View/Open - ResearchSpace - University of KwaZulu-Natal
View/Open - ResearchSpace - University of KwaZulu-Natal
View/Open - ResearchSpace - University of KwaZulu-Natal
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In vitro culture initiation and multiplication<br />
camerooniana and R. rosea (no in vitro response was observed for these species),<br />
can be used as a faster method for obtaining shoot cultures. The germination <strong>of</strong> the<br />
embryos <strong>of</strong> these species does not require the low temperature and stratification<br />
treatments that the seeds need as germination cues and the embryo geminates<br />
within about 2 weeks, whereas seeds require at least 2 months.<br />
Although a higher percentage <strong>of</strong> R. leipoldtii hypocotyls than embryos showed some<br />
growth response because <strong>of</strong> their larger size, embryos were more responsive to the<br />
plant growth regulators in the medium because <strong>of</strong> the younger physiological age <strong>of</strong><br />
these tissues (SMITH, 2000).<br />
Although the rooting <strong>of</strong> embryo-derived shoots <strong>of</strong> R. leipoldtii was inhibited by high<br />
concentrations <strong>of</strong> cytokinins and developed more callus compared to hypocotyl-<br />
derived shoots it should be considered that the hypocotyls are essentially fully<br />
developed plants with trimmed shoots and roots, so that the development <strong>of</strong> an entire<br />
new shoot is not necessary. Following this logic, it also means the single shoots<br />
observed in some cultures for which hypocotyls is the initial explant was in fact the<br />
original hypocotyl, which did not form more shoots but only elongated and, in most<br />
cases, produced roots. When the data is viewed from this perspective, embryos<br />
produced more shoots than hypocotyls.<br />
These factors make the choice <strong>of</strong> explant type very difficult. The explant type used<br />
should therefore rather depend on the species used.<br />
These results show that the species response in Romulea is influenced to great<br />
extent by genetic factors, as media treatments or explant type could not increase the<br />
shooting <strong>of</strong> R. diversiformis, R. minutiflora and R. monadelpha to numbers similar to<br />
that <strong>of</strong> R. flava and R. sabulosa and the rooting <strong>of</strong> some species is not suppressed<br />
by a medium with a high kinetin concentration while the rooting <strong>of</strong> other species is<br />
inhibited on such a medium.<br />
Although the kinetin concentrations tested in the R. sabulosa shoot multiplication<br />
experiment was not the same as those used in previous experiments, the number <strong>of</strong><br />
shoots produced after two months on a medium supplemented with 2.5 µM mTR (5.5<br />
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