MORPHOLOGICAL PLASTICITY OF THE CLONAL HERB LAMIASTRUM-GALEOBDOLON (L) EHREND AND POLATSCHEK IN RESPONSE TO PARTIAL SHADING

The present experiment investigates the morphological plasticity of La miastrum galeobdolon (L.) Ehrend. & Polatschek in response to light pa tchiness. In a garden experiment, stolons of the plant were grown unde r the following six light regimes: high light, low light, from low lig ht to high light, from high light to low light, under high light but w ith the apical region of the stolon under low light, and under low lig ht but with the apical region under high light. The low-light conditio ns provided 50 % of high light PAR and 28 % of high light R/FR ratio ( ratio of red to far red light), and simulated the canopy-like shade th at may be relevant to this species in its natural habitat. Plants grow ing under different light treatments did not show significant differen ces in total plant dry weight, total number of ramets, number of prima ry ramets, number of secondary ramets, and number of branches per clon e. L. galeobdolon plants growing under high-light conditions formed sh orter internodes, shorter petioles and smaller laminas with lower SLA, and showed higher branching intensity than those growing under low-li ght conditions. Accordingly, when growing between patches of different light conditions, the primary ramets had shorter internodes, shorter petioles and smaller laminas with lower SLA in high-light than in low- light patches. Exposing the apical region, of an otherwise shaded stol on, to high light shortened its internodes, compared with those of pla nts growing entirely under low-light conditions. Shading the apical re gion, of otherwise unshaded stolon, had no effect on the lengths of th ese internodes. In contrast, the morphology of the leaf responded to l ocal light conditions only. Elongation of stolon internodes was comple ted much faster (within 2 or 3 wk) than lamina expansion and petiole e xtension, which took at least 6 wk. These results are interpreted in t erms of the efficiency of exploitation of high-light patches within th e habitat of L. galeobdolon.