Journal of Plant Physiology and Breeding
Volume:8 Issue: 1, Winter-Spring 2018

Cut roses are always valued for their beautiful and outstanding flowers. Apart from the physiological and nutritional features of the plants, there are many other factors which influence the marketable quality of cut roses over the entire period of production phase. Among them we tried to understand how plant age and different methods of stem treatment can modify cut stem physical properties. To do this, the effect of newly stented plants beside the three-year old stented plants combined with four stem training methods were evaluated for their cut flower qualities. The results showed that the time to bud break was shorter (seven days) for young plants while it reached to about 15 days in old plants particularly for the third and fifth buds. In general, young plants performed better for some quality traits such as higher stem length and higher flower and stem diameter. When shoots were bent over the fifth bud, the highest shoot weight and leaf area were produced in the new growing cut flowers. It was concluded that young plants tended to increase their foliage volume by producing more leaves on relatively vigorous shoots, thereby they increased their marketable stem quality.

In order to investigate changes in sodium ion (Na+), potassium ion (K+), dry matter mobilization and grain filling period of wheat (Triticum aestivum L.) under salinity stress, a factorial experiment was conducted based on randomized complete block design with three replications. Factors were salinity at four levels [no-salt (S0) and salinity of 25 (S1), 50 (S2) and 75 (S3) mM NaCl, equivalent of 2.3, 4.61 and 6.92 dS m−1, respectively] and four cycocel levels [without cycocel (C0) and application of 400 (C1), 800 (C2) and 1200 (C3) mg L-1 cycocel)]. Results showed that salinity stress decreased grain yield, chlorophyll index, grain filling period, stomata conductance and relative water content in plant shoots. But grain filling rate and dry matter remobilization from shoots increased. Application of cycocel at C3 level led to the reduction of 36.36% and 5.75% in dry matter remobilization from shoot and stem, respectively. In the case of mineral content, Na+/K+ ratio was increased with increasing salinity level. At all salinity levels, cycocel application resulted in lower Na+ content and Na+/K+ ratio. Higher K+ accumulation in the cycocel treated plants, resulted in a low Na+/K+ ratio leading to their efficiency in salinity tolerance. It was concluded that cycocel can be a proper toolfor increasing wheat yield under salinity condition.

In order to investigate the effect of priming and UV stress on pea (Pisum sativum L. cv. Dorian), a pot experiment was conducted as factorial based on completely randomized design with 22 treatments (11 type of seed priming and 2 UV stress conditions) and four replications at Razi University during 2014. The results showed that the impact of seed pre-treatment was significant on all traits studied. Also, effect of UV stress was significant on relative water content (RWC), maximum quantum yield of PSII, total chlorophyll (Chl total) content and hydrogen peroxide concentration (H2O2). Interaction between seed priming and UV stress was also significant (p≤ 0.01) for RWC, Chl total content and H2O2 concentration. Generally, the results indicated that UV stress has harmful effect on the pea plants. On the other hand, hydro-priming (HP) had a better effect on the morphological characteristics (stem length and fresh weight) and RWC, especially, under non-UV stress condition. But, HP for 12 h + UV-AB for 2 h and also HP for 11 h + UV-AB for 3 h showed the lowest Chl total content, maximum quantum yield of PSII, stem length and fresh weight of plant and also had the highest concentration of H2O2. Therefore, these two pre-treatments have a negative impact on the pea plant and their use is not recommended for the pre-treatment of seeds in pea.

