Ultrastructural changes during growth and embryogenesis in carrot cell cultures.

摘要: Clumps in suspension cultures of wild carrot have two histological regions; an inner region highly vacuolate, nondividing cells and a peripheral small meristematic cells. Significant ultrastructural features the include presence many starch-filled plastids, dense background free ribosomes, rough ER bearing conspicuous polyribosomal aggregates, numerous multivesicular bodies apparently derived from dictyosomes. Multivesicular fuse with plasmalemma, releasing their contents into wall space. Cell enlargement is accompanied by increase ER, eventual decrease ribosomal content, types structural alteration walls which eventually cause clump disintegration release smaller fragments. Ultrastructural changes accompanying formation embryos auxin-free media striking loss appearance microtubules. The mechanism embryo polarization discussed.