科研之友
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摘要
From two distinct ecotypes of Stellaria longipes, one genotype was chosen from each of two very different locations, an alpine (sun) and a prairie (shade) habitat. Plants were clonally propagated and grown in controlled environment chambers under low and moderate red to far-red (R/FR) ratios. The prairie ecotype plants exhibited increased stem elongation, leaf expansion and flowering (6-fold) in response to a low R/FR ratio, relative to plants grown under the moderate R/FR ratio. In contrast, plants of the alpine ecotype showed no increased growth in response to a low R/FR ratio and their flowering was reduced, all relative to the plants grown under the moderate R/FR ratio. These different phenotypic responses to the reduction in R/FR ratio were associated with very different profiles and concentrations of endogenous cytokinins (CKs) assessed in growing tissues of the upper shoots. Specifically, increased total CKs were associated with the rapid growth of plants of the prairie ecotype under a low R/FR ratio. In particular, concentrations of bioactive trans-zeatin and dihydrozeatin, were increased during the period of most rapid shoot growth by 2- to 4- fold for these prairie ecotype plants grown under the low R/FR ratio treatment. In contrast, changes in CK levels for the alpine ecotype plants grown under low R/FR ratios were muted. Of especial interest, plants of the alpine ecotype had a predominance of cis-pathway CKs, whereas the low elevation, prairie ecotype plants accumulated predominantly trans-pathway CKs. Speculatively, the pattern emphasizing trans-pathway CKs may be explained by increased LONELY GUY enzyme activity. This enzyme converts and activates nucleotide CKs to free base CKs (bypassing riboside CKs). It could thus explain, in part, the prairie ecotype%26apos;s ability to respond to shade light with such a high degree of plasticity if one assumes that high trans-CKs levels are causal for the increased shoot growth seen under a low R/FR ratio.
- 出版日期2012-12
