Control of Negative Gravitropism and Tension Wood Formation by Gibberellic Acid and Indole Acetic Acid in Fraxinus mandshurica Rupr. var. japonica Maxim Seedlings

In the present study, we Investigated the role of glbberelllc acid （GA3） and Indole acetic acid （IAA） In the gravity response of stems and tension wood formation using two-year-old stems of Fraxinus mandshurica Rupr. var. Japonica Maxim seedlings. Forty-five seedlings were used and divided Into nine groups that Included five seedlings In each group. Seedlings were treated with applications of GA3 alone at concentrations of 2.89×10^-8 and 2.89×10^-7 μmol/L, IAA alone at concentrations of 5.71×10^-8 and 5.71×10^-7 μmol/L, or their combination to the apical bud of the stem using a mlcroplpette. Seedlings were positioned horizontally after the first treatment. The same treatments were repeated six times per week. At the end of the experiment, all seedlings were harvested. Then, stem segments were cut under a light microscope. Application of exogenous GA3 at the higher concentration stimulated the upward bending of stems, whereas exogenous IAA had no effect. A synergistic effect of GA3 and IAA on upward stem bending was observed following application of the two combinations of GA3 and IAA. Moreover, application of exogenous GA3 at the higher dose stimulated wood formation on both the upper and lower sides of the stems, whereas the mixture of GA3 and IAA had a synerglstic effect on wood formation In horizontal stems. Application of exogenous IAA alone at the lower concentration （5.71×10^-8 μmol/L） or application of a mixture of the higher concentrations of GA3 （2.89×10^-7 μmol/L） and IAA （5.71×10^-7 μmol/L） Inhibited the development of gelatinous fibers （the G-layer） of tension wood on the upper side of the horizontal stems. The differentiation of gelatinous fibers of tension wood was not Inhibited by GA3 when It was applied alone, whereas the development of the gelatinous fibers of tension wood was strongly affected by the application of IAA. The findings of the present study suggest that the development of the G-layer Is not related to the dose of GA3, but needs a relatively lower concentration of IAA.

Endophytes from medicinal plants and their potential for producing indole acetic acid, improving seed germination and mitigating oxidative stress

Medicinal plants have been used by marginal communities to treat various ailments. However, the potential of endophytes within these bio-prospective medicinal plants remains unknown. The present study elucidates the endophytic diversity of medicinal plants（Caralluma acutangula, Rhazya stricta, and Moringa peregrina） and the endophyte role in seed growth and oxidative stress. Various organs of medicinal plants yielded ten endophytes, which were identified as Phoma sp.（6 isolates）, Alternaria sp.（2）, Bipolaris sp.（1）, and Cladosporium sp.（1） based on 18 S rD NA sequencing and phylogenetic analysis. The culture filtrates（CFs; 25%, 50%, and 100% concentrations） from these endophytes were tested against the growth of normal and dwarf mutant rice lines. Endophytic CF exhibited dose-dependent growth stimulation and suppression effects. CF（100%） of Phoma sp. significantly increased rice seed germination and growth compared to controls and other endophytes. This growth-promoting effect was due to the presence of indole acetic acid in endophytic CF. The gas chromatography/mass spectrometry（GC/MS） analysis showed the highest indole acetic acid content（（54.31±0.21） μmol/L） in Bipolaris sp. In addition, the isolate of Bipolaris sp. exhibited significantly higher radical scavenging and anti-lipid peroxidation activity than the other isolates. Bipolaris sp. and Phoma sp. also exhibited significantly higher flavonoid and phenolic contents. The medicinal plants exhibited the presence of bio-prospective endophytic strains, which could be used for the improvement of crop growth and the mitigation of oxidative stresses.

