The role of plant growth promoting bacteria on arsenic removal: a review of existing perspectives

Phytobial remediation is an innovative tool that uses plants and microbes to mitigate Arsenic (As) contamination of the environment. Recently, plant growth-promoting bacteria (PGPB) that assists phytoremediation has been highly touted for both improving plant metal tolerance and promoting plant growth while achieving the goal of large-scale removal of As. This review focuses on the PGPB characteristics influencing plants and the mechanisms in which they function to overcome/lessen As-induced adversities. Several recent examples of mechanisms responsible for increasing the availability of As to plants and coping with As stresses facilitated by PGPB will be reviewed. Although drawbacks to phytoremediation have been reported, encouraging results have been developed with regular monitoring. Introducing PGPB-assisted phytoremediation of As in a field requires an assessment of the environmental effects of PGPB, especially with respect to the impacts on indigenous bacteria

Geographic variation in seed, leaf and seedling traits of wild almond (Amygdalus scoparia Spach.) in Fars province

Knowledge about geographic variation within the native range of forest tree species is the logical first step in genetic studies. Wild almond (Amygdalus scoparia Spach.) is a multi-purpose species with a widespread geographic distribution in most of the vegetation regions of Iran. In order to study the geographic variation of wild almond, nineteen biometric features of seed, leaf and seedling from seven natural population of this species in Fras province were measured. Significant differences were observed among the populations for all of the studied characteristics. Hundred seed weight, leaf area and number of stems showed maximum variation among the studied traits. Seed traits presented a significant positive correlation in terms of mean annual rainfall. Correlation analyses between biometric traits and geoclimatic factors indicated the existence of clinal variation in some seed, leaf and seedling traits. Seedling leaf morphometric (dimension) traits decreased gradually from north to south populations; while seedling height declines from east to west populations. That means the geographic variation of the plant at the seedling stages reveals a two- way variation with the latitude and longitude. Principal component analysis (PCA) and cluster analysis of data revealed four distinct groups of populations, and separated populations of high rainfall area form that of lower rainfall area. Results also revealed that A. scoparia uses adaptive strategies in response to water deficit

The evaluation of IAA-production ability in indigenous Azospirillum isolates and their growth promoting effects on sweet corn

It has been years that Azospirillum is known to promote plant growth. Phytohormone (especially Auxin) production has the most important role in increasing the yield of inoculated plants. According to this, 60 strains of this genus were isolated, identified, and purified. This ability was evaluated in both qualitative and quantitative assays using colorimetric method and the effects of superior isolate on sweet corn were measured. Results revealed that the abundance and probability of the bacteria isolation is low and 17%. About 31.2% and 100% of Azospirillum strains were capable of producing IAA in qualitative and quantitative methods respectively. In greenhouse experiment, bacteria treatments had significant effects on corn fresh weight, total dry weight, root dry weight and total nitrogen and phosphorus content of the plant. This was considered to be as the result of more lateral root formation which enhances nutrition uptake. In conclusion, the green house results in respect to in vitro achievements show that fortunately it can be claimed that bacteria of the genus Azospirillum can be used widely for not only strategic gramineous plants like: corn, wheat, barely etc. but also for other useful plants.\ud \ud Key words: Azospirillum, Auxin, qualitative and quantitative methods, sweet corn

Impacts of soil humidity and shade on growth and biomass allocation of wild pistachio (Pistacia atlantica Desf.) saplings

A study on the impacts of soil humidity and artificial shading on growth, biomass production and its allocation to different organs of wild pistachio (Pistacia atlantica Desf.)saplings was carried out in Alborz research station complex (Karaj, Iran). One year seedlings were treated by soil humidity (20, 50 and 100 percent of field capacity) and shading (100, 70 and 50 percent of full sunlight) factors in a split plot experiment based on a randomized complete block design from June to December 2014. Results showed significant impact of oil humidity on height, collar diameter, fresh and dry biomass of leaves and stem as well as on total fresh biomass. Shade significantly decreased height, root and total dry biomass and root to shoot fresh biomass ratio. Moreover, wild pistachio saplings with different soil humidity treatments show different responses to shade. In particular, shade significantly decreases height, fresh leaves biomass and R/S fresh biomass ratio for well-irrigated saplings and increases these parameters for saplings under drought stress. Response trends of different parameters under humidity × shade treatments showed that shade can reduce undesirable effects of drought stress on wild pistachio saplings

Shade role in facilitation drought stress symptoms on physiology of mount Atlas mastic (Pistacia atlantica Desf.) seedlings

This investigation was carried out in Albroz research station complex (Karaj, Iran) during 2014 summer. Mount Atlas mustic (Pistacia atlantica Desf.) seedlings were treated by drought (moderate, sever and without drought stress) and shading (low, moderate and without shade) factors in a split plot experiment based on a randomized complete block design. After one month, physiological characteristics of leaves including RWC, soluble sugars, proline and pigments content, catalase enzyme activity and ion leakage were studied. Drought stress caused severe decrease in RWC and a, b and total chlorophyll contents. In contrast, shade by ameliorating drought stress significantly increased these parameters. Drought induced tolerance mechanisms in saplings and increased proline and carotenoid content while shade decreased these parameters significantly as well as a to b chlorophyll ratio. Interaction of drought and shade was significant for a chlorophyll and catalase activity, suggested that, drought treatments showed different responses to shade. Overall, results revealed positive effect of shade on drought induced saplings