JOURNAL OF PLANT PHYSIOLOGY AND BREEDING
Year:2020 | Volume:10 | Issue:1|Papers Count:12

Polyploids are organisms that have more than two paired homologous sets of chromosomes. Polyploidy has played a significant role in the evolution and diversification of higher plants. Artificial polyploidization has been induced using a few antimitotic chemicals such as colchicine, trifluralin and oryzalin. The type of mitotic inhibitors and their concentration and duration time are variable and species-dependent. This technique can be applied ex vitro or in vitro of which, tissue culture is simpler and more efficient. Changes in nuclear DNA content, gene expression and developmental processes due to ploidy manipulation can lead to morphological, anatomical and physiological changes in polyploid plants. In general, polyploid plants exhibit larger organs, greater biomass, higher yield, superior tolerance to biotic and abiotic stresses as well as higher primary and secondary metabolites. Also, polyploidy often reduces fertility and allows the production of seedless fruits. In ornamental plants, increasing the size of polyploid flowers is aesthetically and economically important. There are two direct and indirect methods for the ploidy determination of plants. Indirect methods are simpler but more inaccurate, involving the relationship between ploidy level and morphological (i. e. plant height, leaf size and pollen diameter) and anatomical (i. e. stomatal frequency and size as well as chloroplast number in guard cells) properties. In contrast, direct assay methods, such as chromosome counting in mitotic cells of root-tips and flow cytometry are accurate techniques for the determination of ploidy level in plants. Overall, polyploidy manipulation has long been used in improving the yield of many crop plants and can be considered as one of the most promising tools in plant breeding programs.

Scarcity of water is a severe environmental constraint and the growth and development of tomato (Lycopersicon esculentum Mill. ) seedlings are strongly inhibited under drought stress. Putrescine (PUT) is involved in drought stress tolerance. There is little information about the exogenous application of PUT on tomato seedlings under drought stress. This experiment was carried out to examine the application of putrescine on some physiological and biochemical characteristics of tomatoes under water stress. Plants were exposed to three water conditions: 100% (ET0) as the nondrought treatment (or control), 75 and 50% of ET0 as the water-stress treatments. Foliar application of PUT was done using 0. 5 and 1 mgL-1 concentrations, while control plants were sprayed with distilled water. Drought stress significantly affected plant growth and productivity, and reduced leaf area (LA), plant height and fruit yield at 50% ET0 compared to the control treatment. Also antioxidant enzymes such as SOD, PPO and CAT were increased by increasing the drought stress level. Moreover, the activity of PPO, CAT and SOD enzymes were elevated by the PUT foliar application. Results showed that appropriate PUT doses persuade biosynthesis of important metabolites, which may reduce the negative effects of drought stress on tomato plants.

The present study aimed at evaluating the impact of drought stress combined with foliar application of ascorbic acid on grain yield and its components in sweet corn. The experiment was conducted as split plot design based on randomized complete block design with three replications at Agricultural Research Station of Ardabil in the 2016 growing season. The main plots were four levels of drought stress as irrigation after 70 (as control), 100, 130 and 160 mm evaporation from the class A pan, and the sub-plots were four levels of ascorbic acid (0 as control, 150, 200 and 250 ppm). The results revealed that drought stress significantly decreased the ear length, number of kernels per ear, number of kernel rows per ear, number of kernels per row, dry weight of husks, 300-kernel weight and grain yield. Although foliar application of ascorbic acid at some concentrations had positive effect on all traits of sweet corn, except dry weight of husks and ear length, but more results are needed to recommend its usefulness under drought stress conditions of this experiment.

Lead pollution is an important issue in the world. In this research, maize plants were treated with different concentrations of Pb (0, 0. 25, 0. 75, 1, 1. 5, 2. 5 and 5 mM) as lead (II) nitrate for 10 days. The results showed that an increase in lead concentration leads to a reduction in growth, chlorophyll a and b content and an increase in oxidative damages. Application of Pb caused a progressive increase of hydrogen peroxide content, which was followed by a significant level of lipid peroxidation. These changes were accompanied by an increase in nitric oxide content at the low and its reduction at the high concentrations of Pb. The small increase in the generation of hydrogen peroxide and nitric oxide are envisaged as messengers in signaling pathways that may act in triggering defense functions to detoxify lead. Therefore, plant stress tolerance variables, including proline, ascorbic acid, flavonoids and anthocyanins content and activity of antioxidant enzymes, enhanced under different lead applications.

