Growth response of skyflower (Thunbergia grandiflora Roxb.) to varying light intensities

Light is a critical factor in the growth and development of plants. This study focused on Skyflower (Thumbergia grandflora Roxb.), an invasive alien ornamental vine which is slowly invading Mount Makiling, Philippines. Skyflowers were grown in the Greenhouse and Field under three light intensities (open condition : 0% shade, partial shade: 50% shade, and complete shade: 70% shade). The following morpho-ecological characters were measured: plant height (mm) stem thickness (mm), number of leaves, number of nodes, biomass (g), chlorophyll content (SPAD value), and leaf area (cm sup 2). Based on Analysis of Variance (ANOVA) results, there was little significant difference for the data gathered between the two locations (greenhouse and field). Based on Bonferonni's method at 5% level of significance, plant height, number of leaves, number of nodes were higher in open condition and partial shade compared to those grown in complete shade. However, there was no significant difference in mean stem thickness, biomass and chlorophyll in all treatments. Leaf area was smaller in plants grown in the open condition compared to plants grown in partial and complete shade. Based on preliminary field observation on the Northeastern slopes of Mount Makiling most of the skyflowers were present at 0-100 (meter) elevation, 0-3 slopes (less steep areas), and mostly found at the North, Northeast and East directions. Results suggest that Skyflower has a strong morphological plasticity in open and partially shaded areas but can still thrive in complete shade. It is capable of smothering canopies and is continually spreading on the lower slopes of Mount Makiling. Thus, it is necessary to identify priority areas for extirpation of Skyflower to prevent further expansion inside the natural forest of Mount Makiling Forest Reserve, Luzon, Philippines.