Iranian Journal of Plant Physiology
Volume:10 Issue: 2, Winter 2020

Nitrogen is essential for both vegetative and generative stages of plant growth. Nitrogen efficiency is related to plant growth, production cost, and fertilizer residue. Azolla has the ability to increase nitrogen fixation from the atmosphere. Thus, Azolla cultivation in paddy field is one strategy for improving nitrogen fertilizer efficiency and increasing plant vegetative and generative growth. The objective of this study was to evaluate the role of Azolla on improving nitrogen efficiency. This study was conducted from January to April 2018 in irrigated paddy field of Lubuklinggau Selatan II, Lubuklinggau. The study was laid out in a randomized block design arrangement with 4 replications. Treatments were combinations of Azolla and urea which were applied during vegetative and generative stages: 115 kg N ha-1 without Azolla (K1), 115 kg N ha-1 + 1000 kg ha-1 Azolla (K2), 86 kg N ha -1+ 1000 kg ha-1 Azolla (K3), 58 kg N ha -1 + 1000 kg ha-1 Azolla (K4), 29 kg N ha-1  + 1000 kg ha-1Azolla (K5), and zero N+1000 kg ha-1 azolla (K6). The application of 86 kg N ha-1 and 1000 azolla kg ha-1 (K3) increased 15.54% rice growth, 25.49% yield, and improved the N fertilizer agronomic efficiency (AE), agro-physiological efficiency (APE), utilization efficiency (UE), and N efficiency ratio (NER).

Salicylic acid (SA) is a phenolic compound and its foliar application shows regulatory effects on plants. In this research, Ajowan (Carum copticum) plants were treated with 0, 0.5, and 1 mM SA and proline, total phenol, chlorophylls, carotenoids, soluble sugar, N, P, and K contents were studied. Results showed that application of SA affected both quantitative and qualitative traits of Ajowan. The plants treated with SA (0.5 and 1 mM) showed higher plant height, number of umbels per plant, stem diameter, number of branch, number of seed per umbel, seed yield, a thousand kernel weight, and percentage and yield of essential oil compared to control plants. With supplementation of SA and increasing its concentration, total phenol, chlorophylls, carotenoids, and soluble sugar contents were also significantly enhanced. Results also indicated that application of SA significantly improved the amount of macro-element (N, P, and K) in Ajowan compared to untreated plants. In sum, application of SA as a foliar agent resulted in a remarkable change in morpho-physiological and biochemical traits of Ajowan plants.

A protocol was developed for high frequency in vitro multiplication of an ornamental orchid, Phalaenopsis amabilis (L.) Blume var. Jawa, using plant growth regulators (PGRs). Protocorm-like bodies (PLBs), as explants were cultured on Murashige and Skoog (MS) medium fortified with various concentrations of kinetin (KIN) and indole-3-butyric acid (IBA), either individually or in combination. A combination of 1.00 mg l-1 KIN + 1.00 mg l-1 IBA was found to be suitable for regeneration of most measured characteristics especially maximum PLBs regeneration (30.40/plantlet), leaf number (5.93/plantlet), and root number (8.36/plantlet) from protocorm explants. The maximum number of plantlets (11.66) was calculated on MS medium supplemented with 1.00 mg l-1 KIN + 0.50 mg l-1 IBA, followed by 1.00 mg l-1 KIN + 1.00 mg l-1 IBA (10.33). Plantlets were transplanted to pots filled with cocochips and sphagnum moss (70:30) for acclimatization and transferred to the greenhouse. Upon ex vitro transfer, 90% of plants survived.

Melissa officinalis is a plant of Lamiaceae family with medicinal properties which is important for its aromatic, synthetic, and secondary metabolites. The aim of this research was to study the effect of selenium on secondary metabolites and antioxidant properties of Melissa officinalis. For this purpose, an experiment was done in a completely randomized design with four replications. The plants were treated with selenium (0, 0.2., and 5 µM). The experimental factors included root and shoot fresh and dry weights, protein contents, ascorbic acid, enzymes (catalase, ascorbate peroxidase, and superoxide dismutase), peroxide hydrogen, caryophyllene, and caryophyllene oxide. Results showed that application of selenium had positive effects on the wet weight of shoots and roots, dried weight of roots, and ascorbic acid, protein, enzyme (catalase, ascorbate peroxidase), peroxide hydrogen, caryophyllene, and caryophyllene oxide contents of the plants under study (p≤0.05). Also, high concentration of selenium (5 µM) lead to increased z-citral, citral, and geranyl acetate contents of Melissa officinalis essential oils while caryophyllene oxide content increased as a result of low concentration (0.2 µM). Therefore, application of selenium is concluded to play an effective role in increasing secondary metabolites in Melissa officinalis. In general, the study suggests that low concentration of selenium increases the growth of Melissa officinalis plants and improves their growth factors and morphology.

