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Field experiments were conducted at the Agricultural College and Research Institute (Killikulam), Tamil Nadu Agricultural University from September 1992 to June 1995 to optimize the herbicide dose and application techniques for cotton-based intercropping systems.283

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The present study was carried out for developing an efficient in vitro callus induction and plant regeneration system in four different tomato genotypes (Solanum lycopersicum Mill., previous name: Lycopersicon esculentum), Advantage II, Edkawy, Castle Rock and Super Strain B, using hypocotyl and cotyledon explants. The effects of two cytokinins, BA (benzyl adenine) and Kin (kinetin), on callus induction and plant regeneration frequency were investigated when added to MS medium in combination at varying concentrations. All concentrations of the two cytokinins were suitable for callus induction and plant regeneration. The frequency of callus induction and plant regeneration from both cotyledon and hypocotyl explants reached 100% for all tested genotypes. Cotyledons produced a higher average number of shoots per explants than hypocotyls for all the genotypes in the five concentrations of combined cytokinins. The average number of shoots per explant in Super Strain B was found to be the highest (42 and 60 for the hypocotyl and cotyledon explants, respectively). Supplementing MS medium with 1.0 mg L−1 kinetin and 1.0 mg L−1 benzyl adenine was found to be optimum for producing the highest number of shoots per explant from hypocotyls and cotyledons in the tomato genotypes investigated. The proposed medium showed a significant superiority over the reference media.

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Water stress is a severe limitation for crop growth especially in arid and semi-arid regions of the world, as it has a vital role in plant growth and development at all growth stages. The aim of the present study was to evaluate the differential responses of twelve sunflower genotypes to three levels of water supply and select the most suitable one for such conditions. Two field experiments were conducted under adequate (7140 m3/ha), moderate (4760 m3/ha) and severe (2380 m3/ha) water regimes to evaluate the chlorophyll index, transpiration rate, leaf water content, plant height, head diameter, seeds/head, 1000-seed weight, seed and oil yield of the genotypes. Moderate and severe levels of drought had a significant impact on the transpiration rate, leaf water content, yield-contributing characters and oil yield of all the sunflower genotypes. However, the sunflower genotypes showed different responses to the different water regimes. The highest seed and oil yields were attained in L990 and Giza 102 in the case of adequate water supplies, while L38 was the best under moderate and severe drought conditions. On the basis of the results, sunflower genotype L990 could be recommended for growing when adequate water supplies are available, and L38 under moderate and severe water regimes to obtain high seed and oil yields.

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The B(S) genome diploids (2n = 2x = 14) are a unique reservoir of genetic diversity that can provide wheat breeders a rich source of allelic variation for stress traits that limit productivity. Restricted in practical use essentially due to their complex chromosomal behavior, these diploids have been in limited practical usage. The classic utilization example has been the suppression activity of the Ph locus and role in alien genetic transfer aspects that has been a standard in cytogenetic manipulation studies. For applied efforts focusing on Aegilops speltoides researchers in CIMMYT initiated an ambitious program to make AABBBB(SS) synthetics and made progress by generating over 50 such synthetics. Of these 20 were available for this study in which phenology and powdery mildew screening were evaluated. Four of these 20 synthetics appeared to be useful sources for further exploitation in breeding. These were entries 6, 9, 10 and 11 suited for exploitation in pre-breeding, with positive phenological characters particularly high thousand-kernel weight and are cytologically near euploid at 2n = 6x = 42. The subtle hyper (43) and hypoploid number would not negate their applied use potential. Preference however goes to genotypes 9 and 11.

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The main aim of this study was to evaluate the appropriateness of using different diversity indices for conservation purposes in arid environments. The study was done on Mt Serbal as a case study representing mountainous arid areas. Mt Serbal is one of the richest and most diverse areas in Egypt. It was sampled by 97 stands representing different vegetation cover, land-forms and habitats. Species density and environmental factors (including altitude, slope, soil texture, hygroscopic moisture, water holding capacity, pH, EC, and soil organic matter content) were recorded or measured in each stand. The results reveal that Mt Serbal is characterised by a high diversity of plant species and the most diverse area is Shaq Sha’rany. The study recommends Margalef and species richness as the most suitable to measure the diversity at different localities, land-forms, and vegetation groups. It emphasises on the necessity of reporting on species richness in any conservational study. Meanwhile, indices that are excessively sensitive to change in sample size, gear, or handling procedures should be avoided.

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grains of wheat (Triticum aestivumL. cv. Raj-3077) were soaked in 0, 10-5, 10-4or 10-3 M aqueous solutions of salicylic acid (SA) for 3, 6 or 9 h. The seedlings raised from grains pre-treated with 10-5 M SA possessed significantly higher leaf number, fresh and dry mass per plant, and nitrate reductase and carbonic anhydrase activities 30 and 40 days after sowing. However, 10-3 M SA reduced all the above-mentioned parameters.

