Quantifying Guar (Cyamopsis tetragonoloba) Seed Germination Relative to Temperature

Guar (Cyamopsis tetragonoloba L.) is a plant from the legumes family. Guar gum is obtained from endosperm in guar seeds. Guar gum is used in many industries such as pharmaceutical and food industries, paper, mining, oil and drilling, textiles, and explosives industries. Modeling is a method that is widely used in predicting plant growth stages and determining the required thermal units in each growing stage, especially germination.Considering the important therapeutic and industrial uses of guar and the lack of sufficient information and reports to determine the cardinal temperatures of this plant, this study aimed to investigate the effect of temperature on germination traits and early seedling growth and predict the cardinal temperatures (minimum, optimal and maximum) of germination for this plant.

This research was carried out at the Seed Sciences and Technology Laboratory of Agricultural College of Sarayan, the University of Birjand in 2017. Experiments were carried out in a completely randomized design with 8 levels of temperature treatments (5, 10, 15, 20, 25, 30, 35, and 40°C), with 5 replications. Germination percentage, daily germination speed, mean daily germination, plumule length, root length, and seedling length were calculated. Cardinal temperatures of germination were calculated using regression analysis with the aid of the proposed models (logistic, two-way, quadratic, and third-order polynomials) using germination speed. The data were analyzed using SAS software and the comparison means were done by Duncanchr('39')s test at a probability level of 5%. Sigma Plot software was used to plot the germination rate against temperature graphs (for fitting different models).

 The results showed that the effect of different temperature levels on the percentage, speed and mean seed germination was significant (P <0.05). According to the results, the lowest values for percentage, speed, and average germination were obtained at 5, 10, and 40°C, and the highest germination speed was observed at 15 °C and also the highest percentage of germination and average germination was observed at 35°C. The results of the effect of different temperature levels on seedling growth showed that the effect of temperature on the seedling length, stem, and root length was significant (P <0.01), so that the lowest values related to seedling length, plumule, and radicle was found at 5, 10 and 40°C, and the maximum seedling and plumule length were 30°C.

Quantification of the gauge seed germination reaction to different temperature levels was carried out using four dual-functions, logistic, quadratic and triple polynomials. The second-order multitasking regression model, based on the coefficient of explanation (R2) and the amount of deviation, had a suitable and significant fit with the data related to germination rate against the independent temperature variable. Based on the parameters of the model, the optimum temperature was obtained at 26.05°C and the minimum and maximum temperature of guar germination were calculated to be 6.09 and 40°C.