Current studies elucidate the metal stress attenuation potential of melatonin in Cucumis sativus seedlings growing in cadmium contaminated conditions. Melatonin is an indoleamine molecule, capable of ameliorating environmental stresses and regulate plant growth. Seeds of C. sativus were immersed in different levels of melatonin and grown under cadmium stress for 15 days. Cadmium stress reduced seed germination, growth, biomass production, gas exchange capacity, stomatal conductance and chlorophyll (Chl) content in C. sativus seedlings. The increased level of malondialdehyde (MDA) and hydrogen peroxide (H2O2) caused oxidative stress in C. sativus plants under cadmium stress. Melatonin application emphatically revamped germination, shoot, and plant biomass production. The melatonin pretreatment aggrandized plant length, root length, and expression of stress related genes (CsHA2, CsHA3, CsHA4, CsHA8 and CsHA9) along with amplification in activity of superoxide dismutase (SOD), nitrate reductase (NR), and ascorbate peroxidase (AP) helping in modulation of cadmium stress in C. sativus seedlings. The improved activity of antioxidant scavengerswas ascribed to the reduced level of H2O2 and MDA in plants under stress. Furthermore, conjugated increase of photosynthetic activity, indole acetic acid contents, and glutathione contents was observed in melatonin treated seedlings in a dose-responsive manner. The present study elicits the metal stress attenuating potential of melatonin by regulating metabolic activities and growth of C. sativus under cadmium stress.

Among abiotic stresses, drought is considered as the most important growth limiting factor, especially in arid and semiarid regions. Drought impacts can be adjusted by soil microorganisms. Accordingly, the present study was organized in order to the increase the tolerance of lemongrass (Cymbopogon citratus)to drought using plant growth promoting rhizobacteria (PGPR). Treatments were water stress in four levels (100% field capacity (FC), 75% FC, 50% FC, and 25% FC) and inoculation by PGPR in three levels (uninoculated, inoculated with pseudomonas sp., andinoculated with Azotobacter sp.). Water stress significantly decreased chlorophyll content.Compared to control, severe stress decreased Chlorophylle a+b by 36%. The maximum proline content was accumulated in plants under severe stress and PGPR application. Catalase (CAT) and super oxide dismutase (SOD) activities were increased by 77% and 71%, respectively under severe stress compared to the well-watered condition. The highest total phenol content (TPC) was obtained in the interaction of 50% FC and PGPR application. Moreover, 50% FC induced the maximum total flavonoid content (TFC) by 42% compared to 100% FC. Pseudomonas and Azotobacter increased the TFC by 6% and 18%, respectively in comparison with uninoculated plants. Essential oil (EO) content and yield were increased under 75% FC, and decreased under 50% and 25% FC. EO percentage in 75% FC and PGPR application was higher than other treatments. Under 75% FC, 14% increase in EO yield was reported for both Pseudomonas and Azotobacter application. To sum up, PGPR can improve the plant growth and EO properties by increasing antioxidant capacity of lemongrass.

Groundnut seed priming was performed with an aqueous solution of gibberellic acid (GA3) (0, 50, 100, and 150 ppm for 18h) and accelerated aging (96 h) was done prior to drought stress (-0.4, -0.6, and -0.8 MPa), then recovered. Investigated traits were germination percentage, mean germination time, germination rate, vigor index, plumule length, radicle length, seedling length, malondialdehyde content, antioxidant enzymes activities (CAT, SOD, and APX), soluble sugars, and protein content. In comparison with the control group, hormonal priming mitigated the negative effects of both aging and drought stress significantly. When seeds were recovered, hormonal priming was more effective. The obtained results showed that seed priming with GA3 performed after the accelerated aging had more pronounced effect on all parameters of recovered seeds. Hence, priming with 100 ppm of GA3 is suggested.

Raspberries composed of various varieties, are popular ingredients of daily diet with highly distinguished biological activities. In this study, a comparative investigation was conducted on various chemical potential of methanol extracts from Rubus loganobaccus L. leaf parts cultured in greenhouse and open-field. Biochemical activity of the extracts obtained from the field cultured leaves were observed to be higher than greenhouse cultured plants. In the antioxidant 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the field cultured leaves were better succeeded in radical scavenging with IC50 as low as 1.08 ± 0.75 μg/mL while in reducing power assay, open-field plants against greenhouse plants had a higher EC50 (2.82 ± 0.70 and 2.41 ± 0.75 μg/mL, respectively). Considerable antibacterial and antifungal activity were observed in open-field plants and greenhouse plants in minimum inhibitory concentrations (MIC) and minimum bacterial concentration (MBC) tests with a similar pattern, in which the lowest MIC and MBC in open-field and greenhouse plants were 5 mg/mL and 20 mg/mL, respectively, against Bacillus cereus and pseudomonas aeruginosa. This experiment revealed that leaf parts of Rubus loganobaccus cultured in greenhouse and in field possess a number of biological properties including antioxidative and antimicrobial potentials with the superiority of the later source which indicates the criticality of using natural products to improve human health.