Seed Survival at Low Temperatures: A Potential Selecting Factor Influencing Community Level Changes in High Altitudes under Climate Change

Abstract

In alpine ecosystems, imbibed seeds are often exposed to temperatures as low as À35 C, challenging their survival in the soil. Here, we show that seeds have mechanisms to survive cold climate prevalent in alpine ecosystems and have identified three such mechanisms from existing literature, including two forms of freezing avoidance (the presence of water impermeable seed coats, and the supercooling of seed tissues) and one form of freezing tolerance (by extracellular-freezing). Experimentally-derived published data on the lowest temperature recorded at which 50% of a seed sample survived (i.e., lethal temperature; LT 50) was used to generate a dataset of 24 species across low altitude, boreal and alpine environments. We assumed that the ability of seeds to maintain viability at very low temperatures would increase in species associated with higher altitudes conferring a competitive advantage that would be lost under projected climate change. However, our results reveal to underpin that seeds from boreal species survive relatively better at lower temperatures than those of alpine species. Paradoxically, a warming climate could lead to alpine seed death due to extremes of cold at the soil surface resulting from snow cover loss, whilst the declining snow cover may facilitate boreal forest colonization above the current treeline.

Methods to promote seed germination in the lacquer tree, Toxicodendron vernicifluum (Stokes) F.A. Barkley

“…The seeds of several species with physical dormancy are known to exhibit extremely high cold tolerance. In addition, the water-impermeable endocarps of dried seeds protect embryos from freezing by blocking the ingress of water from the outside environment [ 35 ]. Iwate Prefecture—the main producer of urushi in Japan—experiences a lot of snowfall, and temperatures often fall below minus 10 degrees.…”

The seed germination spectrum of 486 plant species: A global meta-regression and phylogenetic pattern in relation to temperature and water potential

“…Germination at subzero temperatures is likely because proteins and sugars in plant cell that protect cell environment from damages caused by ice formation. A recent study (Jaganathan et al, 2020) proposed three main mechanisms for sustaining survival at subzero temperatures, including the existence of water impermeable seed coats, the super-cooling of seed tissue and freezing tolerance triggered by extracellular-freezing. Species included in our study might take advantage of these mechanisms to ensure their survival at subzero temperatures.…”

Genomic Insights into High-Altitude Adaptation: A Comparative Analysis of Roscoea alpina and R. purpurea in the Himalayas

“…Plant populations across altitude gradients exhibit genetic differentiation and local adaptation to specific environmental conditions [8,9]. High-altitude plants often exhibit genetic adaptations for cold tolerance to withstand freezing temperatures and frost [10]. They have genetic adaptations to cope with high light intensity and UV radiation [11].…”