Effect of High Temperature on Different Genotypes of Citrus

Abstract

Global warming as a result of greenhouse gases can have a detrimental effect on crop productivity. High temperature can be deleterious to the growth and development of citrus trees. In the present investigation, ‘Marsh’ grapefruit and ‘Hamlin’ sweet orange trees were exposed to a temperature 38 °C (100 °F) to explore the mechanism of high temperature tolerance in these two genotypes. Trees were grown in 15 × 8 cm plastic pots containing Fafard Mix 4P. Mineral nutrition was provided periodically using Peters’ professional fertilizer. Trees were kept at 700 µmole·m–2·s–1PARwith a 12-h light and 12-h dark photoperiod in environmental growth chambers and acclimated for 90 days at 23 to 27 °C (73 to 80 °F) before applying high temperature treatments. The experiment was conducted as a randomized complete-block design and mean values per plant were determined and subjected to analysis of variance. Plants were exposed to 38 °C (100 °F) for 10 days. Heat-induced oxidative stress was more pronounced in ‘Hamlin’ leaves than in grapefruit leaves in terms of H2O 2production. However, concentrations of H2O2 were same in both the genotypes in control conditions. Grapefruit leaves displayed a better antioxidant defense system under high temperature regimes than ‘Hamlin’ leaves. It seems ‘Hamlin’ sweet orange leaves will be more susceptible to rising global temperatures than grapefruit leaves.