| The physiology of the green alga Chara was studied in terms of cytoskeleton organization, hormonal responses, and spermatozoid development. Similar to land plants, there are three MT systems during the mitosis of spermatogenesis: cortical interphase array, mitotic spindle, and phragmoplast. F-actin is organized as a reticulate network under the cell wall at interphase and as F-actin plates at the cell poles during mitosis. Like land plants, F-actin is also found at the phragmoplast position. During cell differentiation, both MTs and F-actins are found at the manchette and flagellate position.;Similar to land plants, MTs in the antheridia were depolymerized by auxins, but Chara showed different sensitivity to IAA and alpha-NAA. The internodal elongation and rhizoid development responded to the inactive form of NAA, beta-NAA, which is different from the land plants. alpha-NAA decreased the endogenous IAA and ABA concentrations.;The spermatozoid release process and related spermatozoid activity were affected by the cytoskeletal drugs Lat B and oryzalin and the ATPase inhibitor BDM, which indicates the envolvement of MTs and actins in these processes. That spermatozoid expansion was promoted by Lat B and inhibited by oryzalin indicates both MT and actin are required to keep the proper shape of the spermatozoid.;In conclusion, Chara has some unique characteristics in cytoskeletal structure and physiology but shares many features with land plants. My observations confirm the evolutionary proximity between Chara and land plants. |
