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1. Changes in chloroplast ultrastructure, fatty acid components of thylakoid membrane and chlorophyll a fluorescence transient in flag leaves of a super-high-yield hybrid rice and its parents during the reproductive stage | |||
Mei-Ping Zhang,Guo-Xiang Chen | |||
Biology 14 January 2010 | |||
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Abstract:In plants, it is well established that chloroplast is one of the early targgeted organelles to break down during leaves senescing. Here we applied a newly-developed super-high-yield hybrid rice (Oryza sativa L.) LiangYouPeiJiu (LYPJ) and its parents lines to investigate changes in ultrastructure of chloroplasts, fatty acid composition of thylakoid membrane lipids and chlorophyll a fluorescence transient in natural senescing leaves. We found that at full expansion of flag leaves in three lines, chloroplasts often showed oblong shapes with a typical membrane system of stroma and grana thylakoids, whereas their shapes had been changed from oblong to spherical during senescence. Our data showed that the initiation of senescence displayed accumulation of starch and an increase in the number and size of plastoglobuli with the damaged thylakoid membranes; subsequently, swollen thylakoid membranes in stroma and in grana with a significant increase in MDA content, and disorganization of thylakoid membrane system with significant changes in fatty acid composition of thylakoid membrane lipids were developed. Compared with its parents, the newly-developed hybrid rice LYPJ had the highest capacity of carbohydrate transport from leaves (sources) to ears (sink), the lowest accumulation of starch grains in the leaf chloroplasts, and the slowest senescing rate of chloroplast in overall leaf senescence process. Chlorophyll a fluorescence transients of three kinds of flag leaves were analysed by so-called JIP-test. The results of analysis suggest that these findings inculding a high inherited activity of antioxidant enzymes and high photosynthetate transport to pretect chloroplast structure in the hybrid rice LYPJ have close relations to its super-high yield . | |||
TO cite this article:Mei-Ping Zhang,Guo-Xiang Chen. Changes in chloroplast ultrastructure, fatty acid components of thylakoid membrane and chlorophyll a fluorescence transient in flag leaves of a super-high-yield hybrid rice and its parents during the reproductive stage[OL].[14 January 2010] http://en.paper.edu.cn/en_releasepaper/content/38983 |
2. A Fibre-Assembling-Pressure Model for Developing Root Pressure | |||
Wang Xiaoen | |||
Biology 12 December 2008 | |||
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Abstract:For decades, it has well been known that the drive force of conducting both water and dissolved mineral ions from roots to leaves of plants makes mainly up of two: the pull of transpiration from leaves and root pressure. It had early been clear with regard to the transpiring pull, but mechanisms how root pressure be developed, hitherto, is fuzzy. Based on both experimental phenomenon of siphon-like transport of water defying gravity along fibre surface and crystallisation mechanisms, this paper theoretically suggests a fibre-assembling-pressure model for developing root pressure. According to the model, in roots the continuous polymerization of fiberized network, such as formation of nascent cell wall and maturity of xylem, can develop the fibre-assembling pressure, a positive hydraulic pressure. For a plant that grows with vigor, growth of all of fibres, such as xylem, can provide a drive force for water transport, division and expansion of cells in meristems, and gravitropic growth of roots. | |||
TO cite this article:Wang Xiaoen . A Fibre-Assembling-Pressure Model for Developing Root Pressure [OL].[12 December 2008] http://en.paper.edu.cn/en_releasepaper/content/26564 |
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