solution of 50 μM and above significantly decreased Ca concentrations in the chloroplast/trophoplast, the nucleus, and in mitochondria. It further increased Mg concentrations in the nucleus and in mitochondria, as well as Zn and Fe concentrations in the chloroplast/trophoplast. These Cr‐induced changes in ion concentrations were associated with a significant reduction in plant biomass. It is suggested that Cr stress interferes with the functions of mineral nutrients in rice plants, thus causing a serious inhibition of plant growth. The chemical forms of the four nutrients were determined by successive extraction. Except for Ca, which was mainly chelated with insoluble phosphate and oxalic acid, Mg, Zn, and Fe were extractable by 80% ethanol, d‐H₂O, and 1μM NaCl. The results indicated that these low–molecular weight compounds, such as organic acids and amino acids, may play an important role in deposition and translocation of Mg, Zn, and Fe in the xylem system of rice plants.     

Chemically Modified Crop Residues as a Low-Cost Technique for the Removal of Heavy Metal Ions from Wastewater

Batch adsorption experiments were carried out to evaluate the effect of type of crop residues and chemical pretreatment solutions on the removal efficiency of heavy metal ions at different concentrations of synthetic wastewater solutions. Rice straw, cotton stalks, and maize stalks were pretreated with different solutions (i.e., sulfuric acid, oxalic acid, sodium hydroxide, and distilled water as the control treatment) in order to increase their metal-binding capacity. Results indicated that cotton stalks were the best biosorbent material according to their efficiency in removal of heavy metal ions. Sodium hydroxide was the best chemical pretreatment method for stimulating the biosorption capacity of crop residues. Ions of Pb²⁺ had the highest biosorption ratio among all competitive ions, whereas Mn²⁺ ions had the lowest. The removal efficiency decreased as the concentration of heavy metal ions increased in aqueous solutions. Sorption equilibrium isotherms could be described by the Langmuir model in most cases, whereas an isotherm of S shape was observed in other cases, which did not follow the Langmuir isotherm model. In conclusion, cotton stalks pretreated with sodium hydroxide could be used as an efficient technique for wastewater remediation prior to irrigation due to its low-cost, little processing, and high biosorption capacity.     

Phosphorus Requirements of Rice Grown in Soils With Different Sodicity

ABSTRACT

Phosphorus (P) fertilization is reported to alleviate the adverse effects of sodicity on survival of the seedlings, growth, and yield of rice. However, it is not known if required levels of Olsen's P to alleviate the adverse sodicity effects varies with increased sodicity stress. The present study, conducted at various pH values (8.0, 9.3, 9.7, and 9.9) with varying levels of P fertilization (P0.0, P0.2, P0.4, P0.6, and P0.8 kg hm^{? 2}), showed that P requirements of rice increased with increases in sodicity stress. At a pH of 8.0, 4.3 mg kg^{? 1} Olsen's P was sufficient for survival of the seedlings, but not for grain weight (6.3 mg kg^{? 1}). Seedlings required 7.0 and 9.5 mg kg^{? 1}Olsen's P to survive at pH 9.7 and 9.9, respectively. Similarly, high P levels were needed for more total and fertile tillers and spikelets numbers. One thousand (1000) grain weight and grain yield responded to 6.3, 7.7, 8.8, and 10.4 mg kg^{? 1} Olsen's P at pH values of 8.0, 9.3, 9.7, and 9.9, respectively. Total chlorophyll in the leaves was significant in P fertilized plants. At a pH of 9.7, plants with 7.9 mg kg^{? 1} Olsen's P had 52% more chlorophyll per 100 ppm sodium (Na) in the leaves compared to those at 6.3 mg kg^{? 1} Olsen's P. This could possibly be due to improved tissue tolerance to Na in P-fertilized plants. Plants fertilized with P had higher P and potassium (K) concentrations in their shoots. Olsen's P levels of 7.7 mg kg^{? 1}, 7.9 mg kg^{? 1}, and 9.5 mg kg^{? 1} were effective in restricting increases of Na (a potentially toxic ion) in shoots at pH 9.3, 9.8, and 9.9, respectively, thus helping plants have better yields.     

Interactive effects of biochar and micronutrients on faba bean growth,symbiotic performance,and soil properties

Leguminous crops are significantly involved in the global symbiotic biological N₂ Fixation (BNF), an eco‐friendly process in the agriculture system. Biochar is considered as a vital amendment in improving growth and quality of crops and soils. Few investigations have been conducted to determine the combination effect of biochar with microelements on growth of legumes and soil properties. This study was designed to study the effect of soybean straw‐derived biochar (SSDB) with or without microelements on soil microbial and chemical properties, growth, yield, and seed chemical composition of faba bean (Vicia faba L.). Results revealed that dehydrogenase (DHA) and phosphatase (P‐ase) activities were markedly improved with the increase of SSDB rates under addition of microelements and their highest values were recorded after 90 d. Significant increases were noticed in nodulation activities, nodulation numbers (30.1–72.8), concentrations of N (1.62–1.93%), P (0.15–0.21%), and K (0.53–0.67%), and seed chemical constituents due to the addition of SSDB in the presence of microelements. Moreover, the combination of biochar with microelements caused significant changes in microbial counts. Overall, this investigation shows the potential and role of SSDB in enhancing the growth quality of faba bean seeds as well as an improvement of soil characteristics.     