The photosynthetic light phase of spiny cocklebur (Xanthium spinosum L. ) plant was studied by JIP-test at different times (12, 36, 60 and 84 hours) after the application of nicosulfuron ( ® Cruz) and bentazon ( ® Basagran) herbicides. Results indicated that the application of nicosulfuron did not affect most of the chlorophyll a fluorescence (ChlF) parameters. But, the application of bentazon significantly decreased PSII activity due to increasing F0 and decreasing Fm, Fv, Fv/F0 and especially Fv/Fm. The maximum effect of bentazon was observed on the donor side of PSII by increasing ABS/RC and decreasing TRo/RC and also by reduction of φ E0. Reduction in photosynthesis relative vitality (PI) of photosynthesis apparatus by bentazon affected photosystem II (PSII) reaction centers, Fv/Fm and φ E0. The highest negative effect of bentazon on PSII activity was recorded at 36 hours after herbicide application. Bentazon via increasing KP, decreased electron transportation.

To study the effects of methanol on some physiological and biochemical characteristics of pot marigold (Calendula officinalis L. ) under drought stress, a factorial experiment was conducted based on a randomized complete block design with three replications under greenhouse conditions in 2017. Factors included the foliar application of methanol at four levels [0 (control), 20%, 30% and 40%] and four irrigation treatments (irrigation at 40, 60, 80 and 100% of field capacity). Increasing water deficit, significantly reduced chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, Fv/Fm and stomatal conductance, whereas 20 and 30% methanol application significantly improved these traits. Irrespective of 40% methanol application, the moderate and severe water deficit treatments led to the decrease of chlorophyll a, total chlorophyll, carotenoid and Fv/Fm. Also, water deficit showed a significant increase in soluble sugars content, proline accumulation and CAT, POD and PPO activity. Compared with the non-methanol treatment, the application of methanol increased the above-mentioned characteristics. The maximum values of these variables were obtained with the application of 40% methanol under severe water limitation conditions. It was indicated that the improvement of biomass due to methanol spraying was associated with the increase of antioxidant defense abilities and maintaining many physiological processes in the stressed plants.

Tuberose is an important cut flower in Iran and throughout the world. Since nutrition is of crucial significance for the growth, development, and quality of ornamental plants, the present study aimed to explore the effect of different levels of humic and folic acids on yield and quantitative and qualitative traits of tuberose (Polianthes tuberosa L. ) based on a randomized complete block design with three replications in the Faculty of Agriculture, Agriculture and Natural Resources University of Gorgan, Iran in 2016. Humic and folic acids were applied at the rates of 0, 50, 100 or 150 mg L-1. The foliar application was performed in three phases, i. e. 30, 50 and 70 days after planting. The recorded traits included spike length, stem length and diameter, shoot fresh weight, floret number, leaf number and area, flower emergence time, bulblet number, root development depth, N, P and K content, vase life, and total chlorophyll. Analysis of variance showed that the application of humic acid significantly influenced all measured traits, except leaf number and flower emergence time. As the humic acid rate was increased to 150 mg L-1, leaf total chlorophyll content was increased by 52 percent showing a significant difference with control. The foliar application of humic and folic acids increased N, P and K contents of leaves, and the strongest effect was observed at the rate of 150 mg L-1. The results lead us to the conclusion that the application of 150 mg L-1 humic acid and folic acid had the strongest impact on increasing the quantitative and qualitative traits of tuberose.

Cold stress induces biochemical and physiological changes in plants. Therefore, it is important to identify and apply compounds that can increase plant tolerance to cold. Nowadays, the use of nanoparticles as a suitable solution to increase plant resistance to environmental stresses is considered. Besides, polyamines play an important role in regulating plant defense responses to environmental stresses. This study aimed to investigate the effects of spermine and titanium dioxide nanoparticles (TiO2 NPs) on physiological responses of licorice (Glycyrrhiza glabra L. ) plants to cold stress. Results showed that cold stress increased the content of total protein, phenolic compounds, glycine betaine, soluble sugars, glycyrrhizin, proline, hydrogen peroxide and malondialdehyde and also the activity of antioxidant enzymes, but decreased photosynthetic pigments content and growth indices. Spermine increased most of the features measured at low temperature but decreased the content of hydrogen peroxide and malondialdehyde. The production of glycyrrhizin was stimulated by cold stress and also by the application of spermine and TiO2 NPs. The use of TiO2 NPs and spermine alleviated the negative effects of cold stress and improved licorice plant responses.

Optimization of medium components in in vitro cultures is very difficult because of having multifactor nature. To optimize the plant growth regulator concentrations (BA, IBA, GA3) for shoot proliferation of apple cv. 'Abbasi' a threefactor experiment was designed and performed in 20 points (20 treatments) using Design Expert software based on the response surface method. A completely randomized design using eight auxin combinations (IBA+NAA) was also carried out for in vitro rooting of microcuttings. Proliferated shoot number was linearly and positively affected by the BA factor, while the response of the leaf number was linearly and negatively affected by BA. The effect of GA3 on proliferated shoot length was negative and linear. The abnormal shoot percentage in a quadratic model was influenced by all three types of PGRs, i. e. BA, IBA and GA3; positively and linear by BA, positively and quadratic by IBA and negatively and quadratic by GA3. According to the results of this experiment, the optimum concentrations for BA, IBA and GA3 combination were 1. 5, 0. 1 and 0. 02 mg L-1, respectively, which resulted in the proliferated shoots with a rate of 2. 5 shoots per explant, with 0. 9 cm in length, 4. 3 leaves per shoot and 4% abnormal shoots. The percentage of shoot-tip necrosis was not affected by the evaluated factors. NAA was more effective than IBA for rooting microcutings. The medium supplemented by 1 mg L-1 IBA or 0. 5 mg L-1 NAA can be used successfully for rooting of apple cv. 'Abbasi' shoots in vitro.

