Four-month-old, aseptically raised Phalaenopsis Atien Kaala `TSC 22' seedlings 1.0 cm in leaf spread were transferred (Nov. 1995) 25 per polycarbonate box to an agar medium and placed under 10, 20, 40, or 80 mol·–2·s–1 PPF from cool-white fluorescent tubes. In June 1996, plants grown under 40 or 80 mol·–2·s–1 PPF had greater mass, wider leaves, and more roots than those under the two lower PPF. Plants were then transplanted and grown in a greenhouse (GH) under 340, 170, or 85 mol·–2·s–1maximum PPF. In May 1997, plants previously produced under 40 mol·–2·s–1 PPF had longer, wider, and thicker leaves than those under 10 mol·–2·s–1 PPF when grown under the two higher GH PPF. Under the low GH PPF, however, plants were equally small, regardless of the previous flasking PPF levels. Plants under the high, medium, and low GH PPF had an average of 61, 37, and 17 g of fresh mass, respectively. By September 1997, plants had increasingly larger leaves and higher concentrations of malic acid, sugars, and starch as GH PPF increased. Each doubling in GH PPF resulted in more than a two-fold increase in plant fresh mass. Under the low GH PPF, plants previously produced under 80 mol·–2·s–1 PPF during flasking were 13% larger than those under 10 mol·–2·s–1 PPF. Plants grown under the high, medium, and low GH PPF had 100%, 79%, and 0% flowering, respectively. Those under the high GH PPF bloomed earlier and had longer inflorescences, bearing many more and larger flowers, than those under the medium GH PPF.
Greenhouse production contributes to pesticide occurrences in Swedish streams
