Journal of Plant Ecophysiology
Volume:2 Issue: 1, 2010

This study was conducted to determine the effect of source manipulation at different growth stages on dry matter remobilization, yield and yield components of wheat. In 2008, two factorial experiments laid out under water stress and non-stress conditions based on a randomized complete block design with three replications. Three varieties named: Fincan, Sysonz, and Gasqugen and three treatments D0 = Control (no defoliation), D1 = leaf defoliation (except flag leaf) at booting stage, D2 = defoliation at anthesis, (D2 = D1), and all leaves defoliation at booting stage (D3 = D1) were used. The results showed that Sysonz demonstrated the highest expressions in traits such as plant density; plant height, 1000-grain weight and biomass as compared to the other varieties, but it presented the lowest grain per plant. The highest and lowest grain yields (1.4 and 1.2 g/plant) were obtained for Fincan and Sysonz under non-stress condition, respectively. Regarding to the defoliation treatments, D0 produced the highest (2.985 g/plant) and D3 the lowest (2.142 g/plant) biomasses. The highest (53.95%) harvest index (HI) obtained for D3. Comparison of defoliations indicated that D3 presented the maximum (40.23) HI was among the other treatments. In respect of stress tolerance indices, Gasqugen had the highest value of stress tolerance idex (STI) and it is concluded that this variety is more stable than the other varieties for the yield performance in various conditions.

Low seed germination and seedling stand establishment are main factors in dryland farming for winter wheat production in low rainfall regions (<300 mm annual rainfall) of Iran. Previous studies have shown that salicylic acid (SA) plays positive roles to plants responses to osmotic stress. Therefore, the influence of seed treatment with salicylic acid on germination and seedling growth under drought stress was studied with two wheat cultivars; Roshan as a tolerant and Mahdavi as an intolerant cultivar to osmotic stress. The results showed osmotic stress (10% and 20% PEG) reduced germination percentage, growth rate, vigor index, seedling length and dry weight and also increased leaf cells electrolyte leakage. The effect of 20% PEG was more severe. On the contrary, SA (0.1 and 0.5 mM) significantly improved germination and seedling indices and cultivars responded similarly to interaction of drought and SA. SA, especially at 0.5 mM alleviated the adverse effects of osmotic stress on most recorded parameters. Therefore, it is concluded that SA may have improve germination and seedling growth and establishment of wheat in dryland farming.

In the current study, the effect of water deficit stress or drought on relative water content and cell membrane stabili-ty of dragonhead (Dracocephalum moldavica) was studied in a greenhouse experiment carried out at Islamic Azad University, Jiroft branch, in 2009. It was a split plot experiment based on Randomized Complete Block Design with three replications, in which vertical factor included three levels of drought stress (irrigation when soil moisture reached 75% of field capacity [mild stress], irrigation when soil moisture reached 50% of field capacity [moderate stress] and irrigation when soil moisture reached 25% of field capacity [severe stress]). The results showed that the effect of water deficit stress was significant on relative water content at 5% level and on cell membrane stability at 1% level. Water stress significantly decreased relative water content from 77.69% under mild stress under severe stress. Relative water content increased as manure level increased. As the stress was intensified, the electrolyte lea-kage increased, but it started to decrease under severe stress. The manure treatment of 40 t/ha had the greatest electrolyte leakage (328.89 dS.m-1).

