The effect of long term hot and cold environments in flower development

Laboratory studies of cold and heat stress traditionally performed short time experiments identifying the early players in plant adaptation to changes in temperature. However, long term experiments of low or high temperatures under lab conditions are practically inexistent. To address this gap, we grew snapdragon plants from two-week-old till maturity under normal (22/16 °C), cold (15/5 °C), and hot (30/23 °C) conditions for a period of two years. Floral size, anthocyanin content and pollen viability had higher values in cold, decreasing in middle and high temperatures. Chlorophyll content was higher in cold and stable in control and hot temperatures, while pedicel length increased under heat. Normal conditions were optimal for scent emission and seed production. Scent complexity increased with temperature. Transcriptomic analysis of mature flowers followed by gene enrichment analysis showed changes in genes supporting the affected traits. Unexpected programs included hypoxia, unsaturated fatty acid metabolism, ribosome structure, carboxylic acid, sugar and organic ion transport or protein folding. We found differential expression of meristem identity and B function genes but not C function, supporting the floral size data. Prolonged heat or cold, causes pleiotropic adaptations in ribosomal and membrane structures. Pollinator-related traits like scent and colour follow opposite trends indicating an equilibrium to render attractive organs for pollination.