A porous stainless steel membrane system for extraterrestrial crop production.

A system was developed in which nutrient flow to plant roots is controlled by a thin (0.98 or 1.18 mm) porous (0.2 or 0.5 microns) stainless steel sheet membrane. The flow of nutrient solution through the membrane is controlled by adjusting the relative negative pressure on the nutrient solution side of the membrane. Thus, the nutrient solution is contained by the membrane and cannot escape from the compartment even under microgravity conditions if the appropriate pressure gradient across the membrane is maintained. Plant roots grow directly on the top surface of the membrane and pull the nutrient solution through this membrane interface. The volume of nutrient solution required by this system for plant growth is relatively small, since the plenum, which contains the nutrient solution in contact with the membrane, needs only to be of sufficient size to provide for uniform flow to all parts of the membrane. Solution not passing through the membrane to the root zone is recirculated through a reservoir where pH and nutrient levels are controlled. The size of the solution reservoir depends on the sophistication of the replenishment system. The roots on the surface of the membrane are covered with a polyethylene film (white on top, black on bottom) to maintain a high relative humidity and also limit light to prevent algal growth. Seeds are sown directly on the stainless steel membrane under the holes in the polyethylene film that allow a pathway for the shoots.

Comparison of fluorescent and high-pressure sodium lamps on growth of leaf lettuce.

Radiation from high-pressure sodium (HPS) lamps provided more than a 50% increased yield (fresh and dry weight of tops) of loose-leaf lettuce cultivars Grand Rapids Forcing and RubyConn, compared to that obtained by radiation from cool-white fluorescent (CWF) lamps at equal photosynthetic photon flux; yet, input wattage was approximately 36% less. It was postulated that the considerable output of 700 to 850 nm radiation from the HPS lamp was a significant factor of the increased yield. Under HPS lamps, the leaves of both cultivars were slightly less green with very little red pigmentation ('RubyConn') and slightly elongated, compared to CWF, but plant productivity per unit electrical energy input was vastly superior with HPS.

Effect of 16 and 24 hours daily radiation (light) on lettuce growth.

A 50% increase in total radiation by extending the photoperiod from 16 to 24 hr doubled the weight of all cultivars of loose-leaf lettuce (Lactuca sativa L.) 'Grand Rapids Forcing', 'Waldmanns Green', 'Salad Bowl', and 'RubyConn', but not a Butterhead cultivar, 'Salina'. When total daily radiation (moles of photons) was the same, plants under continuous radiation weighed 30% to 50% more than plants under a 16 hr photoperiod. By using continuous radiation on loose-leaf lettuce, fewer lamp fixtures were required and yield was increased.

Silver uptake, distribution, and effect on calcium, phosphorus, and sulfur uptake.

Bean, corn, and tomato plants were grown in a nutrient solution labeled with (32)P, (45)Ca, or (35)S and varying concentrations of AgNO(3). Following a 6-hour treatment period, plants were harvested and analyzed. A low Ag(+) concentration (50 nanomolar) inhibited the shoot uptake of the ions investigated. In the roots, Ca uptake increased whereas P and S uptake decreased.Autoradiograms of bean and corn plants, using (110m)Ag, showed that Ag(+) was uniformly deposited in the bean shoot, but corn shoots had regions of high activity along the leaf margins and at the tips where guttation had occurred. Roots were heavily labeled and shoots (especially the new growth) continued to accumulate Ag(+) even after the intact plant was returned to Ag-free solution. Silver was believed to be phloem-mobile since it was exported from a treated leaf. Bean plants removed one-half the Ag(+) from 4 liters of nutrient solution containing 50 nanomolar AgNO(3) within 1.5 hours, but took 16 hours for 20 liters of solution.

Phloem mobility of magnesium.

Magnesium-28 was applied to specific leaves of bean (Phaseolus vulgaris) and barley (Hordeum vulgare) plants. After 24 hours, as much as 7% of the absorbed Mg was exported from the treated bean leaves and 11% was transported basipetally from the treated zone of the barley leaves. Transport of Mg did not occur past a heat-killed section of the treated leaf, thereby indicating that translocation took place via the phloem. Mg movement in the phloem was also evident in autoradiograms of bean stem segments in which the xylem was separated from the phloem by a thin sheet of plastic.

Distribution of calcium absorbed by all or part of the root system of beans.

When either the whole root system or a single root of the bean plant (Phaseolus vulgaris L.), at different stages of maturity, was fed (45)Ca for a period of 6 hr, the leaves exhibited a definite pattern of (45)Ca acquisition with maximum acquisition for the primary, first, second, and third trifoliolate leaves at 12, 16, 18, and 22 days of growth, respectively. This maximum acquisition occurred when a leaf approached full expansion. A liquid scintillation spectrometer was employed for (45)Ca analysis.Autoradiograms indicated that when (45)Ca was applied to the terminal 5 cm portion of specific lateral roots for a period of 6 hr, specific areas of the shoot were preferentially supplied with (45)Ca. The amount of (45)Ca transported upward, when the terminal 5 cm portion of a single lateral root was treated, greatly decreased in plants older than 20 days, and the growth rate of these roots was also reduced at about the same time. When the whole lateral root was involved in (45)Ca uptake, the amount of (45)Ca transported to the shoot increased with increasing plant age until after day 22. A continuous increase in (45)Ca transport to the shoot occurred when the whole root system was subjected to (45)Ca treatment. One factor involved in the decreased movement of (45)Ca into a particular leaf may be a decreased absorptive capacity of that part of the root which preferentially supplies Ca to this leaf. Other possible factors are discussed.

Transport of rubidium absorbed by the apex of the bean root.

Rubidium-86 was applied to the terminal 5.0 mm region of intact roots for a 6 hour period. The plants were then harvested after 0, 18, 24, 48, 72, or 96 hours additional growth in a rubidium-free continuously renewed nutrient solution. A substantial portion of the rubidium absorbed in a region of the root devoid of functional xylem tissue was ultimately transported to more basipetal regions.