Moderate abiotic stresses increase rhizome growth and outgrowth of axillary buds in Alstroemeria cultured in vitro.

Alstroemeria is multiplied in vitro by forced outgrowth of lateral rhizomes from rhizome explants. The multiplication rate is very low because of strong apical dominance and poor rhizome growth. We report here that moderate abiotic stresses stimulate both rhizome growth and outgrowth of lateral rhizomes, and accordingly increase multiplication. Rhizome explants were exposed to heat by a hot-water treatment (HWT) or by a hot-air treatment. Both increased rhizome growth when applied for 1 or 2 h in the range of 30-40 °C. The maximal enhancement was 75 %. Other abiotic stresses were also examined. Cold (0 °C) and partial anaerobiosis increased rhizome growth significantly. The increases brought about by drought and salinity were not statistically significant. Because underground storage tissues like rhizomes are adaptations to survive climatic stresses, we presume that the increased sink-strength of rhizomes induced by moderate stress is related to stress adaptation. Moderate heat stress (38 °C HWT, 1 h) also resulted in protection of Alstroemeria plantlets from severe heat stress (45 °C HWT, 1-2 h) a few hours after the moderate stress. All abiotic stresses also increased the outgrowth of lateral rhizomes. [ABSTRACT FROM AUTHOR]