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 anatomically and physiologically to hypoxic conditions. Annual inundation for as long as 300 days, at water temperatures of 28⚬C, produce neither 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 decrease in the amount of chlorophyll. In contrast, submersion to an equal depth in whitewater produces a loss of chlorophyll. Photosynthetic oxygen production decreases to less than 30 percent of the terrestrial rate 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 reduced but does not cease during inundation. Well-developed aerenchyma permits gas transport from the branches to the roots. A cylinder of stone cells and sclerenchyma fibers in the outer periphery of the primary bark prevents the collapse of the root aerenchyma due to reduced pressure within the roots and increasing external pressure as water depth rises.