FLORAL VASCULAR PATTERN IN SOME SCROPHULARIA SPECIES WITH SPECIAL EMPHASIS ON STAMINODE AND NECTARIFEROUS DISK

摘要

Premise of research. Staminode function is very diverse, but in Scrophularia (Scrophulariaceae), nothing is known about it. Some authors postulated that the staminode was associated with nectar secretion in some Scrophularia species but without experimental verification. Besides, there is little information about flower vas-culature of this genus and none about the free portion of the staminode or the disk nectary, essential aspects to investigate, together with field experiments, if staminode is associated with nectar secretion in this genus. Methodology. Flower, staminode, and nectary vasculature were analyzed in the lab for three species with different staminode sizes (S. scorodonia, S. lyrata, and S. canina). We studied cross sections and longitudinal sections of flowers using a rotary microtome and also fixed and submerged flowers in Herr's liquid. For 2 yr in the field, nectar volume and concentration were measured three times per day in control flowers (with staminode) and in flowers without staminode after the staminode extirpation the day before flower anthesis. Pivotal results. The calyx receives five median vascular traces and five fused lateral vascular traces. Each petal and stamen, as well as the staminode, receives only one vascular trace. The vasculature development of the free portion of the staminode is related to the staminode size. Experimental removal of the staminode did not affect nectar volume or concentration. The basal tissue of Scrophularia nectary is intimately linked to that of the gynoecium, being an enation of the ovary. Conclusions. First, the degree of staminode vasculature development is related to staminode size: larger staminodes have more vascular traces than tiny staminodes. Second, the staminode is not associated with the nectary or nectar secretion. In fact, flowers with staminodes do not produce significantly more nectar volume than flowers without staminodes, and nectar concentration is similar in both types. Third, Scrophularia nectary has a gynoecial origin as determined for other Scrophulariaceae.