Description and control of flowering in California Poppy (Eschscholzia californica)

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Virginia Polytechnic Institute and State University

The California poppy (Eschscholzia californica Cham.) has floral marketplace potential provided it can be produced as a well-proportioned potted plant. Its attractive floral display and tolerance of extreme heat and drought make it a good candidate for research aimed at introducing it as a new ornamental crop.

The major objectives of this study were to document the apical meristem changes of California poppy during the transition to flowering, to determine the minimum number of inductive long-day (LD) cycles required for induction and initiation of flowering, and to examine the effects of exogenously applied gibberellin (GA₄₊₇) and auxin (NAA) on reproductive and vegetative development.

Histological examination of apical meristems exposed to varying numbers of LD cycles revealed many changes commonly associated with the onset of flowering. There was an increase in RNA activity in the apical cells, an enhanced doming of the shoot apex, an increased elongation of primordia internodes, a disruption of the tunica-corpus organization, and the appearance of well-developed branch primordia.

Eight to ten LD cycles was identified as the critical range required for successful flowering in California poppy plants when exposure to the inductive photoperiod was begun at the 8 to 12 true, expanded leaf stage.

Exogeneous NAA was shown to have no significant effect on final reproductive status or vegetative development of California poppy. GA₄₊₇ application resulted in an enhanced shift toward reproductive development and an increase in stem elongation, but it had little effect on peduncle elongation. These results indicate that stem and peduncle elongation may be controlled by different mechanisms and warrant further research.

The final chapter of the thesis concerning the design and evaluation of educational programs for the Virginia Tech Horticultural Gardens represents a departure from the major topic of study. This chapter is the result of the author's interest in, and the Garden's need for, an educational program suitable for the general public. This study can be considered the first step in the development of such an educational program.