Phylogeny, habitat together with biological and ecological factors can influence germination of 36 subalpine Rhododendron species from the eastern Tibetan Plateau

Abstract

The reproductive stages of the life cycle are crucial in explaining the distribution patterns of plant species because of their extreme vulnerability to environmental conditions. Despite reported evidence that seed germination is related to habitat macroclimatic characteristics, such as mean annual temperature, the effect of this trait in controlling plant species distribution has not yet been systematically and quantitatively evaluated. To learn whether seed germination can predict species distribution along altitude gradients, we examined germination data of 36 Rhododendron species in southeastern Tibet originating from contrasting altitudes, habitats, plant heights, seed masses, and phylogenies. Germination varied significantly with altitude, habitat, plant height, and phylogeny and was higher in the light than in the dark. Germination percentage was highest at 10:20°C in the light and 15:25°C in the dark. As altitude increased, germination percentages first rose and then decreased, being highest at 3,500–4,000 m. Germination percentage and rate were highest on rocky slopes, increasing as seed mass and plant height rose. Variations in germination percentage and rate were not significant at subgenera, section, and subsection levels, but they were significant at species level. The results suggested that the relationship between germination and altitude may provide insights into species distribution patterns. Further, germination patterns are a result of long‐term evolution as well as taxonomic constraints.

Assessing inter‐intraspecific variability of leaf vulnerability to embolism for 10 alpine Rhododendron species growing in Southwestern China

“…Importantly, the findings demonstrated that genetic differentiation was the primary factor driving this variation in xylem embolism resistance in these ten species, considering that they were grown in a homogeneous nursery. These results provide a theoretical foundation for understanding the extensive distribution of Rhododendron species across elevations ranging from a few hundred meters to 5500 m above sea level (Wang et al, 2018; Wang et al, 2014) and their species diversity within alpine ecosystems (Xia et al, 2021). Moreover, this variability can guide the selection of Rhododendron species that are better adapted to different arid habitats based on their leaf xylem vulnerability to embolism.…”

Response Mechanisms of Woody Plants to High-Temperature Stress

“…The seed germination stage is sensitive to the external environment; there are many factors that affect the seed germination stage, and temperature is one of the main environmental factors that determine seed germination [7]. When the temperature exceeds a certain limit, the water absorption and oxygen intake of seeds is limited [8], significantly affecting germination time, slowing the germination rate and reducing the germination potential [9].…”