Strawberry cultivation requires the use of cultivars adapted to the field or greenhouse conditions of the production region. Seven commercial short-day (SD) and day-neutral (DN) strawberry cultivars (Camarosa, Kurdistan, Mrak, Paros, Queen Elisa, Selva, Ventana) were compared using a completely randomized design for different morpho-physiological characters under greenhouse conditions. The cultivars showed variation for all of the studied traits. Days to flowering varied from 53. 2 to 94. 5 days among the cultivars and Paros followed by Camarosa required minimum days for flowering. The highest total chlorophyll content and fruit volume were obtained in Camarosa and Paros, while the highest fruit weight was found in Paros, Ventana, Camarosa and Kurdistan. The cultivar Camarosa produced the highest flower number (42. 0), fruit number (36. 3), fruit firmness (4. 8 N) and yield (424. 7 g per plant). The TSS/TA ratio was maximum in Paros and minimum in Ventana and Mrak. The highest fruit anthocyanin was recorded in Camarosa and Selva. Yield per plant had a positive correlation with total chlorophyll content of leaves, number of flower and fruit, weight and volume of fruit, while negatively correlated to leaf area and crown number. According to stepwise multiple regression analysis, yield had the highest positive relationship with the number of flowers and fruit weight, respectively. Generally, vegetative traits, as well as days to flowering and fruiting, were higher in the DN cultivars (Mrak, Selva). However, the SD cultivars produced higher flower numbers, fruit size and yield than the DN cultivars. The cultivars Camarosa and Paros were most adapted to the greenhouse conditions among the experimental cultivars.

This research was carried out using seven generations of MO17 (the paternal line), B73 (the maternal line), F1 (SC704), F2, F3, BC1 and BC2 to study the inheritance of chlorophyll fluorescence parameters and relative water content using generation mean analysis. The experiment was conducted in the research station of the University of Tabriz, Iran, with two replications for each generation under normal irrigation and two water deficit conditions. The existence of epistatic gene interaction was observed in controlling of F0, Fm, FV (in the severe stress condition), FV/Fm (in the normal condition), FV/F0 (in the normal and severe stress conditions) and RWC (in the normal and moderate and severe stress conditions). Duplicate epistasis was observed for all studied traits under the normal and water deficit conditions except RWC in the severe stress condition. Therefore, exploiting non-additive gene action and delaying the selection to advanced generations for physiological traits in maize was suggested to adopt in the programs aimed at developing drought-tolerant lines and hybrids.

Five varieties of Phalaenopsis (Nottingham, Dubrovnik, Andorra, Memphis, Bucharest) were self-pollinated and crossed with each either as the male or the female parents. The five self-pollination and 20 cross-pollination states were evaluated for six phenological and morphological characteristics. Pollination was performed using an orchid pollination syringe in a greenhouse with a temperature of 20-27 ◦ C, the humidity of 80% and light of 2500 lx during the 2018-2019 growing season. Nottingham under self-pollination conditions was better than other varieties and was superior to all crosses for all traits under investigation. The differences among males, females and their crosses were significant for all traits, except the time to the first pollination signs in which the effect of the female factor was not significant. In general, Nottingham was the superior variety in almost all traits and Dubrovnik was the worst variety in most traits either as male or female parents. Cross-pollination also had different outcomes in different traits. For example, for the time until swelling of the capsule, crosses Memphis × Nottingham and Nottingham × Memphis caused the capsule to fill later than the Nottingham parent. The cross Dubrovnik × Nottingham caused the capsule to fill earlier than the Dubrovnik parent. In the Dubrovnik × Nottingham cross, the weight of seeds per capsule, as an important trait, was higher than the Dubrovnik parent under self-fertilization conditions. Also, the cross-pollination was not suitable for increasing the weight of seeds per capsule in the Nottingham × Andorra cross. As an example for the capsule length, the Nottingham × Bucharest cross had smaller capsules than the self-pollination conditions of Nottingham and Bucharest. Therefore, depending on the importance of the traits under consideration in commercial production, cross-pollination can be used as a method, in addition to producing flowers with colors and shapes different from the parents, for improving the desired traits relative to one parent or both parents in self-pollination conditions.