فصلنامه زیست شناسی گیاهی ایران
سال سیزدهم شماره 3 (پیاپی 49، پاییز 1400)

Water limitation is the most severe stress factor limiting plant growth and crop production in arid and semi-arid regions. Several strategies have been developed in order to decrease water limitation effects caused by the rainfed condition on plant growth. Among them, the use of putrescine and bio-fertilizers such as plant growth promoting rhizobacteria (PGPR) and Mycorrhiza play a significant role in yield improvement. Therefore, to study biofertilizers and putrescine’s effect on biomass and some physiological and biochemical traits of vetch (Vicia villosa) under rainfed conditions, a factorial experiment was conducted based on a randomized complete block design with three replications in a research farm at the University of Mohaghegh Ardabili in 2019. Experimental factors included biofertilizers (no biofertilizer as control, application of Rhizobium, Mycorrhiza, combined application of Mycorrhiza and Rhizobium, Rhizobium and Azotobacter, Mycorrhiza and Azotobacter, Rhizobium with Mycorrhiza and Azotobacter) and foliar application of putrescine in three levels (water as control, 0.5 and 1mM putrescine). The results showed that both application of Azotobacter with Mycorrhiza and Rhizobium and foliar application of 1 mM putrescine increased catalase, peroxidase and polyphenol oxidase enzymes activity )37.08, 37.54 and 34.41% respectively (, maximum fluorescence and anthocyanin content )56.94 and 4.57% respectively( compared to no application of biofertilizers and foliar application of putrescine. Also, both application of Azotobacter with Mycorrhiza and Rhizobium and foliar application of 1 mM putrescine increased total biomass by about 56.9% compared to no application of biofertilizer and putrescine. It seems that the application of biofertilizers and putrescine can increase the total biomass of Vica villosa under rainfed conditions due to improving the physiological and biochemical traits.

Salicylic acid (SA) is known as an influential signal molecule in plant responses to environmental stresses. In this study, the effects of SA as a pre-treatment of psyllium (Plantago ovata) seeds on seedling growth, photosynthetic pigments, proteins and amino acids, and accumulation of soluble sugars and starch in response to salinity stress were investigated. Psyllium seeds were soaked with 0 and 500 μM SA for 24 h and sown in the research greenhouse of Iranshahr University in 2019, and the seedlings were exposed as a factorial design to 0, 25, 50, 100, 150 and 300 mM NaCl at 3-day intervals for 20 days. The results showed the seedling growth rate, photosynthetic pigments including chlorophylls and carotenoids, protein concentration as well as accumulation of soluble sugars and starch were severely reduced due to salinity stress. However, the accumulation of free amino acids and proline increased in response to salt stress. SA treatment improved the length of the shoot, increased the amount of pigments, decreased the amount of amino acids, and caused the accumulation of proteins and proline. In addition, an increase in the amount of non-reducing sugars and starch, which was associated with no change or decrease in the concentration of reducing sugars at high salinity levels, occurred in response to SA. These results show that priming the seeds with SA before sowing can increase the plant tolerance to salinity stress through the accumulation of non-reducing sugars and proline and thus maintain the turgor pressure of cells.

Gaseous molecules hydrogen sulfide (H2S) and salicylic acid (SA) enhance plant acclimation to environmental stresses such as salt stress. In the current study, the effects of priming of alfalfa seeds with sodium hydrosulfide (NaHS) (0.75 mM) as H2S-donor or SA (0.75 mM) on the improvement of germination indicators and the growth of seedlings under salt stress (0, 25, 50 and 100 mM) and also the decline of oxidative damages caused by salt stress (0 and 50 mM) were evaluated. The results showed that under unprimed conditions, salt stress had negative effects on different indicators of alfalfa seed germination and also on the growth of alfalfa seedlings. In addition, under unprimed conditions, the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2) significantly increased under salt stress. NaHS-priming and SA-priming showed positive effects on germination indicators and root length significantly increased in the seedlings obtained from NaHS- or SA-primed seeds. NaHS-priming and SA-priming decreased the accumulation of MDA and H2O2 under salt stress conditions showing the effect of priming treatments in decreasing oxidative stress. In addition, in response to salt stress, NaHS-priming and SA-priming significantly increased the levels of total sugars (especially 1 and 3 days after germination), when compared with their levels under unprimed conditions. Therefore, NaHS-priming and SA-priming treatments enhance plant responses in the first days after germination against salinity by reducing oxidative damages through activation of the antioxidant defense systems.

