Quantifying Temperature and Osmotic Stress Impact on Seed Germination Rate and Seedling Growth of Eruca sativa Mill. via Hydrothermal Time Model

Abstract

Germination models are quite helpful in predicting emergence times, dormancy periods, and their applications in crop management. This study investigated the germination behaviors of Eruca sativa Mill. in response to fluctuations in temperatures (Ts) and water potentials (ψs). Germination percentage (GP) increased 95% with rising temperature within the range of 20–30 °C, and decreased 25% at 5 °C. Moreover, each ψ and T resulted in a decrease in GP as ψ decreased. Further, we noted that the θT1 value was substantially high at 30 °C and in (0 MPa), whereas the θT2 value was maximum at 10 °C (−0.02 MPa) and it decreased with decreasing Ψ. The maximum hydrothermal time constant (θHTT) and hydrotime (θH) values were obtained at 10 and 30 °C, respectively. In addition, a linear increase in the GR(g) pattern was observed at Tb and a decrease below the To. The calculated cardinal Ts was 5 °C for the base T, and 30 °C for both the optimum and ceiling T. The germination characteristics were higher at 30 °C having (0 MPa). Therefore, using cardinal temperatures, germination results, and the hydrothermal time model (HTT) could reveal the independent and interactive impacts of both T and the Ψ on the response of seed germination subjected to diverse environmental conditions.

Validating the Impact of Water Potential and Temperature on Seed Germination of Wheat (Triticum aestivum L.) via Hydrothermal Time Model

“…Later on, Ts > To, the θH was constant (2.4 MPah −1 in Pirsabak 15 and 0.96 MPah −1 in Shahkar), and only Ψ b(50) was raised with the rising temperature, which resulted in an increase in germination times and a decline in germination rate. Likewise, previous studies on potatoes [17] and watermelon [7] observed an increase in θH numerical quantity at sub-optimal TT. The θH value can be used in a seed lot as a seed quality indicator, as reported previously [35].…”

“…The To value (20 • C) was also measured to be closer to that described by [37,38], who reported the To for Triticum aestivum germination ranged from 20-25 • C. The Tc value at 35 • C observed was equal to the Tc value in this study exported by [38] (above 31 • C), [37] (above 30 • C), and [39] (35-42 • C). [28] proposed that using the hydrothermal time models (Equations ( 5) and ( 7)) along with a standardization factor ([1-(Ψ/Ψ b(g))] tg), all tg at constant temperature and solute potential are measured on a thermal time scale, which bears the same finding in watermelon [7] and potato [17]. In the present study, we used this factor.…”

“…In a similar climate study, the researchers predicted that wheat yields would reduce by 6%, equivalent to a possible 42 Mt/°C [ 5 ]. The continuous change in climate conditions has led to an increase in environmental stresses, which negatively impacts the development, growth, and productivity of important crop species, including wheat [ 6 , 7 , 8 , 9 ]. Therefore, adaptation strategies need to be designed to maximize yield for continuously increasing food demands in the face of continuously changing climatic conditions.…”

“…In order to understand how and why germination in various environmental conditions is affected, seedling growth models are employed. A number of studies have examined the effects of temperature (T), water potential (ψ), and the interaction between T × ψ on germinating seeds via thermal, hydrothermal, and hydrotime models [ 7 , 13 , 14 ].…”

“…The hydrothermal (HTT) time model measures the germination time concept across T and ψ in the sub-optimal range (between Tb-To) and with alteration, as well as in the supra-optimal range (between Tb-Tc [ 7 ]. So far, several species have adopted this approach.…”