In order to investigate the effect of water treatment and nitrogen fertilizer application on remobilization and grain yield of bread wheat cultivars, an experiment was carried out as split-split plot design based on randomized complete blocks with three replications. Three levels of irrigation (full irrigation, withholding irrigation at heading, withholding irrigation at anthesis) were assigned to main plots, different times of nitrogen fertilizer application (application of 120 kg/ha nitrogen in four different times: 20 kg at sowing + 100 kg/ha at tillering, 20 kg at sowing + 100 kg/ha at bolting, 20 kg at sowing + 50 kg at tillering + 50 kg at bolting, 20 kg at sowing + 50 kg at tillering + 50 kg at heading) were randomized in sub-plots and five bread wheat cultivars (Zarrin, Pishgam, Urum, Zare, Mihan) were assigned to sub-sub-plots. Withholding irrigation at different developmental stages of wheat increased remobilization percentage of all cultivars. However, application of nitrogen at the heading stage reduced remobilization. The highest and lowest remobilization were recorded for Urum and Zarrin with 62.13% and 20.33%, respectively. Grain yield was significantly reduced with the reduction of water availability. Mean grain yield of all cultivars was 7.500 ton/ha under full irrigation, which reduced to 6.500 ton/ha when irrigation was withheld. Nitrogen fertilizer applicationimproved the grain yield of wheat cultivars. The highest grain yield was obtained for Mihan by 9.39 ton/ha under full irrigation and nitrogen application at sowing + tillering + heading. The higher grain yield of tolerant cultivars under water deficit treatments was attributed to remobilization of unstructured carbohydrates from shoot to grain. It seems that selection of cultivars with higher translocation of dry matter and contribution of pre-anthesis assimilates in grain filling under water stress, can be a suitable strategy to produce high yielding cultivars under water deficit stress condition.

Nowadays, the use of chlorophyll a fluorescence has become a simple and nondestructive method for detecting plant’s photosynthetic response to different kinds of stress. The aim of this research was to evaluate the effects of different concentrations of clodinafop-propagrgyl (TOPIK®) herbicide on some chlorophyll a fluorescence parameters of different corn cultivars (SC260, SC400, SC704) in response to salicylic acid (SA) application (control, seed priming, spraying on plants three days before herbicide treatment, concurrent with herbicide application) in greenhouse of University of Tabriz in 2017, using a factorial arrangement of treatments based on randomized complete block design with three replicates. Results showed that by increasing of TOPIK levels in the absence of SA, the maximum fluorescence (Fm), variable fluorescence (Fv), efficiency and/or activity of water-splitting complex at donor side of photosystem II (Fv/F0) and maximum photochemical efficiency of photosystem II (Fv/Fm) decreased but minimum fluorescence (F0) increased. However, application of SA improved several parameters of chlorophyll a fluorescence in some corn cultivars. Application of SA as seed priming and spraying on plants three days before TOPIK treatment had higher effect on the studied cultivars than SA spraying concurrent with herbicide application. Correlation between the F0 and Fv/F0 was significant and negative. Also shoot dry weight (SDW) taken at 28 days after herbicide application had significant and positive relationship with Fv/Fm taken at 7 days after herbicide application. The findings of this research demonstrates that chlorophyll a fluorescence parameters and especially Fv/Fm are fast and reliable criteria for determining the effects of herbicides, such as TOPIK, and/or plants growth regulators, such as salicylic acid, shortly after treatment as compared to classical methods.

This study was conducted to determine the effect of drought stress on yield and some physiological characteristics of wheat cultivars. Six cultivars were grown under normal and drought stress in greenhouses and field conditions. Leaf samples were taken for physiological measurement including relative water content, transpiration rate, membrane stability, chlorophyll content and chlorophyll fluorescence parameters and stomatal frequency and length. Grain yield was determined for plants grown under field condition. Results showed that treatments have a significant impact on plant traits. Drought stress decreased leaf chlorophyll content and photochemical efficiency of PSII due to increasing F0 and decreasing Fm and increased ion leakage. Drought stress also decreased grain yield and the highest yield was obtained in plots with normal condition. Cultivars Alvand and Chamran showed the highest level of photochemical efficiency of PSII, membrane stability and grain yield under drought stress and were considered as the more tolerant cultivars to drought stress than other cultivars under conditions of this investigation.

