EFFECT OF TEMPERATURE ON ROOTS AND SHOOTS FORMATION IN THREE VANILLA SPECIES (ORCHIDACEAE) UNDER CONTROLLED CONDITIONS

Abstract

Background. Vanilla planifolia is a species of commercial and cultural importance. However, its growth and development could be affected by the increase in temperature caused by climate change. In contrast, V. pompona and V. insignis are wild species with potential use as aromatic species and they show greater tolerance to prolonged exposure to high temperatures. Objective. To determine the effect of temperature on the development of roots and shoots of V. planifolia, V. pompona and V. insignis under controlled conditions. Methodology. Cuttings of approximately 20 cm with two nodes were grown at 25, 32, 35 and 38 °C under controlled conditions, with a relative humidity of 100%, for six weeks. To evaluate cutting development, the number of roots produced was recorded, as well their length, their growth rate and their diameter. Likewise, the number of shoots generated, their length, growth rate and diameter were also counted. The experimental design was completely random, and the data were analyzed using Tukey post hoc analysis of variance (P < 0.05). Results. The increase in temperature affected the promotion and root growth in V. planifolia, which showed the greatest length at 25 °C (20.64 ± 0.26 cm) and the lowest value at 35 °C (1.22 ± 0.49 cm), contrary to V. insignis, where the increase in temperature at 35 °C favored root elongation (4.76 ± 0.07 cm), while the lowest growth was observed at 25 °C (1.74 ± 0.13 cm). V. pompona did not present significant differences in root growth at the three temperatures evaluated. Similarly, the increase in temperature showed a distinct influence on the promotion and growth of the shoot. V. planifolia only produced shoots at 32 °C (8.4 ± 0.4 cm) and V. pompona generated them at 32 and 35 °C, being those of greater length at 35 °C (3.3±0.13 cm) and did not produce at 25 °C; while V. insignis showed the highest shoot growth at 25 °C (7.22 ± 0.2 cm) and the lowest at 32 °C (6.56 ± 0.12). At 38 °C, 100% mortality was observed in the three species. Implications. The growth of roots and shoots of V. planifolia are affected by an increase in temperature above 32 °C, therefore, conservation and genetic improvement programs are needed that could start from the qualities that V. pompona and V. insignis showed. Conclusion. Temperature ranges between 25 and 35 °C have a differential effect on the promotion and growth of roots and shoots for the species V. planifolia, V. insignis and V. pompona.