Totipotency and embryogenesis in plant cell and tissue cultures

Summary An important development in the field of plant cell and tissue culture has been the demonstration in the past decade of the totipotency of higher plant cells. Isolated single cells were first successfully grown on a nurse tissue separated by a filter paper and gave rise to a callus tissue. Later, completely isolated single cells of tobacco were grown in microchambers to form small clumps of cells which then could be differentiated to form adult tobacco plants. Indirect evidence of the totipotency of higher plant cells has also been provided in a number of other plants. Embryo-like structures (or embryoids) or whole plants, or both, have been obtained from such highly differentiated cells as the pollen grains (gametic and haploid), photosynthetic palisade cells in leaves, epidermal cells from the hypocytyl, and the triploid endosperm cells; all of these cell types perform very highly specialized functions in the plant. Plant protoplasts (cell wall is digested with enzymes) have also been cultured to give rise to normal adult plants. In many instances embryoids have been produced in vitro from several species of flowering plants which do not show such asexual activity in nature. These embryoids are normally indistinguishable morphologically from embryos produced by gametic fusion, often follow the same pattern of cell divisions and differentiation as the developing zygote, and are economically important as they provide clonal populations. Early work in this area emphasized the necessity of dissociating tissues into single cells and providing a nutritional environment identical to that of the zygote in the embryo sac (usually by supplementing the medium with liquid endosperm from coconuts), before the cells could be released morphogenetically to express their totipotency by forming embryoids. Much of the recent work, however, has shown that perfect development of embryoids can be obtained in completely synthetic media in callus tissues as well as in suspension cultures. This paper is dedicated to the memory of the late Professor Philip R. White, a dear friend who provided much counsel and inspiration to us both. for his pioneering work, valuable contributions and untiring efforts in developing the science of plant cell, tissue, and organ culture. Florida Agricultural Experiment Stations Journal Series No. 4699. Presented in the Symposium on Functional Differentiated Systems at the 23rd Annual Meeting of the Tissue Culture Association, Los Angeles, California, June 5–8, 1972.     

Spaceflight reduces somatic embryogenesis in orchardgrass (Poaceae)

Somatic embryos initiate and develop from single mesophyll cells in in vitro cultured leaf segments of orchardgrass ( Dactylis glomerata L.). Segments were plated at time periods ranging from 21 to 0·9 d (21 h) prior to launch on an 11 d spaceflight (STS-64). Using a paired t -test, there was no significant difference in embryogenesis from preplating periods of 14 d and 21 d. However, embryogenesis was reduced by 70% in segments plated 21 h before launch and this treatment was significant at P = 0·0001. The initial cell divisions leading to embryo formation would be taking place during flight in this treatment. A higher ratio of anticlinal:periclinal first cell divisions observed in the flight compared to the control tissue suggests that microgravity affects axis determination and embryo polarity at a very early stage. A similar reduction in zygotic embryogenesis would reduce seed formation and have important implications for long-term space flight or colonization where seeds would be needed either for direct consumption or to grow another generation of plants.     

Shigeo Yamanouchi (1876–1973): A noted Japanese phycologist

Dr Shigeo Yamanouchi was born in Yamagata Prefecture and completed his secondary education at Tokyo Higher Normal School (THNS) where he was also a professor until 1904. In 1905, he went to the University of Chicago in the USA and earned a PhD in Botany in 1907. He is best noted for his excellent research on the cytology and life histories of the marine algae Polysiphonia, Fucus, Cutleria, Aglaozonia and Zanardinia, published between 1906 and 1921 while he was associated with the University of Chicago. He also described the freshwater green alga Hydrodictyon africanum. In 1910, he returned to THNS as a Professor and wrote several botanical textbooks, receiving his DSc degree in 1911 and traveling in England and the USA as an advisor for the Japanese Ministry of Education during 1911–1913. For much of the time between 1920 and 1942 he remained in the USA, returning to Japan following the advent of World War II, During his later life, he was in obscurity, and sadly there is very little recorded of his activities in the post-war years. He died in Tokyo on 2 February 1973 at the age of 96.     

Regeneration of Cladrastis lutea (Fabaceae) via somatic embryogenesis

Summary Immature embryos from 5 Cladrastis lutea (Michx.) K. Koch (yellowwood) trees were initially cultured on modified Schenk and Hildebrandt medium (SH) containing either 4.5, 9.0, 13.5 or 23 M 2,4-D. One-third of the explants were transferred to SH medium supplemented with 25.0 M NAA after 2 and 3 weeks respectively. The remaining explants were incubated on the initial 2,4-D containing media for 6 weeks. Groups of somatic embryos formed directly only at the proximal end of cotyledons; only a few formed as single embryos. The greatest numbers were formed from zygotic embryos explanted from 6–8 weeks post-anthesis and initially cultured on medium containing 9 or 13 M 2,4-D. However, all treatments supported somatic embryogenesis. In the second year, explants were initially cultured on SH medium containing either 9.0, 13.5, or 23 M 2,4-D and then transferred to SH medium containing 4.0 M ABA after 2 or 3 weeks. ABA did not affect the development of somatic embryos. Six of 21 somatic embryos germinated on half-strength SH medium without growth regulators. Three entire plantlets were formed, but only one was established in soil.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - ABA abscisic acid - CRAF III chromium trioxide-acetic acidformalin     

Asexual reproduction,regeneration, and somatic embryogenesis in the planarian Dugesia tigrina (Turbellaria)

In reviewing recent research published in Russian on regeneration and asexual reproduction, the following morphogenetic processes in the planarian Dugesia tigrina are considered: 1) regeneration of lost parts of the body; 2) regeneration of the whole worm from fragments of the body, either by normal regeneration when the inital polarity of the fragment is retained or by somatic embryogenesis when one or more new axes of polarity arise; 3) somatic embryogenesis, or development of individuals from somatic cells; 4) hypermorphosis, or the presence of more than the usual number of organs or body parts, a process that can be interpreted in terms of somatic embryogenesis; and 5) asexual reproduction. Some morphological, biochemical, and physiological studies of the division zone in D. tigrina demonstrate peculiarities of a local breakdown of integrative functions, a breakdown which in turn causes division of the individual to take place at this zone; timing of division is controlled by the organism as an integrated whole.     

Recurrent somatic embryogenesis and development of somatic embryos in Akebia trifoliata (Thunb.) Koidz (Lardizabalaceae)

Plant Cell, Tissue and Organ Culture (PCTOC) - A simple and effective protocol was established for recurrent somatic embryogenesis and plant regeneration in Akebia trifoliata (Thunb.) Koidz....     

The Green sea turtle (Chelonia mydas): nesting on Ascension Island, 1973–1974

The collection of eggs of Chelonia mydas from beaches on Ascension Island and elsewhere for hatching at the Mariculture Ltd farm on Grand Cayman was described in a previous paper (Simon, 1975). Improved organization of these collections has made it possible to record many incidental observations which throw light on the nesting behaviour and performance of the female Chelonia , and Ascension Island, because of its small size, numerous beaches and good communications, proved to be particularly favourable for such research. The present paper records observations made in February and March 1973 and 1974. The second author has contributed only by the analysis of the data and the preparation of the paper.