فصلنامه اکوفیزیولوژی گیاهان زراعی
پیاپی 36 (زمستان 1394)

In order to investigate drought tolerance indices of 14 maize hybrids to different levels of water deficit, a split-plot experiment was conducted in complete randomized block design with four replications at the Agricultural Research Station, University of Tabriz. The main plots consisted of three levels of irrigation regimes (control, mild and severe water deficit) and sub-plots of 14 corn hybrids. Drought tolerance indices were calculated for the grain yields produced. Under mild drought condition, hybrids like SC702, SC500 and K3647×K18 were tolerant based on tolerance index (TOL) and stress susceptibility index (SSI) indices while hybrid SC 500 was the most tolerance one. Based on stress tolerance index (STI), mean productivity (MP) and geometric mean productivity (GMP) indices under both mild and severe stress conditions hybrids K166×K18, SC500¡ K3647×K18 and SC400 were found to be the most tolerant to water deficit than others. The STI and GMP indices that had highest positive correlation with grain yield under both of these stress conditions. Thus these two indices were determined as the best indices for selection of tolerant hybrids. Cluster analysis based on these two indices classified hybrids into two groups under mild stress and in three groups under severe stress conditions. Biplot graphs for two main components based on principle components analysis (PCM) displayed that SC500 to be a tolerant maize hybrid in both mild and severe drought stress conditions with high yield performance. Also, hybrids SC700 and SC704 were low yielders under both control and stress conditions and thus were identified to be as sensitive hybrids.

To study the effect of mycorrhizal symbiosis and drought stress on marigold¡ a factorial experiment in a completely randomized design with three replications was conducted at the Plant Research Laboratory of Islamic Azad University¡ Neyshabur branch in 2014. The first factor consisted of application and non-application of mycorrhiza (Glomus intraradices) and the second factor consisted of drought stress with three levels (irrigation based on 100%¡ 75% and 50% of field capacity). The results showed that growth parameters like plant height¡ leaf number¡ leaf area¡ root¡ shoot dry/fresh weight¡ Chla and Chlb content were significantly decreased by drought stress in both mycorrhizal and non-mycorrhizal plants. However¡ inoculation of plants by mycorrhizal fungus increased growth parameters and photosynthetic pigments as compared with non-mycorrhizal ones. Traits like RWC¡ potassium and phosphorus in response to drought stress were decreased. Inoculation of plant roots with Mycorrhizal fungi increased significantly RWC¡ potassium and phosphorus content of the plants under drought conditions as compared with non-inoculated plants. The results also showed the mycorrhizal symbiosis by Glomus intraradices improved drought tolerance of marigold through enhancing the absorption of water and mineral ions.

To evaluate the effect of potassium humate (PH) on drought stress in potato cultivars (Kaizer, Agria and Satina) a split plot experiment based on randomized complete block design with 3 replications was performed. Main factor was irrigation regimes, 1- irrigation every 7 days without PH application, 2- irrigation every 7 days PH application, 3- irrigation every 10 days without PH application and 4- irrigation every 10 days PH application, in which 250 ml of PH diluted in 300L water and plants were sprayed in three stage of plant growth: full emergence, before and after tuber initiation. Results showed that increasing irrigation interval decreased stem number per plant from 3.5 to 2.5, days to flowering from 60 to less than 50 days, , and tuber yield from 45 to less than 35 ton.ha-1. Cultivar×irrigation interaction in all attributes were not significant. The highest tuber yield produced by Kaizer (55 t.ha-1) when plants were irrigated every 7 days irrigation PH application and lowest by Agria (20 t.ha-1) in 10 days irrigation interval without applying PH. Kaizer not only produced high yield but also produced higher yield in every 7 or 10 days irrigation without PH application: 50 and 20 ton.ha-1, respectively. It seems that Kaizer could be a proper choice to be planted in drought prone regions like Ardabil. Applying PH resulted in increasing yield from 25 to 50 t.ha-1 under water deficit condition.

