Bahman Jafari; Mojtaba Kordrostami; Ali Akbar Ghasemi-Soloklui
Abstract
Seed germination is a crucial stage in the life cycle of plants. It determines their growth and reproduction success. Temperature is one of the most important environmental factors that affect seed germination. This research aimed to estimate the cardinal temperatures and the thermal time requirement ...
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Seed germination is a crucial stage in the life cycle of plants. It determines their growth and reproduction success. Temperature is one of the most important environmental factors that affect seed germination. This research aimed to estimate the cardinal temperatures and the thermal time requirement for seed germination. The effects of different temperature levels were evaluated on the germination characteristics of tomatoes (Lycopersicon esculentum cv. ‘Early CH’). An experiment was conducted using a completely randomized design with four replications and seven temperature levels, i.e. 5, 10, 15, 20, 25, 30, and 35 ° C. The relationship between germination rate and temperature was described and the cardinal temperatures for the seed germination of tomato (cv. ‘Early CH’) were calculated. Four regression models were used: segmented, dent-like, original beta, and modified beta. The highest germination percentage (81-86%) and vigor index (4.04-5.47 cm) were similarly obtained in the 20-30 °C range. The highest germination rate (5/7 seeds per day) was observed at 25 °C. The lowest mean germination time (4.5-4.84 days) occurred in the 20-25 °C range. Germination characteristics were significantly different when the temperature increased above 30 °C. While measuring the regression models, the segmented model was best for estimating the cardinal temperature of this cultivar. In general, cardinal temperatures for seed germination were estimated using a superior regression model for minimum (0.5-3 °C), optimal (25-26 °C), and maximum (35.4-40 °C) temperatures. Additionally, the thermal time model accurately predicted the seed germination process (R2 = 0.90). The amount of thermal time to achieve 50% germination in this cultivar was estimated at 1848.29 degree-hours.
Vahideh Narjesi; Javad Fatahi Moghadam; Ali Akbar Ghasemi-Soloklui
Abstract
A prevalent problem in pomegranate fruit (Punica granatum L.) is sun damage that decreases the quantity and quality of fruit. The objective of the current research was to evaluate the effects of different photoselective shade net colors and shading percentages on growth traits and pomegranate fruit quality ...
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A prevalent problem in pomegranate fruit (Punica granatum L.) is sun damage that decreases the quantity and quality of fruit. The objective of the current research was to evaluate the effects of different photoselective shade net colors and shading percentages on growth traits and pomegranate fruit quality for two years (2019 and 2020). Plots of pomegranate trees (cv. Malase Saveh) were covered to full canopy with two colors of photo-selective shade nets (white and green) and with two shading percentages (30 and 50%), compared to uncovered plots (control). The experiment was carried out in the Saveh region in the same orchard at the time of fruit set (10 June) and the shading treatments were maintained on the trees for four months. The findings showed that shade nets increased relative leaf water content while decreasing temperature and light intensity in the canopy, compared to the control. Pomegranates under nets had a much higher fruit weight and yield than those on uncovered trees. The percentage of sunburn on fruits was dramatically reduced when a shade net was used. In uncovered trees, the percentage of sunburn was 27.85%, whereas in shade treatments, the percentage of sunburn was 0 - 4.5%. The white shade net allowed 50% PAR (Photosynthetically Active Radiation) and caused the highest fruit weight, juice percentage, aril weight and yield, maximum color of fruits and arils, as well as the lowest level of proline content among the shading treatments. The highest values of total anthocyanin (55.13 mg/100 mL), total phenolics (34 mg GAE/100 mL) and vitamin C (21.32 mg/100 mL) were observed after using the white shade net of 50% PAR. As a result, this type of net is recommended for pomegranate orchards because of its efficiency in improving yield and marketable fruits.
