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This article in AJ

  1. Vol. 83 No. 5, p. 903-906
     
    Received: Nov 26, 1990
    Published: Sept, 1991


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doi:10.2134/agronj1991.00021962008300050024x

Soybean Stem Growth under High-Pressure Sodium with Supplemental Blue Lighting

  1. R. M. Wheeler ,
  2. C. L. Mackowiak and
  3. J. C. Sager
  1. N ASA Biomedical Operations and Research Office
    T he Bionetics Corp., Kennedy Space Center, FL 32899

Abstract

Abstract

High-pressure sodium (HPS) lamps are popular for plant lighting because of their high energy conversion efficiencies. Yet their spectrum has very little blue light (BL), which may cause undesirable morphological responses. To study this, ‘McCall’ soybean [Glycine max (L.) Merr.] plants were grown for 28 d in growth chambers using HPS lamps, with or without supplemental light from blue phosphor fluorescent lamps. Total photosynthetic photon flux (PPF) levels (including blue fluorescent) were kept near 300 or 500 µmol m−2 s−1. Blue fluorescent levels ranged from 7 to 20 µmol m−2 s−1, providing from 6 to 18 µmol m−2 s−1 of supplemental BL (400-500 nm). Stem and internode lengths were longest under 300 µmol m−2 s−1 HPS lighting and became progressively shorter with increasing supplemental BL until a total of approximately 30 µmol m−2 s−1 of BL (from HPS and BL supplement) was present in the spectrum. Beyond this, extra BL had no effect. Two other lamps rich in BL, metal halide (Optimarc) and fluorescent (Vita-Lite), also produced plants with short stems, as did HPS lighting maintained at 500 µmol m−2 s−1. Results suggest that use of high-pressure sodium or other blue-deficient sources for lighting at low to moderate photosynthetic photon flux levels may cause abnormal stem elongation, but this can be prevented by adding a small amount of supplemental blue light.

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