Effect of Inoculation with Three Phytohormone Producers Phytobacteria with ACC Deaminase Activity on Root Length of Lens esculenta Seedlings

Plant-associated bacteria that inhabit the rhizosphere may influence the plant growth by their contribution to the endogenous pool of phytohormones and by the activity of ACC deaminase to decrease the ethylene concentration. The aim of this study was to analyse the root length growth by the promoting effect of indole acetic acid producers phytobacteria with ACC deaminase activity, on inoculated seeds of Lens esculenta as synergistic effect on root elongation. In this study, although the roots of L. esculenta seedlings do not show a significant promotion, these phytobacteria could be recommended to treat plants analyzing their added inoculum to increase plant biomass and retard the effect of ethylene on cultures supplied with Tryptophan and ACC.

Characterization of 1-Aminocyclopropane-1-Carboxylate(ACC) Deaminase-Containing Pseudomonas spp.in the Rhizosphere of Salt-Stressed Canola

When exposed to biotic or abiotic stress conditions, plants produce ethylene from its immediate precursor 1-aminocyclopropane-1- carboxylate （ACC）, leading to retarded root growth and senescence. Many plant growth-promoting rhizobacteria contain the enzyme ACC deaminase and this enzyme can cleave ACC to form a-ketobutyrate and ammonium, thereby lowering levels of ethylene. The aim of this study was to isolate and characterize ACC deaminase-producing bacteria from the rhizosphere of salt-stressed canola （Brassica napus L.）. Out of 105 random bacterial isolates, 15 were able to utilize ACC as the sole source of nitrogen. These 15 isolates were also positive for indole acetic acid （IAA） production. Phylogenetic analysis based on partial 16S rDNA sequences showed that all isolates belonged to fluorescent Pseudomonas spp. In the canola rhizosphere investigated in this study, Pseudomonas fluorescens was the dominant ACC deaminase-producing species. Cluster analysis based on BOX-AIR-based repetitive extragenic palindromic-polymerase chain reaction （BOX-PCR） patterns suggested a high degree of genetic variability in ACC deaminase-producing P. fluorescens strains. The presence of indigenous ACC-degrading bacteria in the rhizosphere of canola grown in saline soils indicates that these bacteria may contribute to salinity tolerance.

Effect of Plant Growth-Promoting Rhizobacteria on Growth,Nodulation and Nutrient Accumulation of Lentil Under Controlled Conditions

Application of plant growth-promoting rhizobacteria （PGPR） has been shown to increase legume growth and development under field and controlled environmental conditions. The present study was conducted to isolate plant growth-promoting rhizobacteria （PGPR） from the root nodules of lentil （Lens culinaris Medik.） grown in arid/semi-arid region of Punjab, Pakistan and examined their plant growth-promoting abilities. Five bacterial isolates were isolated, screened in vitro for plant growth-promoting （PGP） characteristics and their effects on the growth of lentil were assessed under in vitro, hydroponic and greenhouse （pot experiment） conditions. All the isolates were Gram negative, rod-shaped and circular in form and exhibited the plant growth-promoting attributes of phosphate solubilization and auxin （indole acetic acid, IAA） production. The IAA production capacity ranged in 0.5-11.0μg mL-1 and P solubilization ranged in 3-16 mg L-1. When tested for their effects on plant growth, the isolated strains had a stimulatory effect on growth, nodulation and nitrogen （N） and phosphorus （P） uptake in plants on nutrient-deficient soil. In the greenhouse pot experiment, application of PGPR significantly increased shoot length, fresh weight and dry weight by 65%, 43% and 63% and the increases in root length, fresh weight and dry weight were 74%, 54% and 92%, respectively, as compared with the uninoculated control. The relative increases in growth characteristics under in vitro and hydroponic conditions were even higher. PGPR also increased the number of pods per plant, 1 000-grain weight, dry matter yield and grain yield by 50%, 13%, 2870 and 29%, respectively, over the control. The number of nodules and nodule dry mass increased by 170% and 136%, respectively. After inoculation with effective bacterial strains, the shoot, root and seed N and P contents increased, thereby increasing both N and P uptake in plants. The root elongation showed a positive correlation （R2 = 0.67） with the IAA production and seed yield exhibited a positive correlation （R2 = 0.82） with root nodulation. These indicated that the isolated PGPR rhizobial strains can be best utilized as potential agents or biofertilizers for stimulating the growth and nutrient accumulation of lentil.