To study the effects of mycorrhizal inoculation and salinity stress on the growth, yield and nutrient concentrations of cumin (Cuminum cyminum L.), an experiment was carried out as split plot in a completely randomized block design at Zabol University Research Farm in 2013. Treatments consisted of three salinity stresses: 1 (control), 5 and 10 dSm-1, was considered as the main treatments, and four levels of mycorrhizal inoculation (Glomus intraradices, G. etanicatum, G. hoi and non-inoculation as control) as the sub-treatments. The effects of salinity on all traits under study, except umbers per plant, were significant, and severe stress (10 dSm-1) reduced 100 seed weight, number of seeds per umbel, concentrations of phosphorus, calcium and magnesium in seeds by 17.71, 11.4, 14.95, 46.08, 13.60 %, respectively, as compared to the control. The numbers of seeds per umbel and phosphorus concentration in seed were highest in G. intraradices with 28.4 and 54.4%, respectively as compared to control and umbels per plant was also maximum (9.7) by using G. etanicatum. Mycorrhizal inoculation did not have significant effect on calcium and magnesium concentrations in seeds and 1000 seed weight. However mycorrhiza × salinity stress interaction was significant about concentration of sodium, potassium and sodium to potassium ratio (Na/K) in seeds, as well as seed yield and seed number per plant. Among the species of mycorrhiza, applied G. intraradices had better performance in severe salinity (10 dS-1) and increased seed yield and seed number per plant by 28.5 and 47.6%, respectively in comparision control. The results suggested that mycorrhizal inoculation improves water absorption by plant. Yield increases of plants under different salinity regimes dependent on their mycorrhizal inoculation.

Soil compaction is one of the most important limiting factor for normal crop growth, because it reduces absorption by the plant. Application of organic fertilizers in agricultural soils can reduce the detrimental effects of soil compaction on plant growth and also supply some nutrients to plant. Thus, a factorial experiment was carried out in a randomized complete block design with three replications and 14 treatments to evaluate the effects of organic fertilizers in mitigating soil compaction. The first factor in this study was the source and amount of organic fertilizer at seven levels (control, farmyard manure, sewage sludge compost and municipal solid waste compost and each of organic fertilizers at two levels of 15 and 30 g/kg of soil). The second factor was soil compaction at two levels (bulk density of 1.2 and 1.7 g/cm3). To perform this experiment, 10 kg of dry soil was poured into special PVC pots and then seeds of single cross 704 corn were planted. At the end of the growth period, the corn shoot was harvested and concentrations of phosphorus (P), potassium (K), sodium (Na), iron (Fe), zinc (Zn), manganese (Mn), cadmium (Cd) and lead (Pb) were determined by dry ashing method. The results showed that concentrations of Cd and Pb in the shoot, related to the different treatments, were negligible. Concentrations of P, K, Fe, Mn and Zn in the corn shoot were increased significantly by application of farmyard manure, sewage sludge compost and municipal solid waste compost at both levels of soil compaction. However, Na concentration of shoot did not change significantly. Soil compaction significantly reduced P, Fe, Mn and Zn concentrations of corn shoot, but it affected concentrations of Na and K significantly. Application of organic fertilizers and increasing their levels reduced the negative effects of soil compaction on nutrients uptake by corn plant. This study showed that to improve forage corn nutrition, application of 15 or 30 g of farmyard manure or sewage sludge compost or municipal solid waste compost per kg of soil can be recommended to similar compacted and non-compacted conditions.

This research was conducted to study the effects of chemical and bio fertilizers on forage yield of alfalfa in a factorial experiment by using a randomized complete block design with 3 replications in 2012-2013 in Arak, Iran. Treatments were chemical fertilizers in four levels (control, potassium, phosphorus and whole micronutrients) and biological fertilizers in four levels (control, soil potassium solublizing bacteria, nitrogen-fixing bacteria and soil phosphorus solublizing bacteria). The results showed that the highest yield of alfalfa, in the first cut, was 1.76 t/ha by the use of phosphorus solublizing bacteria and 1.57 t/ha by using soil potassium solublizing bacteria. Although in the second cut the differences between chemical fertilizer and their interaction with biological fertilizer was not significant, but application of biological fertilizers could affect alfalfa yield in the second cut significantly. Application of soil potassium solublizing bacteria increased forage yield of alfalfa from 1.74 to 2.48 t/ha. The results also revealed that dry forage yield of alfalfa in control treatment was 2.5 t/ha and it was increased to 3.7 t/ha by using phosphorus solubilizing bacteria which is 1.2 t/ha higher than control.

