adventitious regeneration

adventitious regeneration - Chapter 10 Adventitious...

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Chapter 10 Adventitious Regeneration 1. INTRODUCTION New organs such as shoots, roots or embryos can be induced to form on plant tissues lacking pre- existing meristems. Such freshly originated organs are said to be adventive or adventitious. The creation of new form and organisation, where previously it was absent, is termed adventitious organogenesis, or, in the case of embryo-formation, somatic embryogenesis. Adventitious formation of shoots is referred to as caulogenesis and of roots as rhizogenesis . From explants, structures may be formed that are similar to the embryos found in true seeds. Such embryos often develop a region equivalent to the suspensor of zygotic embryos and, unlike shoot or root buds, come to have both a shoot and a root pole. To distinguish them from zygotic or seed embryos, embryos produced from cells or tissues of the plant body are called somatic embryos and the process leading to their inception is termed somatic embryogenesis (see Chapter 9). The word ‘embryoid’ has been especially used when it has been unclear whether the embryo-like structures seen in cultures were truly the somatic equivalent of zygotic embryos. Somatic embryogenesis is now such a widely observed and documented event that somatic embryo has become the preferred term. The formation of leaves adventitiously in vitro usually denotes the presence of a shoot meristem. Sometimes leaves appear without apparent shoot formation: opinions are divided on whether such leaves can have arisen themselves de novo , or whether a shoot meristem must have been present first of all and subsequently failed to develop. An example is regeneration from flower-stem explants in tulip (Kuipers and Langens-Gerrits, 1997). The formation of flowers or floral parts is rare, occurring only under special circumstances. They are formed from, e.g., flower stem tissues (Van Den Ende et al., 1984a,b). This type of regeneration is not relevant to plant propagation. Caulogenesis, rhizogenesis and somatic embryogenesis are essential for plant multiplication in vitro . New plants are seldom obtained in culture by the union of shoots and roots independently formed in callus. The production of complete plantlets by adventitious regeneration is achieved from adventitious shoots, which are subsequently rooted, or from somatic embryos. Shoots, roots and somatic embryos arise from single cells, or groups of cells, which become induced by the cultural conditions to become centres of active cell division (adventitious meristems), each capable of producing an organ of the one kind. Regeneration has now been observed in vitro in numerous plants of many genera, but it cannot yet be induced universally. Even within a single species, varieties can be found, which are recalcitrant. Moreover, the capacity for regeneration can be lost
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This note was uploaded on 07/23/2011 for the course HOS 6737c taught by Professor Moore during the Spring '09 term at University of Florida.

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adventitious regeneration - Chapter 10 Adventitious...

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