Document Type : Research paper

Authors

• Bahman Jafari ¹
• Mojtaba Kordrostami ²
• Ali Akbar Ghasemi-Soloklui ²

¹ Department of Agronomy and Plant Breeding, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran

² Nuclear Agriculture Research School, Nuclear Science and Technology Research Institute (NSTRI), Karaj, Iran

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 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. 

Keywords

• Base temperature
• Germination parameters
• Germination rate
• Regression models
• Thermal time