Evapotranspiration of Pineapple in Hawaii

The plants of the cerra(lo and caatinga ecological provinces of Brazil, the suggested original home of pineapple (3), have many and varied mechanisms whereby they have adapted to the frequent development of moisture stress.The pineapple planit presenits a peculiarly interestinig combination of those traits that have been l)ropose(l for xerophytic and sc!ero- phyllous plants (10, 15).Preferential collapse of the wvater storage tissue of the leaf in time of mois- ture stress is further evidence of the ilntriguing adaptation of the pineapple p)lant to water (leficit (15. 19).Reduction in the daytime rate of v-apor exchange from the pineapple leaf (14) could well be ac- complished bv the highly cutinized upper epidermis and the deeply entrenched stomatal pores with an overlying mat of trichomes on the undersurface.The very lowN rate of but 0.3 to 0.5 niig of water lost per Cm112 of leaf surface in anl houtr conitrasts sharply with the 26 mg from a corn leaf, and the 43 mg from a cocklebur leaf (23).Such restricted daytime gas exchange through the leaf requires some compensatory mechanism for a CO., supply for photosynthesis.The acid metabolism of crassulacean plants has been shown to provide such a miiechainisml, and it has been reported specifically for l)ineapple (21. 22).