Proper nutrition of plant is one of the most important factors to improve both quality and quantiy of crop yields. Accordingly, the effect of different levels of zinc and nitrogen on leaf area index, yield and yield components of green beans investigated in the summer of 2012. The experiment used was a split plot in randomized complete block design with three replications in the Dezful. In this study, the main plots consisted of four nitrogen rates of urea (0, 30, 60 and 90 kgha-1), and sub plots of four levels of zinc sulfate (0, 10, 20 and 30 kg.ha-1). The results showed that application of 90 N kg.ha-1 increased leaf area index, plant dry matter, grain yield, biological yield, harvest index and protein content. Use of zinc sulfate at the rate of 20 kg.ha-1 was superior in grain yield and yield components. The highest leaf area index, grain and biological yields harvest index and protein content were achieved by application of 90 kg nitrogen and 20 kg of zinc sulfate per hectare. It seems that the use of zinc with appropriate rates, through its involvement in physiological processes and nitrogen metabolism in plants as an essential element, accelerates green beans growth processes and increases green bean yield.

Controling weeds at their critical periods of growth leads to low production costs and injurious effects of using chemical weed controling methods. In this experiment we studied the timinig effects of weed control (interference of weeds after 20, 40 and 60 days and complete control of weeds) and weed interference periods for 20, 40 and 60 days after planting and complete interference) on growth and yield of forage maize CV. 454. The experiment was conducted incomplete randomized blocks design with three replications at the Research Farm of Islamic Azad University of Tabriz Branch in 2013. According to the results, maintenaning the farm for 40 and 60 days under weed interference after 20 days prevented reduction of maize biomass, while weeds interference after 20 days, weed interference and controling weeds after 40 and 60 days resulted in 41.2%, 35%, 25% and 32.5% reduction of forage maize biomass, respectively. Reduction in fresh weight of corn and fresh weight of leaf and stem were also observed due to interference of weeds after 20 days. If weeds are controlled after 60 days, reduction of corn weight and fresh weight of stem will also results in reduction of biomass. Also, if weeds are controlled after 40 days, stem fresh weight of maize will result in biomass reduction. Corn traits were affected by weeds control treatments. Being affected by treatments of weeds interference after 20 days, weeds non-interference, controlling weeds after 40 and 60 days, the height of corn was reduced by 29.9%, 41.4%, 27.6% and 37.2%, respectively. The stem diameter demonstrated a significant reduction, although it was only affected by treatments of weeds interference and weeds control after 60 days. Based on the results of this study, it may be suggested that controling weeds during initial 20-60 days of maize growth would prevent the undesirable effect of weeds on growth, production and biomass production of maize and also results in production costs.

To evaluate the effects of dose and application time of oxadiargyl, as a postemergence herbicide, on weed biomass and tuber yield of potato, a factorial experiment based on randomized complete block design with 3 replications was conducted at Alaroog Research Station at the University of Mohaghegh-Ardabili in 2013. Treatments consisted of oxadiargyl dosages (0, 0.05, 0.1, 0.2, 0.4, 0.6 and 0.8 lit a.i /ha), and its time of applications at different potato growth stages (potato emergence, stolon initiation and potato tuber bulking), weed free treatment was considered as control. Statistical analysis showed that 0.8 lit a.i/ha of oxadiargyl reduced biomass of weed by 66.16 percent. Oxadiargyl application at emergence time resulted in highest percent reduction of weed biomass. Results, also, showed that application 0.8 lit a.i/ha of oxadiargyl, after weed free condition, increased number of seed tuber and total tuber yield by 82.16 and 51.59 percent respectively, but it reduced number of non seed tuber by 43.17 percent. Application of oxadiargyl at emergence time, as compared with the other application times, resulted in highest increase in the number of seed tuber and total tuber yield, but it did not affected number of non seed tubers. Interaction effect of dose by time of oxadiargyl application revealed that using 0.8 lit a.i/ha dose at potato emergence time increased number of edible tubers by 100%. It may be conducted that application of this dose at potato emergence time was highly efficient in controlling weeds and increasing potato tuber yield.

