Development of a temperature-based seed germination model for silverleaf nightshade (Solanum elaeagnifolium)

Abstract

Silverleaf nightshade (Solanum elaeagnifolium Cav.) has become a highly troublesome weed in irrigated summer crops in Israel. Since herbicide-based options to control this weed are limited, the best way to improve weed control is through a study of its biology, particularly its germination dynamics. The main objective of this study was thus to determine the impact of temperature on the seed germination dynamics of S. elaeagnifolium and to develop a temperature-based (thermal) prediction model for three S. elaeagnifolium populations growing in different ecosystems in Israel. To this end, a laboratory study was undertaken in which the germination proportion of S. elaeagnifolium seeds were monitored under seven temperature regimes: 2/8, 7/13, 12/18, 17/23, 22/28, 27/33 and 32/38 C (night/day). In addition, the impact of alternating temperature regimes between night and day temperatures (of 0, 2, 4, 6, 8 and 10 C), that were averaged over 20 and 25 C, was determined. It was found that the three populations shared similar germination characteristics and dynamics. An alternation of ≥ 6 C between night and day temperatures was needed for optimal germination, with no germination taking place under constant temperatures. In all three populations, the minimal requirement for germination was a 12/18 C (night/day) regime, with the final germination proportion lying between 0.25 and 0.36. The highest final germination proportion ≥0.8 was observed for the 17/23 C regime in all three populations. Modeling the germination rate as a function of temperature allowed us to determine cardinal temperatures for all three populations taken together, with the values being T b = 10.8 C (base temperature), T o = 23.8 C (optimal temperature) and T c = 35.9 C (ceiling temperature). These biological parameters allowed accurate (RMSE<0.06%) prediction of S. elaeagnifolium seed germination over the entire temperature range.

Modeling the effect of temperature on rhizome sprouting in the invasive weed silverleaf nightshade (Solanum elaeagnifolium)

“…The model's effectiveness in predicting cardinal temperatures and the development of phenological events in various plant species has indeed been demonstrated previously (Cochavi et al 2016(Cochavi et al , 2018Yin et al 1995). Kapiluto et al (2022), who performed a study similar to the current one, but for seeds, revealed cardinal temperatures of 10.8, 23.8, and 35.9 C for T b , T o , and T c , respectively. It may be seen that these values for S. elaeagnifolium seeds and rhizomes differed mainly for T o and T c , which were higher by 12 and 5 C, respectively, among the rhizome fragments.…”

“…at 33 C (Satorre et al 1996) and yellow nutsedge (Cyperus esculentus L.) at 28 C (Li et al 2000), indicating the preference for high temperatures for sprouting of such plants. Furthermore, our results indicate that the maximum sprouting of S. elaeagnifolium rhizomes was higher by 10 C than that for seed germination (Kapiluto et al 2022). In general, rhizomes contain larger carbohydrate reserves than seeds, which in turn enable them to survive and sprout in extreme environments (Anbari et al 2011;Chen et al 2015;Mangoale and Afolayan 2020;Yu et al 2001).…”

“…Based on the GDD computation (Equation 5) and the parameters that were determined via Equation 6, it was predicted that S. elaeagnifolium rhizomes have a lag time of 12 GDD, the 50% sprouting would be reached after almost ∼30 GDD, and the maximum sprouting would be recorded at 80 GDD (Figure 3). Kapiluto et al (2022) showed that for seed germination, the GDD values of the lag, 50% germination, and the maximum germination stages were higher, ∼50, 140, and 180 GDD, respectively. These results further emphasize that rhizomes, as the main S. elaeagnifolium dispersal organ, contribute to the aggressiveness of this weed in agrosystems by rapid sprouting and establishment.…”

“…Recently, Kapiluto et al (2022) developed a comprehensive temperature-based predictive model for S. elaeagnifolium seed germination under a wide range of temperatures. The study revealed the cardinal temperatures for the seed germination of this species, but it was limited in that it did not address the impact of temperature on rhizome sprouting characteristics and dynamics, and hence it does not provide any insights about the cardinal temperatures for this dispersal organ.…”

The Invasive Weed Trianthema portulacastrum in Israel

“…portulacastrum emergence under Israeli climatic conditions, where T. portulacastrum infests crops that are cultivated in the summer, such as maize, tomato, watermelon, setaria, and groundnut. In a similar thermal time model study on the perennial weed Solanum elaeagnifolium in Israel, T base for germination was computed to be 10.8°C (Kapiluto et al, 2022). A seed germination thermal time model was also used by Ottavini et al (2019), who studied the effects of light, temperature, and soil depth on the germination and emergence of the invasive weed Conyza canadensis (L.) Cronq.…”