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Abstract
Sixty-nine species of ornamental plants were screened for A1 tolerance in greenhouse pots of acid Tatum subsoil adjusted to different pH levels by liming. Species differed widely in tolerance to the unlimed soil at pH 4.1-4.4. For example, in one experiment the relative top yield on unlimed vs. limed soil (pH 4.3/pH 5.2) was 71% for Dolichos lablab L. (hyacinth bean); 63% for Tropaeolum majus L. (nasturtium); 62% for Cleome spinosa Jacq. (cleome); 59% for Calonyction aculeatum L. (moonflower); 18% for Tagetes erecta L. (marigold); 11% for Cosmos sulphureous Cav. (cosmos); 4% for Calendula officinalis L. (calendula); and 0.8% for Chrysanthemum coronarium L. (garland chrysanthemum). With the exception of cleome, the acid-soil-tolerant species were larger seeded than the sensitive species. Ornamental species also differed in tolerances to neutral-alkaline Tatum soil (pH 7.0-7.2). For example, relative top yields on high lime vs. low lime soil (pH 7.1/5.1) were 89% for marigold, 87% for cleome, 79% for calendula, 78% for hyacinth bean, 54% for nasturtium and 11% for garland chrysanthemum. Ornamental plants were classified according to suitability for strongly acid (pH 4.1-4.4), moderately acid (pH 5.1-5.4) or neutral to alkaline (pH 7.0-7.2) Tatum subsoil.
Growth measurements of potato (Solanum tuberosum L.) cvs. Norland (NL), Denali (DN), and Kennebec (KN) were taken from 21-day-old plantlets grown in vitro. Studies were conducted in a growth chamber, with nodal explants grown in culture tubes with loose-fitted Magenta 2-way caps containing Murashige and Skoog salts with either 0, 1, 2 or 3% sucrose. The cultures received either 100 or 300 μmol m-2 s-1 photosynthetic photon flux (PPF), and the growth chamber was maintained at either 400 or 4000 μmol mol-1 CO2. All cvs. showed significant increases in growth on 0% sucrose media at 4000 μmol mol-1 CO2, indicating an autotrophic response. At 400 μmol mol-1 CO2, all cvs. showed an increase in total plantlet dry weight (DW) with increasing sucrose under both PPF levels. Within any sucrose treatment, the highest total DW for all cvs. resulted from 300 μmol m-2 s-1 PPF and 4000 μmol mol-1 CO2. At 4000 μmol mol-1 CO2, shoot DW declined with sucrose above 2% for DN and sucrose above 1% for NL at both PPF levels, suggesting that high sucrose levels may hinder growth when CO2 enrichment is used.
Leaf stomatal conductance was monitored with a steady-state porometer throughout growth and development of soybean and potato plants grown at 500, 1000, 5000, and 10,000 (potato only) μmol mol-1 carbon dioxide (CO2). All plants were grown hydroponically with a 12-hr photoperiod and 300 μmol m-2 s-1 PPF. As expected, conductance at 1000 was < 500 μmol mol-1 for both species, but conductance at 5000 and 10,000 μmol mol-1 was ≥ that at 500 μmol mol-1. Subsequent short-term (24-hr) tests with potato and wheat plants grown at 1000 μmol mol-1 showed that raising CO2 to approx. 10,000 μmol mol-1 or lowering CO2 to 400 μmol mol-1 increased conductance compared to 1000 μmol mol-1 for potato, while only lowering CO2 to 400 μmol mol-1 increased conductance for wheat. Furthermore, raising the CO2 to 10,000 μmol mol-1 increased dark-period conductance in comparison to 1000 μmol mol-1 for potato, while dark-period conductance for wheat leaves was low regardless of the CO2 concentration. Results suggest that very high CO2 levels (e.g. 5000 to 10,000 μmol mol-1) may substantially increase water use of certain crops.
Lettuce (cv. Waldmann's Green) and radish (cv. Giant White Globe) plants were grown hydroponically with a 18-hr photoperiod and 300 μmol m-2 s-1 PPF. Treatments consisted of 400, 1000, 5000 and 10000 μmol mol carbon dioxide (CO2). Leaf stomatal conductance was monitored with a steady-state porometer across one diurnal period at 21 days and all plants were harvested at 25 days. Conductance at 400 and 10000 was > 1000 μmol mol-1 for lettuce and conductance at 5000 and 10000 was > 1000 and 400 μmol mol-1 CO2 for radish. Carbondioxide treatments having the lowest leaf conductances also resulted in the highest yields, viz. 1,000 μmol mol-1 CO2 for radish and 5000 μmol mol-1 CO2, for lettuce. Dark-period conductance was higher at 5000 and 10000 μmol mol-1 CO2 compared to 400 and 1000 μmol mol-1 CO2. The higher dark-period conductances were 70% of the light-period rates for lettuce and 30% for radish. Water use efficiency (WUE) (g biomass kg water-1) was lowest at 400 μmol mol-1 CO2 for both lettuce and radish and was highest at 1000 μmol mol-1 CO2 for lettuce and 5000 μmol mol-1 CO2 for radish. The results suggest that WUE was improved with moderate CO2 enrichment but declined at very high concentrations, i.e. 10000 μmol mol-1 for lettuce and radish.
