Is the frequency of apomeiosis in the Rhodophyta a genetic character?
The small rhodophyte Antithamnionella sarniensis Lyle (Ceramiaceae), a very common species on the Atlantic coast of France, has a normal Polysiphonia-like life cycle (Sundene, 1964), but some tetraspores can give new tetrasporophytes directly (L'Hardy-Halos, 1985). This phenomenon has now been studied in detail (Magne, 1986). Twenty strains were prepared starting from sterile plants collected in various places along three hundred kilometers of shoreline. The strains were kept in stock cultures at a low temperature (14 C) with dim natural light and were propagated only by cutting. Exceptionally, one of these strains originated from an apomeiotic tetraspore, and another one is the original strain of von Stosch (1969), who kindly provided it. All the strains proved to be tetrasporophytic, in accordance with the dominance of tetrasporophytes in the field. The progenies of the different strains have been investigated. For each, material from the stock culture was cultivated in monitored conditions (20°C with cool white light of 20 tE.-m-2.s 1, 12 h.d ') to produce tetraspores. Plantlets issuing from the spore-sets were picked randomly, individually transferred in small glass jars and cultivated until reproductive organs were formed; one hundred plantlets were used of each strain. In numerous strains, the progeny is a mixture of gametophytes and tetrasporophytes; the proportions of tetrasporophytes differ from one strain to another over a range from 0% to 100% and show many intermediate values (Magne, 1986). It can be sup-
Seasonal occurrence and reproduction of Hypnea charoides (Rhodophyta) in Tung Ping Chau, N.T., Hong Kong SAR, China
Seasonal occurrence and reproduction in populations of Hypnea charoides Lamouroux were investigated along two coastal shores, A Ma Wan and Lung Lok Shui, in Tung Ping Chau, N. T., Hong Kong SAR, China, from 1996 to 1999. Annual growth of these populations was initiated in early winter (November–December) and ended in late spring (April–May). Mean length of H. charoides in A Ma Wan was significantly negatively correlated with photoperiod (r=−0.359, n=38, p<0.05) and seawater temperature (r=−0.669, n=38, p<0.05). Vegetative plants were dominant but relatively high abundance in tetrasporic plants was observed at the end of each growing season. Percentage occurrence of tetrasporic plants was significantly positively correlated with seawater temperature in samples collected at −1 m CD (r=0.635, n=19, p<0.05), −2 m CD (r=0.690, n=13, p<0.05) and from drifted populations (r=0.705, n=17, p<0.05), suggesting that increase in seawater temperature might induce tetrasporogenesis of H. charoides in A Ma Wan. Plants in Lung Lok Shui were mostly vegetative but 100% tetrasporic samples were collected at −1 m CD during an unusual growth period in October 1998. High abundance of tetrasporic plants was also observed at a depth of −10 m CD on 9 April 1998 (97.5%) and 22-April 1999 (90%). Significantly negative correlation was found in percentage occurrence of vegetative plants at −10 m CD with photoperiod (r=−0.553, n=14, p<0.05) and seawater temperature (r=−0.855, n=8, p<0.05). Dominance of vegetative and tetrasporic plants and rarity of cystocarpic plants in both A Ma Wan and Lung Lok Shui suggested that the life span of H. charoides might be very short and/or majority of the plants underwent apomeiosis to complete their life cycles in Tung Ping Chau.
Complexity, Network-Decisions And Alternative Risk Premia: Some New Theories Of Structural Change And Portfolio Decisions.
Structural Change is the basis for many decisions such as government fiscal and monetary policies, government interventions, corporate-expenditure decisions, corporate strategic decisions, portfolio management decisions in finance; household allocation decisions, etc.. Structural change in industries and national economies is increasingly more difficult to detect partly because of the growth and dominance of Complex Systems and “Networks” in modern industries and economies – such Networks and Complex Systems include GVCs (global value chains), retail store networks; franchising networks; internet networks; services networks; credit-chains in industries; online social networks; etc.. The relationship between Complexity and Structural Change is well established in the physics, applied math and economic dynamics literatures. Traditional definitions and modeling of structural change have erroneously focused on changes in labor, technological progress, market share, and or capital – which are grossly inadequate in the new economy and post- global financial crisis (as confirmed by changes in the global retailing and housing industries and other industries). Also the modeling of structural change seems to be constrained by the availability of data, and often omits the relationship between structural change on one hand, and globalization, financial stability and international financial contagion. This article: i) introduces the Operations Strategy Model of structural change, explains how it differs from the Lewis Model of Structural Change; and explains the often omitted relationship between operations strategy (of companies and government agencies) and structural change; ii) introduces other new Complexity-based models/theories of Structural Change in industries; iii) reviews the relationships among Operations Research, Complexity and Structural Change; iv) explains the symbiotic relationship between structural change on one hand, and economic growth, financial stability, financial contagion and globalization; v) discusses the significant gap between academic research and practice and explains some issues and factors that should be considered in the development and testing of structural change models; vi) explains how alternative risk premia can be generated from new models of Structural Change.