PHYSIOLOGICAL AND ANATOMICAL ADAPTATIONS BY YOUNG ASTROCARYUM-JAUARI MART (ARECACEAE) IN PERIODICALLY INUNDATED BIOTOPES OF CENTRAL AMAZONIA

Young plants of the palm, Astrocaryum jauari, are well-adapted anatomi cally and physiologically to hypoxic conditions. Annual inundation for as long as 300 days, at water temperatures of 28-degrees-C, produce n either leaf loss nor rotting of the roots. At a depth of 1.2 m beneath blackwaters, the leaves in the crowns of the plants show little decre ase in the amount of chlorophyll. In contrast, submersion to an equal depth in whitewater produces a loss of chlorophyll. Photosynthetic oxy gen production decreases to less than 30 percent of the terrestrial ra te in plants submerged beneath blackwater, and to less than 10 percent in plants submerged in whitewater. Ethanol production compensates for temporary energy deficits. Respiration by the roots is greatly reduce d but does not cease during inundation. Well-developed aerenchyma perm its gas transport from the branches to the roots. A cylinder of stone cells and sclerenchyma fibers in the outer periphery of the primary ba rk prevents the collapse of the root aerenchyma due to reduced pressur e within the roots and increasing external pressure as water depth ris es.