THE EFFECT OF AUXIN TYPE AND CONCENTRATION ON PECAN (CARYA-ILLINOINENSIS) SOMATIC EMBRYO MORPHOLOGY AND SUBSEQUENT CONVERSION INTO PLANTS

Embryogenic cultures were initiated from immature pecan zygotic embryo s. Explants were induced for one week on Woody Plant Medium with eithe r alpha-naphthaleneacetic acid or 2,4-dichlorophenoxyacetic acid at 2, 6 or 12 mg/l, then subcultured monthly to fresh basal medium. Observa tions were made on callus production, embryo formation, and embryo mor phology. Somatic embryo morphology and overall callus proliferation we re affected by auxin type. Callus proliferation was less extensive and more somatic embryos resembling zygotic embryos were obtained from cu ltures initiated with alpha-naphthaleneacetic acid than with 2,4-dichl orophenoxyacetic acid. Repetitive somatic embryogenesis was obtained i n all auxin treatments. Conversion into plantlets was affected by soma tic embryo morphology in that embryos with poorly developed apices exh ibited lower percentages of conversion than those with well developed single or multiple apices, Consequently although more embryos were obt ained with 2,4-dichlorophenoxyacetic acid, naphthaleneacetic acid was the superior auxin for production of somatic embryos more likely to co nvert into plants.