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In Alstroemeria, micropropagation is achieved by axillary bud outgrowth. However, the multiplication rate is rather low (1.2–2.0 per cycle of 4 weeks) due to strong apical dominance. Even though several factors (i.e. culture media, growth regulators, and environmental conditions) have been studied, no significant improvements have been achieved. Basic research on apical dominance mechanism in Alstroemeria is therefore required. This may enhance the understanding how apical dominance controls axillary bud outgrowth in this plant and others. A second drawback in micropropagation of Alstroemeria is the slow growth of rhizomes. In this respect mineral nutrition and the effect of stress are significant. The former is implicated in storage organ growth to literature studies, in particular phosphate. The latter, the effect of stress, is based on observations of growers who noticed a strong increase of rhizome growth after moderate abiotic stress. This research deals with the backgrounds of growth of Alstroemeria in vitro. It deals with (1) the regulation of apical dominance, (2) the growth of rhizomes by applying abiotic stress and (3) the growth of rhizomes by adapting the formulation of inorganic nutrients. Alstroemeria is characterized by strong apical dominance. We observed that the outgrowth of axillary buds is inhibited byboth rhizome and aerial shoot tips. The hormonal regulation is like the regulation in model plants (Arabidopsis, pea, petunia) involving as promoting hormone cytokinin and as inhibiting ones auxin and the carotenoid-derived hormones namely strigolactones (SLs). The involvement of SLs is examined in more detail. Fluridone, an inhibitor of SL synthesis, promotes the outgrowth of lateral rhizomes. It is supposed that SLs act by inhibiting auxin transport. Our experiment to measure auxin transport seem to agree with this. We also found that the auxin transport inhibitors TIBA and NPA reverse the effect of fluridone. The moderate heat stress, and also cold stress and anaerobic stress strongly promote rhizome growth. The increase of growth is not reduced by stress-protective treatments. Therefore, we conclude provisionally that this phenomenon is itself a response of plantlets to protect them from future adverse conditions. Alstroemeria explants rapidly consume organics and inorganics from the nutrient medium but so far no relationship could be established with poor growth. There are marked differences with respect to mineral composition of the rhizome and the aerial shoot for Ca, P and Mg.

In Alstroemeria, micropropagation is achieved by axillary bud outgrowth. However, the multiplication rate is rather low (1.2–2.0 per cycle of 4 weeks) due to strong apical dominance. Even though several factors (i.e. culture media, growth regulators, and environmental conditions) have been studied, no significant improvements have been achieved. Basic research on apical dominance mechanism in Alstroemeria is therefore required. This may enhance the understanding how apical dominance controls axillary bud outgrowth in this plant and others. A second drawback in micropropagation of Alstroemeria is the slow growth of rhizomes. In this respect mineral nutrition and the effect of stress are significant. The former is implicated in storage organ growth to literature studies, in particular phosphate. The latter, the effect of stress, is based on observations of growers who noticed a strong increase of rhizome growth after moderate abiotic stress. This research deals with the backgrounds of growth of Alstroemeria in vitro. It deals with (1) the regulation of apical dominance, (2) the growth of rhizomes by applying abiotic stress and (3) the growth of rhizomes by adapting the formulation of inorganic nutrients. Alstroemeria is characterized by strong apical dominance. We observed that the outgrowth of axillary buds is inhibited byboth rhizome and aerial shoot tips. The hormonal regulation is like the regulation in model plants (Arabidopsis, pea, petunia) involving as promoting hormone cytokinin and as inhibiting ones auxin and the carotenoid-derived hormones namely strigolactones (SLs). The involvement of SLs is examined in more detail. Fluridone, an inhibitor of SL synthesis, promotes the outgrowth of lateral rhizomes. It is supposed that SLs act by inhibiting auxin transport. Our experiment to measure auxin transport seem to agree with this. We also found that the auxin transport inhibitors TIBA and NPA reverse the effect of fluridone. The moderate heat stress, and also cold stress and anaerobic stress strongly promote rhizome growth. The increase of growth is not reduced by stress-protective treatments. Therefore, we conclude provisionally that this phenomenon is itself a response of plantlets to protect them from future adverse conditions. Alstroemeria explants rapidly consume organics and inorganics from the nutrient medium but so far no relationship could be established with poor growth. There are marked differences with respect to mineral composition of the rhizome and the aerial shoot for Ca, P and Mg.

An optimalized method of micropropagation of Douglas fir is described. Seasonal changes were found in optima for nitrate and sucrose in the medium and in the optimum for the light intensity during the culture of shoot initials. Differences in morphogenesis were obtained from shoot initials that had been isolated from buds in 10 topophysical positions on 2-year-old trees. These differences between the shoots were influenced by the medium, the light intensity, and by forcing or topping the mother trees or treating them with growth regulators. Shoots from each of the topophysical positions had a characteristic photosynthesis. A first attempt is made to compare in vivo flushing with the morphogenesis of shoot initials in vitro.

An optimalized method of micropropagation of Douglas fir is described. Seasonal changes were found in optima for nitrate and sucrose in the medium and in the optimum for the light intensity during the culture of shoot initials. Differences in morphogenesis were obtained from shoot initials that had been isolated from buds in 10 topophysical positions on 2-year-old trees. These differences between the shoots were influenced by the medium, the light intensity, and by forcing or topping the mother trees or treating them with growth regulators. Shoots from each of the topophysical positions had a characteristic photosynthesis. A first attempt is made to compare in vivo flushing with the morphogenesis of shoot initials in vitro.