Biochemical Characterization of Developmental Stages of Cycad Somatic Embryos

The effect of two light intensities (25 µmol m−2s−1 and 50 µmol m−2s−1) on four developmental stages of Ceratozamia mexicana somatic embryos growing on semisolid plant growth medium at 25oC was measured. Growth parameters included fresh weight, morphology, and invertase and peroxidase activity. Under low light conditions, fresh weight was greater in stages 1 and 2 than in stages 3 and 4. In addition, there was a high frequency of hyperhydricity and polyembryogenesis in stages 1 and 2, whereas stages 3 and 4 were nonhyperhydric and unbranched. Stages 2–4 were green. Under high light conditions, embryos had lower fresh weights and less hyperhydricity, and stages 2–4 were green. Under low light conditions, peroxidase activity was less, although stage 1 embryos under both light conditions showed the highest activity. Stage 1 embryos required three to four months to develop to stage 2 under high light conditions and two to three months under low light conditions. Invertase activity under low light conditions was minimal in stage 2. All embryos had low invertase activity under high light intensity, and stages 2–4 had high levels of glucose. Embryo development from stage 2 to the next and for each subsequent stage under high light conditions required three to four months, and under low light conditions required four to five months. Higher light intensity therefore promotes the speedy recovery of plants.