Sources of morphological non-uniformity in gentian propagated in vitro without plant growth regulators
2016
Keshavarzi, M. | Woolley, D. J. | Heyes, J. A. | Funnell, K. A.
To be economically valuable as a potted plant it is desirable for gentians to produce uniform plants with multiple branches (secondary shoots) at flowering. Not all propagules of the cultivar 'Little Pinkie' grew equally when propagated in vitro from either a single node explant, or just the apical region of the donor plant in vitro. Explants from the tip position produced a single primary shoot derived from the continued morphological development of the apex and no secondary shoots. In contrast, explants from lower positions produced between 0 and 8 secondary shoots. The number of shoots and total weight of the in vitro plantlets increased up to three- and two-fold, respectively, with increased distance of the explant position from the tip. In addition, with increased distance from the tip, morphological non-uniformity increased for all growth variables. Scanning electron microscopy evidenced the formation of additional vegetative buds (adventitious), especially for explants taken toward the base of the original shoot. However, in spite of the increase in number of secondary shoots raised on the explants taken from lower down the stem, the total number of usable explants was the same for plantlets derived from all positions. The physiological mechanisms and underlying hormonal control will be discussed together with strategies to increase the number of usable explants.
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