Utilization of potatoes for life support systems in space. I. Cultivar-photoperiod interactions

The productive potential of potatoes (Solanum tuberosum L. cvs. Norland, Superior, Norchip, and Kennebec) was assessed for life support systems being proposed for space stations and/or lunar colonies. Plants were grown in walk-in-growth rooms for 15 weeks at 20 C under 12-, 16- and 20-h photoperiods of 400 micromoles m-2 s-1 photosynthetic photon flux (PPF). Norland yielded the greatest tuber fresh weight, producing 2.3, 2.4, and 2.9 kg/plant under 12-, 16-, and 20-h photoperiods, respectively. The respective yields for the other cultivars under 12-, 16-, and 20-h were: Superior, 1.9, 1.5, and 1.8 kg/plant; Norchip, 1.8, 1.4, and 2.0 kg/plant; and Kennebec, 2.3, 0.2, 0.8 kg/plant. Shoot and total plant biomass increased with lengthening photoperiods except for Kennebec, which showed increased shoot growth but no change in total growth with the longer photoperiods. Kennebec shoot growth under the 20-h photoperiod, and to some extent under 16-h, was noticeably stunted with shortened internodes. In addition, leaves of these plants showed mild chlorosis with rusty "flecking" of the surfaces. The harvest index (ratio of tuber yield/total biomass) was highest for all cultivars under the 12-h photoperiod, with a maximum of 0.69 for Norland. Similarly, the tuber yield per input of irradiant energy also was highest under 12-h for all cultivars. The tuber yield expressed on an area basis for the highest yielding treatment (Norland under 20-h) equaled 2.2 kg dry matter m-2. Over 15 week this equates to a productivity of 20.7 g tuber dry matter m-2 day-1. Assuming 3.73 kcal per g tuber dry matter and a daily human dietary requirement of 2800 kcal, then 36 m2 of potatoes could supply the daily energy requirement for one human. Potential for increasing productivity is discussed.