Greenhouse cucumber (Cucumis sativus L.) is a warm season vegetable which is more useful than other greenhouse vegetables. To determine the effects of five transplant ages and three fruit pruning methods on early harvest of greenhouse cucumber cv. Sultan, two independent experiments were conducted based on randomized complete block design with three replications. The treatments in the first experiment included transplant age at four levels [transplants with two cotyledonous leaves (A0), one (A1), two (A2), three (A3) and four true leaves (A4)] and the treatments in the second experiment included fruit pruning with three levels [fruit un-pruning (P0) and fruit pruning up to the height of 30 cm (P1) and 60 cm (P2)]. The results of the first experiment showed that during the first ten days of harvest, the number of fruits produced by transplants with two cotyledonous leaves and one, two, three and four true leaves was 0, 4, 28, 31 and 63, respectively. The early harvest of the transplants with four true leaves was 15 times as much as that of transplants with one true leaf. Total yield of transplants with four true leaves was 1.8 times as much as that of transplants with two cotyledonous leaves. Total yield of transplants with two cotyledonous leaves and one, two, three and four true leaves was 0.716, 0.988, 1.712, 1.228 and 1.308 kg/ha, respectively. The results of the second experiment showed that during the first ten days of the harvest, the yield of the un-pruned plants was 1.7 and 74 times as high as that of plants pruned up to the heights of 30 and 60 cm, respectively. Total yield of un-pruned plants and plants pruned up to the heights of 30 and 60 cm was 1.47, 1.22 and 1.16 kg/plant, respectively. To have early-maturing cucumber cv. Sultan, it is recommended to use transplants with four true leaves and not to prune the fruits of the main stem and just to cut the axillary branches.

The study was carried out to evaluate the effects of the foliar application of salicylic acid (SA) on vegetative growth of maize (single-cross 704) under saline conditions at Agricultural College of Valiasr University, Rafsanjan, Iran in 2009. A factorial experiment based on a completely randomized design with three replicates was used. Spraying treatments consisted of four salinity levels (0, 4, 8, 12 dS.m-1) and three salicylic acid concentrations (0, 100, 200 ppm). Traits such as shoot dry weight, stem length, number of leaves, leaf area and chlorophyll were measured. Results of analysis of variance showed that salinity levels and SA concentrations affected shoot dry weight, stem length, number of leaves, leaf area and chlorophyll content significantly (P<0.01). By increasing sa-linity up to 12 dS.m-1, the above-mentioned traits decreased by 79.96%, 61.2%, 25.6%, 73.31% and 20.42%, respectively. Means comparison indicated that plant vegetative growth traits were improved by increasing SA concentration up to 200 ppm. As a result, these traits increased by 84.64%, 44.65%, 28.20%, 74.94%, and 38.66%, respectively. Salinity and SA interaction had no significant effect on shoot dry weight, stem length, number of leaves, leaf area and chlorophyll of plants.

An important factor in determining water demand and optimum water management at different growth stages of sugar beet seed-bearing plants is crop coefficient (Kc). The crop coefficient (the ratio of sugar beet seed-bearing plant evapotranspiration (ETc) to grass evapotranspiration (ET0)) was calculated at different growth stages. The study was carried out by 6 lysimeters located in research station of Karaj Soil and Water Research Institute, Meshkinabad, Karaj in 2006. Two lysimeters where grass had been cultivated, were used for determining ET0. To determine ETc of sugar beet seed-bearing plants, vernalized roots of sugar beet (200-250 g) were planted in four lysimeters. About 2000 and 1000 m2 were planted by the same crop around the lysimeters of sugar beet seed-bearing plants and grass, respectively. The moisture contents of all lysimeters were measured during the growth period and also after harvest at the depth of 0-60 cm. To compensate soil moisture deficit, the irrigation was carried out after depletion of 40% of available moisture. In addition, precipitation, daily temperature, relative humidity, wind speed, sunny hours and evaporation from Class A pan was measured in a meteorological station located around the grass lysimeters during the growing period. The measured crop factors included root number, total biomass weight, shoot dry weight, root dry weight, flowering stem weight, seed total weight, seed size, standard seed weight, 1000-seed weight, vigor, germination rate and seed viability. ET0 was calculated by evaporation pan and applying pan coefficient (Kp) of Karaj and also by Penman & Mantis method and was compared with the data of grass lysimeter. ETc, ET0 as well as Kc were estimated at different growth stages. The results showed that there was great conformity between two methods of ET0 calculation, i.e. by software CROPWAT and measurement. But at the beginning of the study, the ET0 calculated by grass lysimeters was lower than that calculated by meteorological data. However, over the time, the latter was affected by climatic parameters of temperature and sunny hours and increased with a stronger gradient than the former. This period was from the 50th day on. The results indicated that crop evapotranspiration decreased at the initial stage because of undeveloped shoots and at final stage and at the end of growth period because of shoot yellowing and loss of green area and the need for the decrease in seed moisture during maturation. At the second stage, the crop absorbed greater amount of water and as a result, its evapotranspiration increased because of the fast growth of sugar beet seed-bearing plants and the proliferation of aerial organs. At the third stage, since on one hand the leaf area of sugar beet seed-bearing plants was at its peak and on the other hand, the other organs were green, the evapotranspiration of the crop was in its peak. At initial stages of the growth, ET0 was greater than ETc of sugar beet seed-bearing plants; however, the gradient of these two curves became almost constant over the time and ETc started to sharply decrease from the beginning of the final stage (i.e. about 90th day). The Kc of sugar beet seed-bearing plants at initial, development, middle and final stages was 0.29, 0.89, 1.12 and 0.66, respectively. Sugar beet seed-bearing plants consumed 35.13, 141.93, 273.59 and 65.49 mm water at initial, development, middle and final stages, respectively. Their peak water consumption was at middle stage with a rate of 7.82 mm/day.

