The effects of in vitro and greenhouse irradiance, fertility, and media on the growth of a hybrid Phalaenopsis orchid

Abstract

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 [ molem-2*s-1 PPF] from cool-white fluorescent tubes. In June 1996, plants grown under 40 or 80 [ molom-2*s-I 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 12%, 5.4% or 2.6% of full sunlight. In May 1997, plants previously produced under 40 [limolom-2os-1] PPF had longer, wider, and thicker leaves than those under 10 [2*s-I PPF] when grown under the two higher GH PPF. 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 [molem-2*s-l] PPF during flasking were 13% larger than those under 10 [ umol2*s-l PPF]. In a separate experiment, one of five fertilizers, [1 ON-1 3. 1-P-I 6.6K@ 2ON-2.2-P15.SK, 2ON-8.6-P-16.6K], DynaGro, and Wilder's, was applied to Phalaenopsis Atien Kaala 'TSC 22' plants grown in either fir bark alone or 70% fir bark and 3 0% Canadian sphagnum peat (bark/peat). Plants grown in the fir bark medium with 2ON-2.2P-I 5.8K fertilizer had more leaf production, greater leaf fresh mass, greater total leaf area and greater root fresh mass than with any other fertilizers. In the bark/peat medium, the [2ON2.2P-I 5.8K and 2ON-8.6P-I 6.6K] fertilizers resulted in similar leaf production, greater fresh mass, greater area, and greater root fresh mass than the other fertilizers. The bark medium, regardless of fertilizer, had higher pH and lower EC then the bark/peat medium. The bark/peat medium had higher concentrations of NH4+, N03-, Ca, Fe, Na, Cl, B and Al in the leachate. Media and fertilizers had little effect on the mineral composition of the leaves.