Kinetin-treated Flax Seedlings as Models for the Integration of the Plant Body
AMONG the many morphological experiments performed on various seedlings1 a recent experiment indicated in Fig. 1 seems to be particularly suitable to further the understanding of the growth correlations which are responsible for the integration of the plant body. Seedlings of Linum usitatissimum when decapitated above the first leaf pair always replace the lost top, when the cotyledonary buds grow out vigorously and prevent the development of the buds which are above them in the axils of the first two leaves, because the cotyledonary buds exhibit a much more advanced embryonic development because the cotyledons have a larger area than the first leaves. Kinetin immediately applied in 1 per cent lanolin to the bud of the first leaf caused it to expand, as in other cases2–4, but the cotyledonary shoots, even in this case, grew out more strongly and finally inhibited the shoot pretreated with kinetin (Fig. 1a).
The role of roots, cytokinins and apical dominance in the control of lateral shoot form in Solanum andigena
SummaryThe lateral bud of Solanum andigena has the potentiality to develop as a stolon or as a leafy, orthotropic shoot. Natural stolons are normally only produced from underground nodes, but aerial stolons can be induced to form by the application of a combination of indole-3-acetic acid and gibberellic acid (IAA/GA3) paste to the cut surface; under some conditions both natural or induced stolons are converted to upright, leafy shoots. The presence of roots was found to be necessary for the conversion of a natural stolon to a leafy shoot, but this root effect could be replaced by the synthetic cytokinin, 6-benzylaminopurine (BAP). By using α-14C-BAP it was demonstrated that cytokinin accumulates in the tip of an induced stolon, prior to its conversion to a leafy shoot caused by withdrawal of the IAA/GA3 paste. The application of IAA/GA3 to decapitated plants was shown to influence both the distribution and metabolism of the cytokinin. The possibility that the role of auxin in apical dominance, at least in part, is to control the distribution and metabolism of cytokinins is discussed.
Efficacy for Dealing With Terrorism Precautionary Behavior: Laying the Groundwork for Communication Effectiveness
In order to formulate effective communication and intervention strategies to respond to the widespread lack of preparedness for public health crises resulting from natural and human-made disasters, researchers have developed models describing the interrelationships between factors associated with emergency preparedness decisions. Empirical research has generally assumed that two key elements of most health behavior theories—self-efficacy and response efficacy—additively influence the decision to prepare, despite compelling theoretical rationale for an interactive relationship. The few studies that have investigated interactions in preparedness outcomes have not tested the Social Cognitive Theory prediction that non-zero levels of both efficacy types are required before individuals will engage in any preparedness behavior. Based on the responses of 3,101 participants in the National Survey of Disaster Experiences and Preparedness, this study tested additive, interactive, and conditional main effect hypotheses about the influence of self-efficacy and response efficacy for dealing with terrorism on preparedness due to terrorism six years after the September 11, 2001, terrorist attacks. A significant self-efficacy × response efficacy interaction effect on preparedness was found, in addition to a significant response efficacy effect when perceived self-efficacy was zero, contrary to the expectation from Social Cognitive Theory. These results offer insights into the cognitive processes underlying individuals’ decisions to prepare for disasters such as terrorist attacks, and highlight the importance of considering more complex theory-based cognitive interaction models in designing effective communication strategies to facilitate individual emergency preparedness.