Growth Under Metal Hailide and Microwave Powered Sulphur Lamps

Appearance of 'Poinsett' cucumber plants grown for 14 days in a growth chamber under six 400 W metal halide (MH) lamps and under a single 1000 W microwave powered sulphur plasma lamp (MPS).

Note space between MH grown plants and the absence of space between MPS grown plants and the fact that pot labels are still visible among the MH grown plants but not the MPS grown plants.

BIOTRONICS 27. 81-92, 1998

UNIFORMITY OF PHOTOSYNTHETIC PHOTON FLUX AND GROWTH OF 'POINSETT' CUCUMBER PLANTS UNDER METAL HALIDE AND MICROWAVE-POWERED SULFUR LAMPS

D. T. KRIZEKR~., M . MIRECKaI nd W. A. BAILEY

Climate Stress Laboratory, Natural Resources Institute, Agricultural Research Service,
U.S. Department of Agriculture, Beltsville, MD 20705-2350, USA

(Received September 11, 1998; Accepted October 1, 1998)

KRIZEKD, . T.. MIRECKIR. . M. and BAILEYW, . A. Uniformity of photosynthetic photon flux and growth of 'Poinsett' cucumber plants under metal halide and microwavepowered sulfur lamps. BIOTRONICS 27, 81-92. The uniformity of photosynthetic photon flux (PPF) and vegetative growth of Cucumis sativus L. ('Poinsett' cucumber) were examined using growth chambers equipped with either six 400 W metal halide (MH) lamps or with a single 1000 W microwave -powered sulfur (MPS) (LIGHTDRIVETM 1000) lamp mounted on a polished stainless steel reflector with secondary screening for microwave protection.

PPF levels in each growth chamber were set initially at 500pmol m-2 s-I. Pots were placed at equal distance from one another in ten columns of six rows each (n=60). Growth measurements were only taken on the center six columns of plants (n=36). The uniformity of PPF was greater in the MPS than in the MH chamber for both the 36 and the 60 pot arrangement. However, growth measurements showed similar variance in the MH as in the MPS chamber. Plants grown for 14 days under MPS lamps had significantly greater growth than those under MH lamps. Petiole length, total stem length, and leaf enlargement were 90%, 44%. and 34% greater, respectively. in plants grown under MPS lamps than under MH lamps. Similar differences were obtained in biomass; dry weights of tops and roots of MPS grown plants were 28% and 36%, greater, respectively, than those of MH grown plants. These findings demonstrate the potential of using sulfur lamps for accelerating seedling production under controlled environments and validate the concept that sulfur lamps have a better spectral quality for plant growth than metal halide lamps. These results should be of interest to growers and researchers involved in protected cultivation. The LIGHTDRIVETM 1000 sulfur lamp should also provide a useful tool for studying the photocontrol of shoot development....