Global Ecology and Conservation (Aug 2023)
Seed germination response to diurnally alternating temperatures: Comparative studies on alpine and subalpine meadow populations
Abstract
Germination is considered one of the most important stages influenced by environmental factors, with timing and abundance determining plant establishment and recruitment. However, seed germination traits in alpine/subalpine grasslands are poorly understood, despite alpine/subalpine plant populations are vulnerable to climate warming. In order to investigate seed germination response to diurnally alternating temperature (ΔT) and figure out the response differentiation between alpine and subalpine meadow plant populations, we sampled seeds from 140 populations representing 70 species across an elevation gradient on the eastern edge of the Tibetan Plateau. Seeds were exposed to two ΔT treatments to estimate the germination-related traits. Our results showed that germination characteristics in alpine/subalpine meadow populations were closely linked to ΔT. Under higher ΔT, both subalpine and alpine meadow plants exhibited longer MTG (mean germination time) and lower SYN (germination synchrony). The MTG of subalpine and alpine meadow populations were significantly prolonged by 1.40 d and 0.78 d, respectively, and the SYN were reduced by 0.07 and 0.04 respectively, under higher ΔT. The GNP (germination percentage) and UNC (germination uncertainty) of subalpine meadow plants also had significant differences between the two temperature treatments, indicated that subalpine meadow plants were more sensitive to ΔT changes. Furthermore, under higher and lower ΔT treatments, mean MTG of alpine plants was prolonged by 1.010 d and 1.397 d for each 1 mg increase in seed mass, respectively, and the mean SYN decreased by 0.017 and 0.019 for every 1 mg increase in seed mass, respectively. However, subalpine meadow plants only showed a positive correlation between UNC and seed mass, and a negative correlation between SYN and seed mass at higher ΔT when controlling for the effects of phylogeny, life history and plant size. Our results also suggest that rapid synchronous germination and delayed asynchronous germination coexist in taxa.
