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Continuous Daily Light Period and Temperature Influence Peanut Yield in Nutrient Film Technique

7808 S. Placita Senora Maria, Tucson, AZ 85707

D. G. Mortley^*, P. A. Loretan, C. K. Bonsi and W. A. Hill

Center for Food and Environmental Systems for Human Exploration of Space, College of Agriculture and Environmental Sciences, Tuskegee Univ., Tuskegee, AL 36088.

^* Corresponding author (mortley{at}acd.tusk.edu).

The peanut (Arachis hypogaea L.) is under investigation for use in the National Aeronautics and Space Administration's Advanced Life Support (ALS) program as a food source for extended space missions. The objective of this study was an evaluation of the effect of a continuous light period combined with constant or diurnally cyded temperatures on pod and seed yield, plant biomass, harvest index, and gas exchange in ‘Georgia Red’ peanut grown hydroponically under the nutrient film technique. Experiments were conducted in controlled-environment growth chambers. Treatments were light/ dark periods of 12/12 h or 24/0 h in combination with a constant 28 or 28/22°C. Relative humidity was 70 ± 5% and a photosynthetic photon flux (PPF) at canopy level of 250 or 500 µmol m^–2 s^–1 for 2410 h and 12/12-h light periods, respectively. Plants exposed to 24/0 h light produced more foliage biomass, lower pod and mature seed yields, and lower harvest indices. Temperature had no significant effect on foliage biomass yield. However, plants exposed to diurnal 28/22°C produced higher pod and immature seed yield and a higher harvest index. The mean number of flowers reaching anthesis was higher among plants grown at a 12/12-h light period, regardless of temperature. Leaf net photosynthetic rates and stomatal conductance were higher among plants grown at 12/12-h light period, regardless of temperature. The results suggest that, while light period influenced, foliage, pod, and seed yield, temperature influenced foliage dry mass, immature seed yield, and harvest index.

Received for publication August 11, 1998.