Variations in seed characteristics among and within Stipa purpurea populations on the Qinghai–Tibet Plateau

Abstract

Variation in seed size is common among plant species, populations, and individuals. On the Qinghai-Tibet Plateau, previous studies have mainly focused on interspecific variation in seed size, with little information available regarding intraspecific variation. The alpine steppe is among the most important vegetation types on the plateau, where it plays a vital role in preserving landscape heterogeneity and diversity. Stipa purpurea Griseb., endemic to the Qinghai-Tibet Plateau, is the predominant species of the alpine steppe. In the present study, we measured seed characteristics of nine S. purpurea populations and analyzed possible sources and consequences of variation in these characteristics. Seed characteristics varied greatly among and within populations. Our findings suggest that variation in seed size and awn length may affect germination and dispersal, respectively. Surprisingly, environmental factors rather than genome size were significantly correlated with seed size. For example, relative humidity and number of windy days were strongly correlated with seed size and awn length, respectively. We believe that variation in seed characteristics is a consequence of complex environmental conditions correlated with longitude and latitude. The results indicated that variation in seed characteristics of S. purpurea is an adaptation to environmental conditions.

Potential Effects of Awn Length Variation on Seed Yield and Components, Seed Dispersal and Germination Performance in Siberian Wildrye (Elymus sibiricus L.)

“…The observation that awn length was negatively correlated with latitude and longitude but positively correlated with altitude (Table 4) reflected that awn length varies with environmental variables across locations. A previous study has obtained a negative correlation between awn length and geographical conditions, such as latitude and altitude [31]. Collectively, the majority of correlations between geographical factors and seed traits observed here were not significant but the observed variation in seed traits across locations indicated that seed yield in Siberian wildrye was impacted by interactions between geographical factors and seed yield components.…”

“…Other study indicated the rapid emergence of awned seeds than awnless seeds may be due to their high carbohydrates reserves [25]. A laboratory study reported a negative correlation between awn length and seed germination rate in Stipa pupurea [31]. Our analyses showed a significant negative relationship between awn length and germination percentage among Siberian wildrye populations ( Table 7).…”

“…Previously, seed number varied significantly and showed a slight contribution to harvested seed yield in Leymus chinensis [10]. Other studies obtained similar results in wheat [9,12] and Stipa pupurea [31]. Contrarily, in some species, such as rice, reduced grain number by awns decreased harvested grain yield, despite their contribution to grain size increment [32], implying that seed yield increment by long awns depends on a significant increase in seed size that compensates reductions in seed number.…”

“…A balance and interaction between different yield components may be the key factors that regulate and affect seed yield. Furthermore, seed yield is affected by the interaction of seed yield components, genetic mechanisms and agronomic and environmental factors [2,6,31]. Analyzing this interaction in different grass species would be a valid method for identifying awns' impact on seed yield.…”

“…Geographical factors, such as latitude, longitude and altitude, have been regarded as the major contributors to yield variation in several plant species [36]. It was shown that changes in latitude, longitude and altitude may result in variation in temperature, radiation, moisture and soil fertility, which influence seed yield and components [31,35]. Previous data indicate latitude exhibited a positive correlation with seed traits, whereas longitude and altitude showed a negative correlation with seed yield-related traits in several species [37,38].…”