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Higher plant population and nitrogen management is an adopted approach for improving crop productivity from limited land resources. Moreover, higher plant density and nitrogen regimes may increase the risk of stalk lodging, which is a consequence of complex interplant competition of individual organs. Here, we aimed to investigate the dynamic change in morphology, chemical compositions and lignin promoting enzymes of the second basal inter-nodes altering lodging risk controlled by planting density and nitrogen levels. A field trial was conducted at the Mengcheng research station (33°9′44″N, 116°32′56″E), Huaibei plain, Anhui province, China. A randomized complete block design was adopted, in which four plant densities, i.e., 180, 240, 300, and 360 × 104 ha−1 and four N levels, i.e., 0, 180, 240, and 300 kg ha−1 were studied. The two popular wheat varieties AnNong0711 and YanNong19 were cultivated. Results revealed that the culm lodging resistance (CLRI) index of the second basal internodes was positively and significantly correlated with light interception, lignin and cellulose content. The lignin and cellulose contents were significantly and positive correlated to light interception. The increased planting density and nitrogen levels declined the lignin and its related enzymes activities. The variety AnNong0711 showed more resistive response to lodging compared to YanNong19. Overall our study found that increased planting densities and nitrogen regimes resulted in poor physical strength and enzymatic activity which enhanced lodging risk in wheat varieties. The current study demonstrated that stem bending strength of the basal internode was significantly positive correlated to grains per spike. The thousand grain weight and grain yield had a positive and significant relationship with stem bending strength of the basal internode. The results suggested that the variety YanNong19 produces higher grain yield (9298 kg ha−1) at density 240 × 104 plants ha−1, and 180 kg ha−1 nitrogen, while AnNong0711 produced higher grain yield (10178.86 kg ha−1) at density 240 × 104 plants ha−1 and with 240 kg ha−1 nitrogen. Moreover, this combination of nitrogen and planting density enhanced the grain yield with better lodging resistance.

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Field crops are subjected to numerous inconsiderate climatic hazards that negatively affect physiological processes, growth and yield. Drought is one of the major abiotic factors that limits the agricultural productivity especially in the arid and semi-arid areas of the globe. Silicon (Si) is a naturally occurring beneficial nutrient which modulates plant growth and development events and has been known to improve the crop tolerance to abiotic stresses. With the objective to investigate the role of silicon nutrition on maize hybrids under limited moisture supply, a two year field study was conducted during 2010–11 at Post Graduate Research Station (PARS), University of Agriculture Faisalabad, Pakistan. We evaluated growth of two maize hybrids P-33H25 and FH-810 under well watered (100% field capacity) and water deficit situation (60% field capacity) as affected by Si application. Silicon was added in soil @ 100 mg/kg using Calcium Silicate as source. Water deficit condition significantly reduced agro-morphological and physiological attributes of maize plants. Silicon application significantly increased the plant height, leaf area index, yield and related attributes along with improvement in photosynthetic rate, leaf water status and osmotic adjustment under limited moisture supply. It was concluded that silicon application to droughtstressed maize enhanced its growth and yield owing to improved photosynthetic rate, higher osmotic adjustment, increased water status and lowered transpiration.

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Vegetation in natural desert and agro-ecosystems was investigated in the middle sector of Egypt. The vegetation was classified by the Two Way Indicator Species Analysis technique (TWINSPAN) into nine vegetational groups representing seven habitat types: desert, fallow land, winter crops of old cultivated land, summer crops of old cultivated land, Citrus orchards, winter crops of reclaimed land, and summer crops of reclaimed land. Detrended Canonical Correspondence Analysis (DCCA) demonstrates that soil factors especially soil texture, CaCO3, organic carbon and electric conductivity contribute significantly to the distribution of species. In all habitat types, species diversity is higher in winter than in summer season. The weed species diversity is greater in the reclaimed areas compared to the old cultivated land and in winter crops than in summer ones.

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Introduction

Endophytic fungi associated with desert plants have a crucial role to enable these plants to tolerate abiotic stress, such as heat and drought.

Methods

In this study, a thermophilic fungal endophyte was isolated from a hot desert-adapted plant, Cullen plicata Delile. The endophytic fungus was (molecularly) identified as Thermomyces lanuginosus, and inoculated plants were coded as E+ and the control as E−.

Results

This fungus had an effective growth-promoting activity on its host plant and increased the plant resistance to heat stress as well.

Discussion

Our findings demonstrate that thermophilic fungal endophytes can enhance drought and heat stress tolerance in desert plants by ecophysiological mechanisms and improve growth of its host plants.

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