Phalaenopsis (the moth orchid; Phalaenopsis spp.) is currently the most sold indoor potted crop in the world’s major floriculture markets. The effects of light quality in night interruption (NI) and NPK fertilizers were examined on the vegetative growth and flowering of Phalaenopsis, an Evolution cultivar, in a factorial experiment as a completely randomized design. Young 6-old months plants from the last days of August to October when the length of flower buds was about 5 cm, were grown under ambient light/dark of greenhouse (control), ambient light plus night interruption (23:00–03:00 h) with light intensity at 20 µmol m−2 s−1 with three spectra light including white (400-700 nm), blue (450 nm) and red (680 nm) LED lights. Also, three water-soluble NPK fertilizers including 19N-6P-20k, 12N-12P-36K and 20N-20P-20K were applied to plants at concentrations of 1/1000. The tallest plants (25 cm) at flowering were in the control group in the 20N-20P-20K fertilizer treatment. NI with white LED + 19N-6P-20k or control + 20N-20P-20K effectively increased floret number. To obtain early flowering using 12N-12P-36K (without NI) and NI treatment with white light + 20N-20P-20K and blue light + 12N-12P-36K during their reproductive stage could be suggested. Plants fertigated with 12N-12P-36K and NI with red LED, showed the highest amount of chlorophyll a (0.36 mg/FW) and b (0.17 mg/FW). The highest amount of K and P in all three light treatments were obtained in 12N-12P-36K fertilizer. The experimental results suggested that NI treatment can be used effectively to promote flower induction with an increased growth rate. To obtain high-quality plants, however, NI with red and white LEDs should be considered.

Measurement of diversity indices and the local vegetation study are often suitable tools for studying the status of forests and rangelands and evaluating them. The purpose of this study is to evaluate the trend of vegetation changes in the dust center of Khuzestan province. In this study, the effect of rainfall fluctuations and irrigation of seedlings cultivated in the region on the percentage of cover and the type of native species during four consecutive years and in two seasons in the Hanitiah region was investigated. For this purpose, 5 transects with a length of 100 meters with 50-meter intervals were constructed in a systematic random manner in the study area. A total of 30 fixed plots were installed along transects. In two growing seasons, spring and autumn, from 2017 to 2020, the type and percentage of coverage of native species were recorded. Indices of dominance, uniformity, and species diversity of Simpson and Shannon were measured using PAST software. The results of one-way analysis of variance (ANOVA) showed that there is a significant difference between the mean of dominance, Shannon and Simpson indices, percentage of cover, and the number of species in the spring of different harvest years. But in comparing Shannon and Simpson indices and summer coverage, there is no significant difference between July 2019 and 2018. The species in the plots were all short-lived and the measured variability was time-dependent. From the above observations and results from the Hanitiah region, it can be concluded that despite the return of many short-lived species following the irrigation of cultivated seedlings and recent rains, the area is still very sensitive and fragile. Therefore, for complete revival, it still needs complete management, planning, and exclusion.

Mamoulan drop waterfall is located vicinity of the Kashkan river in the south of Lorestan province. The presence of a river and the waterfall consequently special vegetation of wetland species have been created in the area. The plant species Primrose (Primula gaubaeana Bornm.), Maidenhair (Adiantum capilus-veneris L.) and Sow thistle (Sonchus maritimus L.) are species that grow in the area due to high humidity and constant water flow. Primrose is a beautiful plant, Sow thistle a plant with high biomass used for livestock and Maidenhair as a plant medicine are among the more important plant in this habitat. According to the results; 138 plant species were identified that belonged to 110 genera and 55 plant families. There are 36 species of wetland plants (26.1%) in the region. According to the habitat and type of life, 26 species (18.84%) are Hygrophyte plants, 9 species (5.8%) are Helophytes and Hydrophyte 1 species (0.72%). Fabaceae (20 species), Asteraceae (13 species) and Brassicaceae (8 species), plant families had the highest number of species and the share of species richness in the study area. Therophytes (40.58%), Hemicryptophytes (36.23%), Phanrophytes (11.59%) and Geophytes (10.14%), are major biodiversity of plant species in the region included. Plant species of the region include: 40 species unique to the Iranian-Turanian vegetation region (29.4%), 23 species belonging to the Iranian-Turanian, Mediterranean, European-Siberian region (16.9%) and 22 species from the region Iranian-Turanian, Mediterranean (16.7%) had the highest geographical distribution in the region. The conservation status of the Primula gaubaeana Bornm. based on the IUCN criteria of this species is considered as endangered (EN/Endangered).