Abstract

Among the pragmatic approaches to addressing the issue of climate change is reduction of its anthropogenic causes (such as emissions from burning of fossil fuels and indiscriminate removal of vegetation cover) and making of conscious efforts toward increasing global vegetation cover. Based on the desirable qualities of afforestation species, this study aimed to quantify the rate of leaf transpiration in seven selected tree species in Ogbomoso Nigeria, with a view to ascertaining their suitability for afforestation of water stress habitats. The mean quantity of water transpired per cm2 area of ten randomly selected mature leaves of seven tree species from the study location (80 10' 12.217''N, 40 15'12.607''E - 80 9' 45.834''N, 40 16' 6.209''E) was determined as a difference in the weight of a 4cm2 dry cobalt chloride paper (DCCP) and wet cobalt chloride paper stuck to adaxial/upper and abaxial/lower leaf surfaces until the blue DCCP completely turned to pink, and the time taken for this to happen was recorded. The rate of transpiration was also calculated in mg/cm2/min of each leaf surface by dividing the amount of water transpired/cm2 area by the respective time taken, and the means for the seven tree species were obtained. Higher mean rates of water transpiration in mg/cm2/min were recorded on the abaxial (18.6±2.4 – 30.6±1.8 in Psidium guajava and Ficus exasperata respectively) than the adaxial (14.4±1.8 – 25.2±6.0, also in P. guajava and F. exasperata) leaf surfaces. Evidence from the statistical analysis led to the conclusion that F. umbellata and F. exasperata are better atmospheric humidifiers than the other five tree species studied which instead, are better water conservers. The rate of leaf transpiration in four of the latter namely; Anacardium occidentale, F. benjamina, Mangifera indica and P. guajava are on a par with the fifth i.e. Azadirachta indica, the widely acclaimed afforestation species of dry lands. Therefore, the seven tree species studied are suitable candidates for afforestation of dry areas, the two humidifiers where increased atmospheric water vapour is desired, and the water conservers for water-stress environments.