|MadSci Network: Botany|
I encourage you NOT to make the assumption that English bluebell (Hyacinthoides non-scriptus) [formerly Scilla non-scripta, Endymion non-scripta] prefers shaded areas without scientific evidence. Spring bulbs start growing before the trees leaf out so are exposed to high light early in the season. There is also typically a strong interaction between light intensity and soil moisture in shade tolerant plants. Many species that are said to "prefer" shade will actually grow much better in full sun, than in shade, if there is adequate soil moisture. Examples are caladium and impatiens. Other species are obligate shade plants, such as African violet, and their leaves are damaged in full sun. Another thing to consider is if competing species in higher light areas outcompete bluebell making competition and not light the key factor in distribution. This appears to be the case with bluebell and bracken fern. In higher light, the taller bracken fern is more vigorous, grows taller sooner, and shades out the bluebell. In shady areas, the bracken fern grows more slowly, which allows the bluebell to receive adequate light before its leaves die back in the summer. It is often difficult to collect good experimental data under natural conditions because the environment is so variable. Experimentally, it would be desirable to grow bluebells in containers to standardize soil conditions (optimal water, fertilizer, soil aeration, soil pH, lack of soil borne diseases). This would allow a fair comparison of growth under different light intensities, by using shade cloth or growth chambers. It would be best to exactly quantify light level with a quantum sensor (see LI-COR) measuring PAR (Photosynthetically Active Radiation). With natural light, it is best to measure the daily total of PAR in moles per square meter because instantaneous readings vary widely throughout the day, particularly in dappled shade. PAR is the best way to quantify light for photosynthesis. To do a long term growth study, you would need to measure weight gain, perhaps measuring just the bulb weight would be easiest as it could be done at the start and at the end of the experiment. Otherwise, you could measure total weight of leaves and flowers. Shorter term photosynthesis experiments would require an expensive lab system to measure photosynthesis of a single leaf or single plant under various PAR levels (see LI-COR). References Bluebell Info Summary LI-COR Photosynthesis and photoprotection in Quercus ilex resprouts after fire Solar Radiation and Photosynthesis
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