[Show abstract][Hide abstract]ABSTRACT: Red light, temperature and gibberellins are well known for their capacity to induce higher germination in dormant seeds of several plant species. In the current study, we investigated the effect of various temperature (10, 13, 16, 19, 22 and 25°C) and gibberellic acid (GA 3) and GA 4+7 concentrations (0.1, 1, 10, and 100 uM) on germination of Poa annua, Alopecurus aequalis and Stellaria aquatica seeds incubated under continuous dark or treated with red light pulse of 80 mol m -2 s -1 red light (660 nm) for 10 min after 12 h of dark period. We found that incubation temperature and gibberellins (GAs) significantly enhanced seed germination in red light treated seeds, as maximum germination was observed for A. aequalis (67.3% at 13°C), P. annua (61.3% at 13°C), and S. aquatica (42% at 19°C) in such treatments. Exogenous GA 4+7 significantly promoted germination of P. annua and A. aequalis seeds, while GA 3 induced higher germination in S. aquatica seeds. It was observed that GAs were more effective in the presence of red light as least germination stimulation was recorded for GAs under dark condition and no germination was found in weed seeds at control and 0.1 mM GA 3 and GA 4+7 treatments. It can be concluded that lower temperature (13°C) and GA 4+7 in conjunctions with red light pulse, induced maximum germination in dormant weed seeds.
Full-text Article · Jan 2012 · AFRICAN JOURNAL OF BIOTECHNOLOGY
[Show abstract][Hide abstract]ABSTRACT: Endophytic fungi are little known for their role in gibberellins (GAs) synthesis and abiotic stress resistance in crop plants. We isolated 10 endophytes from the roots of field-grown soybean and screened their culture filtrates (CF) on the GAs biosynthesis mutant rice line - Waito-C. CF bioassay showed that endophyte GMH-1B significantly promoted the growth of Waito-C compared with controls. GMH-1B was identified as Penicillium minioluteum LHL09 on the basis of ITS regions rDNA sequence homology and phylogenetic analyses. GC/MS-SIM analysis of CF of P. minioluteum revealed the presence of bioactive GA(4) and GA(7). In endophyte-soybean plant interaction, P. minioluteum association significantly promoted growth characteristics (shoot length, shoot fresh and dry biomasses, chlorophyll content, and leaf area) and nitrogen assimilation, with and without sodium chloride (NaCl)-induced salinity (70 and 140 mM) stress, as compared with control. Field-emission scanning electron microcopy showed active colonization of endophyte with host plants before and after stress treatments. In response to salinity stress, low endogenous abscisic acid and high salicylic acid accumulation in endophyte-associated plants elucidated the stress mitigation by P. minioluteum. The endophytic fungal symbiosis of P. minioluteum also increased the daidzein and genistein contents in the soybean as compared with control plants, under salt stress. Thus, P. minioluteum ameliorated the adverse effects of abiotic salinity stress and rescued soybean plant growth by influencing biosynthesis of the plant's hormones and flavonoids.
Full-text Article · Sep 2011 · Journal of Microbiology and Biotechnology
[Show abstract][Hide abstract]ABSTRACT: Seed dormancy is a major constraint in the eradication of weeds from agriculture fields. Seeds of Amaranthus retroflexus, Echinocloa crus-galli and Digitaria adscendens were collected from cultivated fields, dried and then treated with different nitrogen containing compounds i.e., potassium nitrate, ammonium chloride, ammonium nitrate and sodium nitrite. Some seeds were kept under dark while others were irradiated with red light for 10 min., after 12 hr of inhibition. The N-compounds were applied @ 1, 5, 10, 25 and 50 mM, while the strength of red light pulse was maintained at 80μmols -2 m -1 . It was observed that red light significantly improved germination rates of A. retroflexus, E. crus-galli and D. adscendens. Nitrogenous compounds significantly improved germination of weeds and maximum germination was induced by ammonium nitrate. However, exposure of seeds to both red light and N-compounds provided significantly higher germination as compared to singular application of either of them. E. crusgalli recorded highest germination rates in response to red light and N-compounds, while D. adscendens provided least values for the same treatments. Application of N-compounds in conjunction with red light significantly improves germination rates of selected weed species by breaking their dormancy.
