| heal.abstract |
The effect of light on the induction, development and maturation of somatic embryos from cultures of various species, after prolonged incubation for in vitro conservation purposes, was investigated. Cotyledonal and leaf explants of pepper (Capsicum annum L.), squash (Cucurbita pepo L.), melon (Cucumis melo L.), gardenia (Gardenia jasminoides L.) and rose (Rosa hybrida L.) were cultured on a solid Murashige and Skoog (MS) medium supplemented with various plant growth regulators for the induction of callus and somatic embryos. Cultures were incubated for 6-14 weeks either (i) continuously in the darkness, (ii) first in the darkness for 1-10 weeks and then under light (16 light/8 dark photoperiod) or (iii) continuously under illumination. In order to investigate the effect of light intensity, cultures were incubated under photo synthetic photon flux densities (PPFDs) of 50 to 250 μmol m-2 s-1. The results indicated that both the intensity of light as well the duration of incubation under illumination or in the darkness significantly affected somatic embryo induction and development. Significantly more somatic proembryos and globular embryos were induced when cultures were initially incubated in the darkness or under a low PPFD. The optimal duration of the preincubation period in the darkness varied among different species. Further embryo development to the torpedo-shape stage and embryo maturation was significantly affected by the exposure of the cultures to light during the induction phase. |
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