A seed marks the transition between two developmental states; a plant is an embryo during seed formation, whereas it is a seedling after emergence from the seed. Two factors have been identified in Arabidopsis that play a role in establishment of repression of the embryonic state: PKL (PICKLE), which codes for a putative CHD3 chromatin remodeling factor, and gibberellin (GA), a plant growth regulator. Previous observations have also suggested that PKL mediates some aspects of GA responsiveness in the adult plant. To investigate possible mechanisms by which PKL and GA might act to repress the embryonic state, we further characterized the ability of PKL and GA to repress embryonic traits and reexamined the role of PKL in mediating GA-dependent responses. We found that PKL acts throughout the seedling to repress expression of embryonic traits. Although the ability of pkl seedlings to express embryonic traits is strongly induced by inhibiting GA biosynthesis, it is only marginally responsive to abscisic acid and SPY (SPINDLY), factors that have previously been demonstrated to inhibit GA-dependent responses during germination. We also observed that pkl plants exhibit the phenotypic hallmarks of a mutation in a positive regulator of a GA response pathway including reduced GA responsiveness and increased synthesis of bioactive GAs. These observations indicate that PKL may mediate a subset of GA-dependent responses during shoot development.

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With the increase over the past two decades in interest in critical thinking instruction, reliable and valid means for measuring critical thinking are necessary. The Minnesota Test of Critical Thinking was developed to measure critical thinking as defined by the American Philosophical Association in 1990. The present purpose was to explore the structure and reliability of the intervention and its instantiation of the critical thinking framework. Analyses of responses from 151 adult participants gave estimates of reliability varying from .29 to .78. A factor analysis of the test scores supported critical thinking conceptualized as a single, latent trait. With further refinement, the invention should become a valuable measure of general critical thinking skills of upper-division secondary and postsecondary students.