What Is Biotic And Abiotic Influence Plant Growth?

Biotic and abiotic stresses influence plant growth and yield. The narrow layer of soil surrounding roots where essential root metabolism and activities take place is known as rhizosphere. The biology and chemistry of the soil is determined by the root excretion in rhizosphere (~1 mm broad region, has no definite edge). Hiltner was the first person to use this term rhizosphere and expressed it as the distinct zone of soil where microbial population develops due to exudation of root (Hartmann et al. 2008). A large population of microorganisms including bacteria, fungi, protozoa and algae extensively interacts with roots of plant in the rhizosphere. The density of bacterial population is tremendous in the rhizosphere so it is speculated that bacteria …show more content…
Plant Growth Promoting Rhizobacteria (PGPR) is a group of bacteria that exists naturally in the soil and aid in plant’s growth by influencing different plant mechanisms. They actively colonize plant roots and increase plant growth and yield (Wu et al. 2005). PGPRs are widely studied elements for growth of plants under nutrient-stressed environment. PGPRs are beneficial bacteria and elevate nutrient level of plants. They can use different mechanisms to enhance plant growth and development to improve plant stress tolerance and to prevent plants from soil-borne infections. These mechanisms include the production of ACC deaminase in the developing plant’s roots to lessen the level of ethylene (Dey et al. 2004), producing phytohormones (Mishra et al. 2010) and biological N2 fixation (Ardakani et al. 2010). The plants also exhibit antagonistic activity against phytopathogenic microorganisms by producing siderophores, chitinases, b-1,3-glucanase, fluorescent pigment, antibiotics, antifungal metabolites, and/or lytic enzymes, increasing plant nutrients availability via systemic resistance induction (Egamberdieva et al. 2013). PGPRs may use more than one of these mechanisms to improve plant growth. The mechanisms PGPRs use to promote plants growth are not fully understood, but they can be categorized in four groups: a) biofertilizers (solubilisation of mineral …show more content…
Since, over the last few decades, PGPRs utilization for viable agriculture has increased worldwide enormously. Several PGPRs including Enterobacter, Azospirillum, Bacillus, Azotobacter, Pseudomonas, Actinobacter, Bradyrhizobium, etc. are being utilized to produce modernized organic biofertilizers (Vessey 2003). Additionally, P. aeruginosa and P. fluorescens are two highly potent bacterial strains which are generally present in the farm soil (Ganeshan and Manoj Kumar 2005). Effects of PGPRs on the seeds have been realized first time inoculated with Pseudomonas spp. which was isolated from roots. Various studies have been conducted to figure out the influence of PGPRs on plant but very few have considered parameters of seed germination along with plant growth. Plants inoculated with PGPRs give improved growth and resist these stresses significantly better than the uninoculated plants under stress conditions (Kloepper et al. 2007) They also produce different antibiotic compounds which inhibit the proliferation and propagation of plant pathogens (Mazurier et al. 2009). PGPR strain P. fluorescens influence insect’s proliferation at all growth stages. The Corn earthworm, Helicoverpa zea larvae growth was affected by Pseudomonas maltophila that causes more than 60 % decrease in adult emergence and the