Acclimation of Young Plants of Opuntia spp. to the Heightened Night Temperature

Increases in global temperatures, due to the climate change, are generating stress in most plant species. We hypothesize that young plants of Opuntia spp. adjust their Crassulacean acid metabolism (CAM) to the increase in nighttime temperature, allowing them to continue growing. The study was carried out in a greenhouse and laboratory of the Colegio de Postgraduados, Montecillo, Mexico. Three-month-old greenhouse-grown plants remained in a control environment with an average day/night temperature of 19.1/12.3 °C or were maintained in a chamber with increased nighttime temperatures averaging 19.1/18.9 °C day/night for 70 days. The experimental design was completely randomized with two treatments (control and high nighttime temperatures). After 70 days of high nighttime temperatures (HNT), at dawn (end of CAM phase I), plants had a 45% decrease in glucose (2.9 to 1.5 mg/100 mg dry tissue; dt) concentration and doubled and tripled fructose (0.43 to 0.95 mg/100 mg dt) and sucrose (0.47 to 0.09 mg/100 mg dt) concentrations. Glucose consumption may be related to the plant’s metabolic energy expenditure to overcome stress. The significant increase in fructose and sucrose is explainable by their function as signaling molecules among others. In contrast, photosynthetic efficiency, i.e., increased compared to the control, but the difference of acidity (end of phase I less phase III), the concentration of starch (1 mg/100 mg dt), free amino acids and soluble protein (1.2 mg/100 mg dt), wet and dry matter, stem height (60 cm) and width of the stem at dawn were not significantly affected. The adjustments in C and N metabolism and the non-significant effect on growth promoted by 70 HNT days may be related to adjustments in enzyme activities without changes in protein concentration. Young Opuntia spp. plants adjust their metabolism in response to increased nighttime temperatures, allowing them to maintain growth similar to that of the control. The results confirm the great potential of using the Opuntia genus in agriculture and genetic improvement in the face of the challenges posed by climatic change.