Effect of magnetic fields (MFs) and silver nanoparticles (SNPs) on a biological organism vary depending on their system and applied materials, time and intensity. In recent years, many studies have been conducted on the sensitivity of living organisms to MFs and NPs. For this purpose, an experiment was carried out in 2016 to study the effects of MF and SNPs on marigold (Calendula officinalis L.) using randomized complete block design with four treatments and three replications. The treatments were as follows: control, MF with B=3 mT for an hour per day, SNPs (50 ppm) and combination of MF (B=3 mT) and SNPs (50 ppm). Results showed that phenolic content, DPPH radical scavenging, phenylalanine ammonia lyase, polyphenoloxidase, catalase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase activity were significantly increased by the application of MFs and SNPs as compared to the control group. It seems that the MF+SNPs treatment had the best effect on the antioxidant status of C. officinalis L. and may be suitable alternative for chemical compounds used in agriculture.

We studied the effect of polyethylene glycol (PEG)-induced osmotic stress on pear cultivars (Harrow Sweet and Bartlett) under in-vitro culture conditions. Explants were cultured in QL medium containing 4% and 8% PEG6000 using a factorial experiment based on completely randomized design. The medium without PEG was considered as control. Drought injury index, which was calculated based on morphological disorders, increased at 8% PEG nearly to 2.00 and 1.50 units in CVs. Bartlett and Harrow Sweet, respectively. Owing to osmotic stress, the increase of malondialdehyde was accompanied with the reduction of cell membrane stability index in both cultivars. Total phenolic components and antioxidant activity in leaves increased significantly in response to application of 4% and 8% PEG. However, the severity of increase was higher in CV. Harrow Sweet. It was revealed that CV. Harrow Sweet had higher tolerance to osmotic stress than Bartlett. Moreover, the parameters related to oxidative damages and ROS scavenging capacity were more descriminant against osmotic stress under in vitro system.

Peganum harmala L. is a shrub perennial plant of Zigophyllaceae. It is used for treatment of parkinson in folk medicine and has antitumor and antioxidant activity. This species is usually propagated by seeds but the span of seed viability is short. On the other hand, since this is a wild plant and is not cultivated, it is exposed to extinction due to overuse. In order to solve this problem and optimize secondary metabolite production in this plant, the first step is in-vitro optimization of callus induction and shoot regeneration. To achieve this goal, leaf, hypocotyl and embryo axis were cultured on MS medium containing different concentrations of 2,4-D (0, 0.25 and 0.5 mg L-1) in combination with BA (0, 0.5, 1 and 2 mg L-1). The results of analysis of variance showed that the main effects of hormones and explants and some interactions were significant on callus induction and shoot regeneration. Maximum callus induction and shoot regeneration was obtained in the medium supplemented with 0.5 mg L-1 2,4-D and 1 mg L-1 BA for the leaf and hypocotyl explants, respectively.

Genetic diversity among 64 rice genotypes including 56 M5 mutants and 8 check varieties was studied using multivariate analysis. The experimental materials were evaluated during growing season of 2013-14 at the experimental field of Rice Research Institute of Iran (RRII), Rasht, Iran. The field experiment was arranged in a randomized complete block design with three replications. With respect to the positive and significant partial regression coefficients and direct effects of number of panicles per plant and number of spikelet per panicle, it could be stated that increasing the amount of these traits will cause an increase in grain yield. The dendrogram from cluster analysis divided all 64 rice genotypes into three main groups. Maximum distance existed between clusters II and III, therefore the genotypes selected from these clusters could be used in hybridization programs. The first principal component included plant height, internode length, number of panicles per plant, panicle length, panicle weight, number of filled grains, grain productivity, 100 grain weight, grain width and grain yield. Second principal component included days to flowering, number of panicles per plant and number of unfilled grains. Two-dimensional plot based on the first two principal components indicated the existence of differences among rice genotypes under study. The presence of vast diversity among 64 rice genotypes by cluster analysis was also confirmed partly by the three-dimensional graph of three principal components. In conclusion, the studied genotypes represent a rich source of genetic diversity and could be useful in rice breeding programs. The crosses G53 × G39 and G62 × G11 will be useful for hybridization, because the parental genotypes were identified as being most divergent.