An experiment was conducted in research field of Firoozkooh sugarbeet elite seed production station in 2004 to study the effects of different planting and harvesting dates on quantity and quality of sugarbeet monogerm seed. The experiment was a split plot experiment based on a randomized complete block design with four replications. The planting date at three levels (March 18, April 15 and April 29) made the main plot and harvesting date at four levels (harvesting 15, 30, 45 and 60 days after 50% flowering) constituted the sub-plot. After harvesting and threshing, raw seed yield, seed distribution in terms of diameter and thickness and germination percentage were measured. The results showed that the change in planting date significantly affected the occurrence of 50% greening, stem-bearing and flowering in terms of days after planting and intercepted growing degree days (GDD) at 1% probability level, so that the delay in planting date decreased the number of days to 50% greening, stem-bearing and flowering. The main effects of planting and harvesting dates and their interactions had a significant effect on raw seed yield at 1% probability level. The highest sugarbeet raw seed yield (1164 kg/ha) in Firoozkooh was obtained by planting seed-bearing plants in March 18 and harvesting them 45 days after 50% flowering. The delay in planting date significantly decreased the loss caused by seed polishing, while harvesting date significantly af-fected the proportion of undersized seeds so that it decreased as the harvesting date was retarded. The results indicated that the studied factors did not significantly affect the proportion of standard (with diameters of 3.5-4.5 mm) and oversized seeds (with diameter of >4.5 mm). Delayed harvesting date significantly increased seed germination rate while the change in planting date had no effect on this trait.

Maize (Zea mays L.) is one of the most important food crops. The study of the effects of plant density and soil fertility on some agronomic traits in newly released hybrids is important. The experiment was conducted at the Agriculture Research Station, University of Tehran, Iran. It was a split-split plot design with three replications with corn hybrids as the main plots, plant density as the sub-plots and nitrogen levels as the sub-sub-plots. Grain yield per plant and unit area, biomass, harvest index, ear number, kernels per ear and 1000-kernel weight were measured. The interactions of factors were significant. Maximum grain yield.ha-1 was achieved by the hybrid KSC601 at the density of 8 plants.m-2 with the application of 230 kg N.ha-1. The hybrid KSC601 at the density of 7 plants.m-2 with no N fertilizer application showed the maximum harvest index (70.36%). The highest kernel number per ear was obtained at the density of 6 plants.m-2, and the hybrid KSC601 at the density of 6 plants.m-2 and 230 kg N.ha-1 produced the highest 1000-kernel weight. Increasing N application rate from 0 to 230 kg.ha-1 increased 1000-kernel weight by 12%.