MORPHOLOGICAL AND ANATOMICAL RESPONSES OF LYTHRUM-SALICARIA L (PURPLE-LOOSESTRIFE) TO AN IMPOSED WATER GRADIENT

Morphological and anatomical responses of Lythrum salicaria L. to an i mposed water gradient were assessed under greenhouse conditions. Nine- week-old seedlings were exposed to three levels of water availability for an 8-wk period. Fresh and dry mass of the shoot, root, and entire plant, shoot fresh:dry mass ratios, root:shoot fresh mass ratios, and root:shoot dry mass ratios were not significantly affected by water av ailability. Total fresh:dry mass ratios were significantly lower in th e dry treatment compared with the wet, while root fresh:dry mass ratio s were significantly greater in the intermediate and wet treatments. T otal stem diameter and porosity was generally higher in submersed port ions of hooded stems and roots, while tissue density was generally low er under these conditions. Stem diameter excluding the phellem did not differ among treatments. The total root diameter to diameter excludin g phellem showed significant increases with increasing water availabil ity. Adventitious and lateral roots in primary growth from all plants possessed an endodermis with Casparian bands and subsequently suberin lamellae and a modified, uniseriate hypodermis. Submerged stems and ro ots in secondary growth possessed a multilayered, lacunate polyderm, w hile nonsubmerged stems and roots had a compact, multilayered polyderm . Fluorescent properties of walls of some cells in the root and stem p olyderm indicate that these cells share features with endodermal cells .