Guaco (Mikania glomerata Sprengel) is a medicinal species known because of its bronchi-dilating activity. Many studies have indicated changes in anatomical and physiological characteristics of medicinal plants when submitted to different conditions of light. The effect of photoperiods (8; 12; 16 and 20 h) on leaf anatomy, content of chlorophyll and stomatal conductance in distinct regions of guaco plants were analyzed. Adult plants of different sizes influenced by distinct photoperiods were submitted to anatomical and physiological analyses. 90 days after starting photoperiod treatments the chlorophyll content was higher in plants submitted to photoperiods of 8 and 12 hours in the superior and intermediary regions of plant, decreasing at 8 h of photoperiod treatment in the basal region of the plants. The conductance and stomatal density presented inverse relation to increase of photoperiod, decreasing from apical to basal regions of the plants. The thickness of the superior epidermis increased in the intermediary and basal regions of the plants submitted to a photoperiod up to 16 h. These regions presented a progressive increase of the lacunose parenchyma thickness under a photoperiod up to 20 h. The size and organization of the vascular bundles were influenced by the photoperiods.
Mikania glomerata Sprengel light; chlorophyll; stomatal conductance; leaf anatomy
