Response of Contrasting Rice Genotypes to Zinc Sources under Saline Condition

Abiotic stresses are among the major limiting factors for plant growth and crop productivity.Among these,salinity is one of the major risk factors for plant growth and development in arid to semi-arid regions.Cultivation of salt tolerant crop genotypes is one of the imperative approaches to meet the food demand for increasing population.The current experiment was carried out to access the performance of different rice genotypes under salinity stress and Zinc(Zn)sources.Four rice genotypes were grown in a pot experiment and were exposed to salinity stress(7 dS m^(−1)),and Zn(15 mg kg^(-1)soil)was applied from two sources,ZnSO4 and Zn-EDTA.A control of both salinity and Zn was kept for comparison.Results showed that based on the biomass accumulation and K^(+)/Na^(+)ratio,KSK-133 and BAS-198 emerged as salt tolerant and salt sensitive,respectively.Similarly,based on the Zn concentration,BAS-2000 was reported as Zn-in-efficient while IR-6 was a Zn-efficient genotype.Our results also revealed that plant growth,relative water content(RWC),physiological attributes including chlorophyll contents,ionic concentrations in straw and grains of all rice genotypes were decreased under salinity stress.However,salt tolerant and Zn-in-efficient rice genotypes showed significantly higher shoot K^(+)and Zn concentrations under saline conditions.Zinc application significantly alleviates the harmful effects of salinity by improving morpho-physiological attributes and enhancing antioxidant enzyme activities,and the uptake of K and Zn.The beneficial effect of Zn was more pronounced in salt-tolerant and Zn in-efficient rice genotypes as compared with salt-sensitive and Zn-efficient genotypes.In sum,our results confirmed that Zn application increased overall plant’s performance under saline conditions,particularly in Zn in-efficient and tolerant genotypes as compared with salt-sensitive and Zn efficient rice genotypes.

Biochemical and microbial soil functioning after application of the insecticide imidacloprid

Imidacloprid is one of the most commonly used insecticides in agricultural practice, and its application poses a potential risk for soil microorganisms. The objective of this study was to assess whether changes in the structure of the soil microbial community after imidacloprid application at the field rate（FR, 1 mg/kg soil） and 10 times the FR（10 × FR, 10 mg/kg soil）may also have an impact on biochemical and microbial soil functioning. The obtained data showed a negative effect by imidacloprid applied at the FR dosage for substrate-induced respiration（SIR）, the number of total bacteria, dehydrogenase（DHA）, both phosphatases（PHOS-H and PHOS-OH）, and urease（URE） at the beginning of the experiment. In 10 × FR treated soil, decreased activity of SIR, DHA, PHOS-OH and PHOS-H was observed over the experimental period. Nitrifying and N2-fixing bacteria were the most sensitive to imidacloprid. The concentration of NO3-decreased in both imidacloprid-treated soils,whereas the concentration of NH4＋in soil with 10 × FR was higher than in the control.Analysis of the bacterial growth strategy revealed that imidacloprid affected the r- or K-type bacterial classes as indicated also by the decreased eco-physiological（EP） index.Imidacloprid affected the physiological state of culturable bacteria and caused a reduction in the rate of colony formation as well as a prolonged time for growth. Principal component analysis showed that imidacloprid application significantly shifted the measured parameters, and the application of imidacloprid may pose a potential risk to the biochemical and microbial activity of soils.