Crop sequences and fertilization affect soil vital enzyme activities

This experiment was conducted in split plots based on randomized complete block design with three replications. Three crop sequences: (R1): chickpea, sunflower, wheat, and canola; (R2): green manure, chickpea, green manure, wheat, green manure, and canola; (R3): canola, wheat, and canola were used as main plots. Sub plots consisted of six methods of fertilization: (N1): farmyard manure; (N2): compost; (N3): chemical fertilizers; (N4): farmyard manure + compost; (N5): farmyard manure + compost + chemical fertilizers; and (N6): control. Results showed that the enzyme activities were higher in the N4 treatment. The highest amount of acid phosphatase, protease, dehydrogenase activity, and grain yield was observed in R2 sequence. The highest urease activity (58.6 µg g^?1 h^?1) was obtained in R2N4 treatment. In R2N4 treatment using in-farm inputs, a non chemical fertilizer system can be carried out to improve soil biological activity.     

Morphological variation within collections of Moroccan almond clones and Mediterranean and North American cultivars

Summary Cultivated almonds (Prunus dulcis (Miller) D.A. Webb) in Morocco are still propagated from seeds by farmers to overcome transplant failure of grafted trees. Almond collections in southern Morocco conducted since 1975 have resulted in the selection of clones planted at 3 experimental stations. Principal component analysis (PCA) was used to compare kernel, nut, leaf, and growth habit characteristics among 67 selected Moroccan clones and 14 introduced cultivars. Clustering of clones from similar countries and collection areas would suggest the existence of different almond populations. The Moroccan clones did not cluster separately from the foreign cultivars. Three Moroccan clones had exceptionally large nuts and kernels while 7 selections had high yield potential due to high spur density. Moroccan selections tended to be characterized by small leaves in comparison to foreign cultivars. No evidence was found to suggest the existence of separate populations within the Moroccan almond germplasm.     

Evaluation of proline analysis and chlorophyll fluorescence quenching measurements as drought tolerance indicators in durum wheat (Triticum turgidum L. var. durum)

Summary The possibility of using proline accumulation and fluorescence inhibition as predictive tests for drought tolerance in durum wheat has been investigated. The drought susceptibility of 25 genotypes was evaluated by comparing yields and yield components in irrigated and non irrigated conditions in the field. A drought susceptibility index (DSI) was calculated based on yields from irrigated and dry treatments and compared with the results obtained using the two physiological criteria. Proline accumulation and chlorophyll fluorescence inhibition were found to be significantly and negatively correlated with DSI of grain yield, biological yield, and thousand kernel weight, and tiller index. The use of both criteria for breeding durum wheat in Mediterranean dryland is discussed.     

Field evaluation and fiber analysis of transgenic cotton

We report the field evaluation of second generation of transgenic cotton expressing Bacillus thuringiensis (Bt) genes cry1Ac and cry2A under CaMV 35S promoter. Sixty-five transgenic lines were grown under RCBD design. Transgenic plants exhibited inherent ability to resist target insect (p < 0.05 and 0.01). Morphological studies showed significant reduction in plant height making them favorable for breeding. Yield was significantly increased for the transgenic lines. Fiber analysis showed improved gin turn out 40% for transgenic lines in comparison to 32% for non-transformed lines. Fibre quality of transgenic lines was not affected when compared with non transgenic lines. Inheritance pattern for transgenic lines suggests the need of further studies to understand the complex molecular mechanisms for resistance management and biosafety studies to develop new Bt cotton varieties.     

Inheritance of race 1.2 Fusarium wilt resistance in four melon cultivars

The resistance to Fusarium oxysporum f.sp. melonis (Fom) race 1.2 has been studied in melons, such as the Portuguese accession ‘BG-5384’ and in the Japanese ‘Shiro Uri Okayama’, ‘Kogane Nashi Makuwa’, and ‘C-211’, since a good characterization of the resistance is necessary before its introgression into commercial varieties. These four melon accessions showed a high level of resistance to races 0, 1, and 2 of Fom, indicating that the partial resistance to the race 1.2 previously detected may not have been race specific. To determine the mode of inheritance of the resistance to Fom race 1.2, the F₁, F₂, BCP_R, and BCP_S generations from the crosses between the four resistant accessions above and ‘Piel de Sapo’, a Fom race 1.2 susceptible melon, were developed. They were subsequently inoculated with two Fom isolates, one from the pathotype 1.2Y and the other from the pathotype 1.2W. The area under the disease progress curve was determined for each inoculated plant, and the data were analyzed. We show that the resistance seen in these accessions is polygenically inherited with a complex genetic control because many epistatic interactions were detected. The three epistatic effects; additivity × additivity, dominance × dominance, and dominance × additivity are present and significant, with differing magnitudes from one cross to the next. The relatively low heritabilities, and these epistatic effects make difficult the improvement of the resistance, from these sources, through a standard selection procedure.