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. 2008. Evaluation of leaf physiological and biochemical traits during senescence of the wheat core collection in the Southwest of China. Can. J. Plant Sci. 88: 331Á 337. Agronomical, physiological, and biochemical analysis of the Chinese wheat (Triticum aestivum L.) core collection revealed abundant variation in the indices examined, both within and between ecotype regions. The genotypes from the Yellow-Huai Rivers (YH) region, the Middle and lower reaches of the Yangtze River (MY) region and the Southwest China (SWC) region showed good adaptation as measured by heading date, malondialdehyde content (MDA), and superoxide dismutase (SOD) and catalase (CAT) activities and would have good potential for wheat improvement in SWC.

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The emergence of new biological traits is landmarks of evolutionary progress. However, when, how, and why do they appear? We propose a universal mechanism, a Buffering Mechanism of Evolution to understand these questions. We speculate that all organisms possess this potential buffer capacity. This capacity would be triggered by the pressures, natural or artificial, to express the intrinsic potential variants. The potential buffer capacity of the organism increases for further selections as evolutionary progress occurs. The higher the evolutionary level of the organism, the greater the potential buffer capacity, and importantly, the buffer capacity versus the pressures of selections will result. However, when the pressures are far more than the potential capacity of the targets, the natural or artificial pressures then compromise the genetic buffering system resulting in possible species extinction if the emergence of new traits fails.Natural and artificial selections are the most important evolutionary impetuses that lead to nonrandom changes in allele frequencies. In the long history of life, the pressures from the two selections trigger in the organism magnificent and cryptic pathways to adapt to the environment well for better survival or reproduce more than other individuals in the population, and, there are bilateral events between evolution and selections. Evolution is composed of several levels, from individual organism to genome to single gene, and the rates, routes and grades exist in a most abundant variability among the different species, which are or have been studied extensively and intensively from the era of Charles Darwin.The history of biological evolution is composed of a series of transitions, including the origin of life, the transition from prokaryotes cell to eukaryotes, the coordination of single cell organisms and multi-cellular and the origin of sexual reproduction. Adaptive ability to the environment was the most important index We express our gratitude for the financial support from the