Abstract
The plants obtained by crosses between C3 and C4 species in Atriplex were determined to be hybrids in views of morphology and δl3C values. One F1 plant of A, triangularis (C3, n=9) x A, rosea (C4, n=9) and one of the reciprocal cross had good pollen and seed fertilities. No prominent differences were observed between these reciprocal Fis in morphological characters. Most of the F2 plants showed a high pollen fertility (more than 70%), and 19 out of the 20 plants so far examined formed normal bivalents. A, triangularis has an opposite phyllotaxis, while A. rosea has an alternate one. Segrega-tion of the F2 for the phyllotaxis was accounted for by assigning two recessive genes to the alternate form. The bundle sheath cells of F2 were many in number but small in size. A very small number of chloroplasts were sporadically observed in the bundle sheath cells in a few plants. Photosynthetic properties of the F2 were examlned in terms of light-photosynthetic curves, transpiration rates and carbon isotope discrimination values (δl3C). In some F3 plants observations were made on the C02 compensation points, photo-respiration activities and several enzyme activities relating to the C4 photosynthesis. No plants with C4-like photosynthetic activities have been found in the F2 nor F3, so far. Possible reasons why no C4-Iike plants were found in the F2 were discussed.
