Role of microbial inoculants as bio fertilizers for improving crop productivity: A review.

The world's population is increasing and is anticipated to spread 10 billion by 2050, and the issue of food security is becoming a global concern. To maintain global food security, it is essential to increase crop productivity under changing climatic conditions. Conventional agricultural practices frequently use artificial/chemical fertilizers to enhance crop productivity, but these have numerous negative effects on the environment and people's health. To address these issues, researchers have been concentrating on substitute crop fertilization methods for many years, and biofertilizers as a crucial part of agricultural practices are quickly gaining popularity all over the globe. Biofertilizers are living formulations made of indigenous plant growth-promoting rhizobacteria (PGPR) which are substantial, environment-friendly, and economical biofertilizers for amassing crop productivity by enhancing plant development either directly or indirectly, and are the renewable source of plant nutrients and sustainable agronomy. The review aims to provide a comprehensive overview of the current knowledge on microbial inoculants as biofertilizers, including their types, mechanisms of action, effects on crop productivity, challenges, and limitations associated with the use of microbial inoculants. In this review, we focused on the application of biofertilizers to agricultural fields in plant growth development by performing several activities like nitrogen fixation, siderophore production, phytohormone production, nutrient solubilization, and facilitating easy uptake by crop plants. Further, we discussed the indirect mechanism of PGPRs, in developing induced system resistance against pest and diseases, and as a biocontrol agent for phytopathogens. This review article presents a brief outline of the ideas and uses of microbial inoculants in improving crop productivity as well as a discussion of the challenges and limitations to use microbial inoculants.

Assessing the response of five tree species to air pollution in Riyadh City, Saudi Arabia, for potential green belt application.

Tree species (including Eucalyptus camaldulensis, Ziziphus spina-christi, Albizia lebbeck, Prosopis juliflora, Pithecellobium dulce, and Ficus altissima) were investigated to elucidate their appropriates for green belt application. Leaf samples were collected from four different locations in Riyadh: (1) residential; (2) dense traffic; (3) industrial; and (4) reference sites located approximately 20 km away from the city of Riyadh. Leaves collected from the industrial site showed the highest leaf area reduction. The smallest reduction of leaf areas was observed for F. altissima (11.6%), while the highest reduction was observed for P. juliflora (34.8%). Variations in the air pollution tolerance index (APTI) coupled with the anticipated performance index (API) for each species were examined. The APTI value of Z. spina-christi was highest (58.5) at the industrial site while the lowest APTI value was for P. juliflora (14) at the reference site. Correlation coefficient and linear regression analyses determined that the correlation between the ascorbic acid content and APTI is positive and significantly strong. Our findings indicate that urban green planning in Riyadh should include growing F. altissima on roadsides as well as in heavy industrial locations followed by Z. spina-christi and A. lebbeck according to their API and APTI performances.

Biomass allocation in Ziziphus spina-christi and the invasive species Prosopis juliflora / Alocação de biomassa em Ziziphus spina-christi e espécies invasoras Prosopis juliflora

Invasion by the exotic species Prosopis juliflora has become a major threat to native plants in Saudi Arabia as the species continues its spread into different regions of the country. Ziziphus spina-christi is a native tree that is common in Saudi Arabia. The objective of this study was to determine how both species would benefit from the availability of sufficient resources without competition. To gain a better understanding of growth under such conditions, a greenhouse experiment was conducted in which seedlings of both species were grown under favorable conditions for 6 months. During this period, growth performance was evaluated three times at intervals of 30, 90, and 180 days. Growth performance varied between the two species during one or more of the studied periods. Significant differences between the species were observed for root mass fraction, number of root tips, root to shoot ratio, height, stem diameter, stem dry weight, stem mass fraction, leaf area, leaf mass fraction, and chlorophyll a and b contents. The relative growth rate (RGR) and relative height growth rate were higher in P. juliflora at 30­90 days, whereas leaf area ratio and net assimilation rate were higher for Z. spina-christi at 90­180 days. Remarkably, the RGR for diameter in P. juliflora was almost double that in Z. spina-christi at 30­90 days and 90­180 days. The results obtained reflect a strategic difference in the biomass allocation to different plant components by the two species, whereby P. juliflora allocates higher biomass to the stems and Z. spina-christi allocates higher biomass to the roots.

Invasão pela espécie exótica Prosopis juliflora tornou-se uma grande ameaça para plantas nativas na Arábia Saudita à medida que a espécie continua a sua propagação em diferentes regiões do país. A Ziziphus spina-christi é uma árvore nativa que é comum na Arábia Saudita. O objetivo deste estudo foi determinar como ambas as espécies se beneficiariam com a disponibilidade de recursos suficientes sem competição. Para se obter uma melhor compreensão do crescimento nestas condições, foi conduzida uma experiência em estufa em que as plântulas de ambas as espécies foram cultivadas em condições favoráveis durante 6 meses. Durante este período, o desempenho de crescimento foi avaliado três vezes em intervalos de 30, 90 e 180 dias. O desempenho do crescimento variou entre as duas espécies durante um ou mais dos períodos estudados. Diferenças significativas entre as espécies foram observadas para a fração de massa da raiz, número de pontas de raiz, razão entre a raiz e a parte aérea, altura, diâmetro do caule, peso seco do caule, fração de massa do caule, área foliar, fração de massa foliar e teor de clorofila a e b. A taxa de crescimento relativo (RGR, relative growth rate) e a taxa relativa de crescimento em altura foram maiores em P. juliflora no período 30-90 dias, enquanto que a razão foliar e a taxa de assimilação líquida foram maiores para Z. spina-christi no período 90-180 dias. Notavelmente, a RGR para o diâmetro em P. juliflora foi quase o dobro da de Z. spina-christi aos 30-90 dias e 90-180 dias. Os resultados obtidos refletem uma diferença estratégica na alocação de biomassa para diferentes componentes das plantas pelas duas espécies, sendo que P. juliflora aloca uma biomassa mais alta para as hastes e Z. spina-christi aloca uma biomassa mais alta para as raízes.