Impact of Exposure to Low Temperature Degrees in Field Conditions on Leaf Pigments and Chlorophyll Fluorescence in Leaves of Mango Trees

Abstract

This experiment was conducted to found the connection between low temperature stress in vivo conditions (ambient-air temperature) and the changes in some physiological and biochemical events (leaf pigments and chlorophyll fluorescence) of mango trees in response to exposure to natural low temperature (cold). To verify this objective, 12 popular commonly mango cultivars (25 years old) which grown in private orchard in Fayoum Governorate, Egypt were selected for this study which carried out during the period from November to March of years; 2012 and 2013. The selected cultivars were: Alphonso, Baladi, Bullock's Heart, Helmand, Hindi Besennara, Mabrouka, Mestekawy, Nabeeh, Oweisi, Spates, Taimour and Zebda. Based on the obtained results, it can be stated that, chlorophyll (a) concentration in the leaves was significantly differed among the cultivars throughout the whole sampling times, in this respect, Helmand one gave the highest one while, and the highest one by sampling times was November one. The concentration of chlorophyll (b) was significant as effected by the effect of cultivars and sampling time recorded the highest value by the cultivar of Spates and December sample, respectively. Total chlorophyll concentration in the leaves reached its peak by the cultivar of Nabeeh and sampling time of December as compared to others. The both of Ewais cultivar and the sample of March showed the highest values of carotenoids concentration in the leaves. The levels of anthocyanin in leaves were significantly differed as affected by the cultivars and sampling times, indicating that the cultivar of Helmand and November sample recorded the highest values of anthocyanin in leaves. The greatest reductions in Fv/Fmratio were recorded at month of November and indicated that the reductions were in the order of Alphonso˃ Mabrouka˃Taimour˃ others. The effect of sampling time, cultivars and their interaction on Fv/Fm were significant, but small between some values of Fv/Fm.