Full-text Article · Dec 2010 · Pakistan Journal of Botany
[Show abstract][Hide abstract]ABSTRACT: The beneficial effects of plant growth promoting fungi (PGPF) on plant growth and development are well documented. However,
limited information is available on gibberellin (GA) production capacity of PGPF of endophytic origin. In current study, 11
fungal endophytes were isolated from cucumber roots and then screened on Waito-C rice, in order to identify plant growth promoting
fungal strains. The fungal isolate GAH7 provided the maximum shoot length (11.3cm) in comparison to control treatment (7.8cm).
In a separate experiment, bioassay of GAH7 significantly promoted growth attributes of cucumber. The GAH7 culture filtrate
(CF) was found to contain physiologically active gibberellins in higher concentrations (GA1, 0.81ng/ml; GA3, 4.34ng/ml and GA4, 9.31ng/ml) in conjunction with physiologically inactive GA9 (0.74ng/ml), GA15 (0.97ng/ml), GA19 (1.67ng/ml) and GA20 (0.46ng/ml). Isolate GAH7 produced higher amounts of GA3, GA4, GA9 and GA19 than wild type Fusarium fujikuroi, which was used as control for GA production. Gibberellins were analyzed through gas chromatograph/mass spectrometer (GC/MS)
with selected ion monitoring (SIM). The fungal isolate GAH7 was later identified as a new strain of Phoma on the basis of sequence homology (99%) and phylogenetic analysis of 18S rDNA sequence.
Phoma sp.-Gibberellins-Endophytic fungi-Cucumber-Growth promotion
Full-text Article · May 2009 · World Journal of Microbiology and Biotechnology
[Show abstract][Hide abstract]ABSTRACT: Endophytic fungi are plant symbionts that produce a variety of beneficial metabolites for plant growth and protection against
herbivory and pathogens. Fourteen fungal samples were isolated from the roots of soybean cultivar Daemangkong and screened
on waito-c rice for their plant growth-promoting capacity. Twelve of the fungal isolates promoted plant growth, while two
inhibited it. The fungal isolate DK-1-1 induced maximum plant growth in both waito-c rice and soybean. The plant growth promotion
capacity of DK-1-1 was higher than the wild type Gibberella fujikuroi. Gibberellin (GA) analysis of culture filtrate of DK-1-1 showed the presence of higher amounts of bioactive GA3, GA4, and GA7 (6.62, 2.1 and 1.26ng/mL, respectively) along with physiologically inactive GA5, GA15, GA19, and GA24. Phylogenetic analysis of 18S rDNA sequence identified the fungal isolate as a new strain of Cladosporium sphaerospermum. Gibberellin production and plant growth-promoting ability of genus Cladosporium are reported for the first time in the present study.
Article · Apr 2009 · World Journal of Microbiology and Biotechnology
[Show abstract][Hide abstract]ABSTRACT: Seed dormancy behavior of weed seeds is a critical determinant of their survival rates in a given cropping system as it helps the weeds to evade herbicides and other weeding practices. We investigated the effects of red light, alternating temperature, stratification duration and different doses of nitrogen containing compounds alone or in combination with red light on breaking seed dormancy of Chenopodium album L. The application of red light (80 μmols-1m-2) significantly increased seed germination of C. album in all treatments. Germination
rates of 12 h incubated seeds were highest under 20 min of red light irradiation than 1 min, 5 min and 10 min treated seeds. Germination rate was significantly higher at alternating temperatures of 25°C and 5°C for 12 h each with an irradiation of red light (80 μmols-1 m-2) for 10 min than other treatments. Stratification period of 15 days significantly stimulated germination percentage of seeds incubated in dark, although 5 days of stratification along with red light application for 10 minutes exhibit similar effects on seeds. Seed germination was also enhanced by nitrogen containing compounds like NaNO2, KNO3, NH4Cl and NH4NO3. We observed that seed germination increased significantly with 25 mM KNO3 and 10 mM NH4NO3 in dark condition, while NaNO2 and NH4Cl enhanced seed germination under red light irradiation. It was concluded that red light alone or synergized with alternating temperatures, stratification and nitrogen compounds, especially nitrite and ammonium enhanced seed germination of C. album. Thus, the red light can play a vital role in present and future weed management strategies.