Abstract: Seven species of Portulaca growing in Hawaii can be divided into two groups based on the morphology, anatomy, and ultrastructure of their leaves. Portulaca oleracea, P. molokiniensis, P. lutea, forming group A, have spatulate to obovate leaves, paradermal minor veins, and mesophyll cells that completely encircle the minor veins. The chloroplasts in their bundle sheath cells are larger than those in the mesophyll cells and have well-developed grana and reduced peripheral reticulum. Bundle sheath mitochondria are larger and more numerous than those in the mesophyll, and chloroplasts in the mesophyll cells have well-developed grana and peripheral reticulum. Portulaca pilosa, P. villosa, P. sclerocarpa, and P. "ulupalakua," forming group B, have lanceolate to oblong–oblanceolate leaves, peripheral minor veins, and incomplete wreaths of mesophyll cells. The choroplasts in their bundle sheath cells are about the same size as those in the mesophyll and have reduced grana and well-developed peripheral reticulum. ...

Abstract: Ten taxa of Portulaca that occur in Hawaii (P. lutea, P. molokiniensis, P. oleracea, P. pi/osa, P. sclerocarpa, P. villosa, two imperfectly known species, and two cultivars) were included in a study of reproductive biology and uniform cultivation. The response of plants under uniform conditions upholds the merger of the reputed Hawaiian endemic P. cyanosperma with P. pi/osa. All Portulaca taxa in Hawaii are autogamous, and in most instances large numbers of seeds are set even when the flowers are totally undi sturbed. Some taxa are facultatively cleistogamous, but even in chasmogamous forms the flowers are open for only about 3-9 hr. The cultivars were the on ly taxa observed to attract pollinators, but P. molokiniensis, which was not studied in nature, ap pears to have adaptations for biotic pollin ation. Most of the portulac as studied have capsular fruit that require about 13-17 da ys to mature, but in P. sclerocarpa the fruits are thick-walled and indehiscent and require about 28 da ys for maturation. The life cycle ranges from about 8 weeks in most cases to several months in P. molokiniensis. However, individuals of most taxa typically flower and fruit man y times during one growing season. Seeds were generally nondormant, but partial seed dormancy was encountered in P. molokiniensis. THERE HAVE BEEN NO STUDIES focusing on reproductive aspects of Portulaca in Hawaii . The only available comparative information of this sort is found in the revision by Geesink (1969), which dealt with morphology, systematics , biosystematics, and typification of Portula ca from Indo-Australia and the Pacific. However, most of his work was based on herbarium studies. In his revision , Geesink (1969) recognized only three species of Portulaca in Hawaii . In contrast, the recent work of Wagner et al. (1990) recognized the occurrence of six named species and two unnamed taxa of Portu laca in the Hawaiian Islands. Thi s disparity of treatments prompted a broad stud y ofall taxa of Portulaca reported to be native or naturalized in the Hawaiian Islands (Yun 1989). The present paper pro1 This work represents part of a Ph.D. dissertat ion filed with the University of Hawaii at Manoa, Hon olulu , under the name InSun Yun . Manuscript accepted 10July 1989. 2 Department of Botany, University of Hawaii at Manoa, 3190 Maile Way, Honolulu, Hawaii 96822. 3 Current add ress: 10-106 Dornan-dong, Jinhae, Kyongnam, Korea. vides information gained from a study of floral pheno logy, breeding systems , and uni form culture of 10 taxa of the genus Portu laca that occur in Hawaii . MATERIALS AND METHODS The taxa used in this study were Portulaca lutea Sol. ex G. Forster, P. molokiniensis Hobdy, P. oleracea L., P. pi/osa L., P. sclerocarpa A. Gray, P. villosa Cham. , two imperfectly known species designated P. " olowalu" and P. "ulupalakua," a cultivar of P. grandiflora Hook., and a second unidentified cultivar designated P. cv. I. Portula ca "olowalu" is treated as a variant of P. villosa by Wagner et al. (1990). They suggest that it likely represents an undescribed endemic taxon . Portulaca " ulupalakua" corresponds to P. sp. A in the treatment by Wagner et al. (1990), who consider it to be a naturalized, as yet unidentified species. Plants were maintained and studied in the greenhouse for severa l months to 2 yr. Collection and accession data can be found in Yun (1989). In the greenhouse study, randomly selected

Abstract: Portulaca oleracea L. seedlings do not develop in the direction of neighbours, even when these neighbours are small and distant. Neighbouring plants could be simulated by small rectangles of a plastic that resembled leaves in its spectral characteristics. Unlike seedlings, mature plants did not respond to objects that do not influence photosynthetic light. When light of equal intensity was received from all directions, Portulaca seedlings avoided the direction with higher far-red light. Portulaca is thus able to use spectral composition and direction of light as clues for the probability of the direction of future shade.