Hydrotime analysis of Lesquerella fendleri seed germination responses to priming treatments

Abstract

Lesquerella fendleri seeds contain industrial oil, which is increased under arid environments. In such environments, the water needed for germination is available for only a short time, and consequently, successful crop establishment depends not only on rapid and uniform germination of the seedlot, but also on its ability to germinate under low water availability. All of these attributes can be analyzed through the hydrotime model (HT). Priming is a method to improve the speed and uniformity of germination. This technique reduces the hydrotime constant ( θ H) and sometimes displaces the base water potential ( ψ b(50)). This would increase the ability of the seed to germinate under low water availability. The objective of this work was to improve (i) the velocity and uniformity of germination and (ii) the ability to germinate under low water availability condition, in seeds of L. fendleri. We also intended to analyze and model changes in the physiological behaviour of the seedlot caused by the application of the priming treatment with seeds sown both in Petri dishes and containers with soil placed in the field. Seeds were subjected to priming in Petri dishes with a solution of polyethylene glycol (PEG) at 5 (P5) or 20 °C (P20). One-half of the seedlot was used for determination of hydrotime parameters by incubation in Petri dishes at 10, 20, and 30 °C, and in water or PEG solutions calibrated to obtain different ψ a. The remaining one-half of the seedlot was sown in soil containers. Three different water availability treatments were imposed, field capacity or control, 75%, and 50% of the field capacity with the P5, P20, and untreated seeds. The P20 and P5 seeds germinated faster and more uniformly than the untreated (control) seeds under laboratory and field condition. The HT model analysis revealed that the θ H constant had been reduced and ψ b(50) had been shifted towards more negative values in both the P20 and P5 seedlots. This behaviour was consistent with the higher germination percentage attained by the P20 and P5 seeds in the field conditions under reduced water availability (i.e., 75 and 50% of field capacity) compared with that exhibited by the untreated seeds under the same situations.