Experiments, in Petri dish and greenhouse, were carried out to investigate the efficiency of three herbicides (rimsulfuron, imazapic and imazamox) in controling broomrape. In Petri dish study, herbicides were applied at 0.05, 0.25, 1.25, 6.25 and 31.25 micro-mole doses to broomrape seeds at germination stage without a host plant and adding GR24 as stimulator. In the greenhouse experiments, the efficiency of these herbicides to control broomrape in two varieties of tomato (Viva and Hyb.Petopride II) was investigated. Treatments were four doses of rimsulfuron (25, 50, 75 and 100 g ai/ha), imazapic (5, 10, 15 and 20 g ai/ha) and imazamox (0.4, 0.8, 1.2 and 1.6 g ai/ha) at one, two and three applications. Results of Petri-dish experiments showed that rimsulfuron and imazapic significantly reduced radicle elongation of seedlings as compared to the control, while, imazamox did not have any effect on broomrape seed. Each dose was applied for one, two and three times with in 15, 29 and 43 days after within transplanting tomato seedlings. Results of pot experiments indicated that the responses of two tomato varieties herbicides were different. Viva was responsive to herbicidal effect and produced higher biomass than Hyb.Petopride II. Rimsulfuron was a suitable herbicide in tomato to control broomrape. Rimsulfuron at doses of 25, 50 and 75 g ai/ha (three times of application) were the best doses, specially in viva were the best treatments for broomrape control and producing tomato biomass. Imazapic also, at 5 g ai/ha (two times of application) and 10 g ai/ha (single application) was an effective treatments in variety of viva. Imazamox treatments did not appear to be suitable herbicides in this study.

To understand germination and emergence characteristics of black henbane, ground cherry and curly dock a laboratory experiment, based on randomized complete block design with four replications, was carried out at the Faculty of Agriculture, Ferdowsi University of Mashhad in 2012. Treatments were temperature ranges (5/15, 10/20, 15/25, 15/30 and 20/35 ° C night / day) and different levels of salinity (0, 10, 20, 40, 80, 160 and 320 mM of NaCl). The effect of pH adjusted to 5-9 by using acid buffer solution. Seeds were planted at different depth (0, 1, 2, 3 and 4 cm) to study their effects on seedling emergence. Results showed that black henbane exhibited highest germination percentage at 25/15 diurnal tempratures, with 86.50 and 60.50 respectivly for daylight and complete darkness. Germination of ground cherry was highest (93%) at 10/20 diurnal temprature and 41% in complete darkness. Highest germination percentage for curly dock at diurnal temperatures of 20/10, 25/15 and 30/20 with light / dark regime of constant darkness was abserved. The seeds at diurnal temprature of 35/25 in both light regimes did not germinate. Increasing salinity reduced germination. Increasing the osmotic potential, also reduced germination significantly. Highest germination percentage of black henbane (97%) was observed at pH 7, and lowest germination (17%) at pH 9. Increasing planting depth reduced seedling emergence significantly. Germination percentages of ground cherry and curly dock at pH 6 and 7 were highest (97% and 96% respectively) and lowest 26 and 25 % respectively at pH 9.

To study the effects of ascorbate and temperature on antioxidant enzymes and germination indexes, a factorial experimental based on completely randomized block design with three replications was conducted at the Agricultural Research Laboratory of Mohaghegh Ardabili University in 2014. Treatments were three levels of ascorbate (control, 5 and 10 mM) and three levels of temperatures (15, 25 and 35 °C). Parameters under study were germination indices, production rates of antioxidant enzymes, proline and protein. The results of experiment indicated that ascorbate application that of raised proline content. Application of ascorbate resulted in enzymes reduction at 15°C more than 25°and 35° temperatures. Its application also reduced protein denaturation. Since sesame is a warm season plant, it seems that increasing antioxidant enzymes at 15°C is due to higher production of free radicals. The positive and significant correlation between antioxidant enzymes and germination indices represents their direct relationships. According to the results of this experiment, it seems that the application of ascorbate had positive effect on germination indices and reduced the effects of improper temperatures; it also benefited seedling growth of sesame.