Authors:H. Bu, X. Chen, Y. Wang, X. Xu, K. Liu, and G. Du
In this paper, 633 species (involving 10 classes, 48 families, 205 genera) collected from the alpine meadow on the eastern Qinghai-Tibet plateau were studied. We tested potential factors affecting variation in mean germination time (MGT), i.e., plant traits (adult longevity, dispersal mode and seed size) or phylogeny, to evaluate if these factors were independent or they had interaction. Nested ANOVA showed that taxonomic membership accounted for the majority of MGT variation (70%), and in the generalized linear model, family membership could explain independently the largest proportion of MGT variation (29%). The strong taxonomic effect suggests that MGT variation within taxonomic membership is constrained. The other plant traits could also explain MGT variation independently (1% by adult longevity and dispersal mode, respectively, and 2% by seed size). Thus, the phylogeny was an important constraint to maintain the stability of species, and we could simplify the question if we regarded the phylogeny as an individual factor, but we could not negate the adaptive significance of the relationship between other plant traits and seed MGT. In addition, a large percentage of the variance remained unexplained by our model, thus important selective factors or parameters may have been left out of this analysis. We suggest that other possible correlates may exist between seed germination time and additional ecological factors (for example, altitude, habitat and post-dispersal predation) or phylogenetic related morphological and physiological seed attributes (e.g., endosperm mass) that were not evaluated in this study.
Tocopherols, tocotrienols and γ-oryzanol are potent antioxidants of rice grains, and they may play an important role in the germination and growth of rice plants. In this study, the objective was to examine the effects of germination time on contents of Toc, T3, GO and ascorbate, as well as enzymatic antioxidant activities in the grains of two different rice varieties, namely TN71 and KS139. Samplings were conducted at 0, 3, 6 and 9 days after imbibition. The results showed that T3 and GO contents, but not Toc increased during seedling emergence. Toc content showed a trend of decrease from 0 DAI to 6 DAI. Contrasting to KS139, the AsA content in the grains of TN71 increased with increasing DAI. KS139 showed a time-dependent increase in the dehydroascorbate level, while that of TN71 remains unchanged at all times. TN71 showed significant increases in superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase activities in the late germination stages (9 DAI); with the exception of APX, KS139 exhibited a relatively constant enzymatic activities throughout the germination period. The changes in the malondialdehyde and H2O2 levels were minimum before 6 DAI, however a significant increase was noted at 9 DAI. This study indicates that besides the enzymatic antioxidants, the increase in T3 and GO contents may play a role in countering the oxidative stress during rice grain germination.
This present work is modelling the three physiological stages of germination. The aim of modelling is to define within germination time the duration of the different stages and their temperature dependence. The periods follow Arrhenius-type relations with (average) activation energies typical for the given stages and according to the germination time as well. The germination time being different seed-by-seed can be considered a random variable of normal distribution according to the model. The result of the model was controlled by experimental data given by seed germination trials of the common reed (
) and in cases using those given on other seeds (rice, pea).