XVI International Botanical Congess

To test the hypothesis that development and hydraulic conductivity vary along roots in response to moisture, desert agaves were grown in containers with drying proximal and distal compartments and moist middle compartments. Root regions from middle compartments had less sclerenchyma, fewer suberized cells, and greater hydraulic conductivity than did root regions from distal compartments. Proximal regions, particularly of roots generated during soil drying, had highly conductive zones near the plant base with few layers of sclerenchyma, many endodermal passage cells, and several unlignified vessels, suggesting that moisture from the shoot influences root development. The effects of mercuric chloride on hydraulic conductivity suggested that aquaporin activity along a root also depended on moisture and on the developmental state of root tissues.