The Effect Of Seed Size And Altitude On Main Seed Reserves Of Common Plants In An Alpine Meadow On The Northeastern Qinghai-Tibet Plateau

The components and contents of main reserves in seeds is very important to seed germination and subsequent seedling establishment. The different seed germination and seedling growth strategy might be shaped by the difference in contents of seed reserves because different seed reserve plays respective role on seed germination and seedling establishment. The principal reserves of seeds are fats, soluble sugar, starch and protein, which could with environmental conditions, genetic factors and so on. Although seed size is a relatively stable trait, it still has great interspecific and intraspecific variation with changeable environment. Would the content of seed main reserves be changed to adapt to changeable environmental with seed size variation? In this study, the variation in contents of seeds main reserves among species on the northeast Qinghai-Tibet plateau with seed weight and altitudes were analyzed, which could provide a theoretical basis on researches in adaptability of alpine plants. The content of crude fats was determined by Soxhlet extraction with petroleum(60-90℃) as solvent for 8 hours; the content of soluble sugar and starch were determined by anthrone colorimetric method; protein values were obtained by Coomassie Brilliant Blue G-250.The results showed that:(1) The seed size of most species were smaller and ranged from 0.0327 to 26.0323 mg, more than 80% of the species had seed size rangedd between 0-5mg. Seed size was significantly negatively correlated with altitude gradients if all the species were considered, however, within families, such as species in Asteraceae, Fabaceae, Umbelliferae, Ranunculaceae, there was no significant correlation between seed size and altitude.(2) The contents of fat, soluble sugar, starch and protein were all significantly different among 225 species, the variation of fat, soluble sugar, starch and protein content were 5.0533%~57.0799%(fat), 0.5099% ~ 10.4343%(soluble sugar), 1.5589% ~ 57.9976%(starch), 1.0486% ~ 29.5097%(protein), respectively. The content of fat was negatively related with seed size, a significantly positive relation was found between starch content and seed size, however, The content of soluble sugar or protein did not correlate with seed size. Among species in Asteraceae, Legume, Umbelliferae, and Ranunculaceae, there was no consistent relationship between seed size and the content of the main seeds reserves, which might be influenced by genetic, environmental and family differences. Within species, seed size has no significant effect on seed fat, soluble sugar, starch and protein content, which may be due to the influence of environmental factors on seed nutrient content.(3) whether intraspecific or interspecific variation, the content of crude fats and the content of soluble sugar were higher, and the content of protein was lower at high altitude, while the content of starch had no obvious variation with increasing altitude. Because temperature was decreased with increasing altitude, relative higher contents of fat and soluble sugars in seeds at higher altitude might provide enough energy for seed germination and initial growth of seedlings. Therefore, it might be an adaptive selection to alpine environment.