Photoperiod treatments were imposed on potato (Solanum tuberosum L. cv. Norland) grown in the Biomass Production Chamber (BPC) at Kennedy Space Center under HPS lamps (670 μmol m-2s-1 PPF) at 1200 μmol mol-1 CO2. Stand A decreased with dark cycle length, which correlated with the change in leaf starch concentration during the dark cycle, but not absolute starch concentration. A series of growth chamber experiments were performed to characterize the effect of photoperiod and PPF on CO2 assimilation and starch mobilization in single leaves. Plants grown on a 12/12 photoperiod at either low (300 μmol m-2s-1) or high (600 μmol m-2s-1) PPF were subjected to short-term photoperiod treatments of 8/16, 16/8, and 24/0 and diurnal CO2 assimilation rates, CO2 response curves, and leaf starch content were determined. CO2 compensation point was not affected by either photoperiod or PPF. However, Amax (when normalized for PPF) decreased with increasing photoperiod. Anet correlated with the changes in specific leaf weight and starch content during the dark cycle.
Potato (Solanum tuberosum L. cvs. Norland and Denali) plants were grown under high-pressure sodium (HPS), metal halide (MH), and blue-light-enhanced SON-Agro high-pressure sodium (HPS-S) lamps to study the effects of lamp spectral quality on vegetative growth. All plants were initiated from in vitro nodal cultures and grown hydroponically for 35 days at 300 μmol·m–2·s–1 photosynthetic photon flux (PPF) with a 12-hour light/12-hour dark photoperiod and matching 20C/16C thermoperiod. `Denali' main stems and internodes were significantly longer under HPS compared to MH, while under HPS-S, lengths were intermediate relative to those under other lamp types, but not significantly different. `Norland' plants showed no significant differences in stem and internode length among lamp types. Total dry weight of `Denali' plants was unaffected by lamp type, but `Norland' plants grown with HPS had significantly higher dry weight than those under either HPS-S or MH. Spectroradiometer measurements from the various lamps verified the manufacturer's claims of a 30% increase in ultraviolet-blue (350 to 450 nm) output from the HPS-S relative to standard HPS lamps. However, the data from `Denali' suggest that at 300 μmol·m–2·s–1 total PPF, the increased blue from HPS-S lamps is still insufficient to consistently maintain short stem growth typical of blue-rich irradiance environments.
The vegetative growth of potato (Solanum tuberosum L.) cvs. Norland (NL) and Denali (DN) was investigated comparing SONAGRO high-pressure sodium (HPS-S), standard high-pressure sodium (HPS), and metal halide (MH) lamps. Plants were initiated from nodal culture and grown hydroponically in a reach-in growth chamber for 35 d with a 12-hr light/12-hr dark photoperiod and corresponding thermoperiod of 20/16 C. PPF for each treatment was maintained at 300 μmol m-2 s-1 and CO2 levels maintained at l000 μmol mol-1 to promote growth. Results showed that main stem length (SL) and number of internodes (INT) for DN were significantly higher under HPS compared to MH, while HPS-S was not significantly different from the other lamp types. Total dry weight (TDW) of NL plants was significantly higher for HPS than for either HPS-S and MH, however there was no significant difference in SL and INT among lamp types. The data suggest that the 12.6% increase in blue light (400-500 nm) with HPS-S in comparison to conventional HPS lamps may not be sufficient to consistently decrease the stem elongation effects commonly seen with plants grown under HPS.
Radish (Raphanus sativus cv. Giant White Globe) and lettuce (Lactuca sativa cv. Waldmann's Green) plants were grown for 25 days in growth chambers at 23 °C, ≈300 μmol·m-2·s-1 PPF, and 18/6 photoperiod, and four CO2 concentrations: 400, 1000, 5000, and 10,000 μmol·mol-1. Average total dry mass (g/plant) at the 400, 1000, 5000 and 10,000 μmol·mol-1 treatments were 6.4, 7.2, 5.9, and 5.0 for radish and 4.2, 6.2, 6.6, and 4.0 for lettuce. Each species showed an expected increase in yield as CO2 was elevated from 400 to 1000 μmol·mol-1, but super-elevating the CO2 to 10,000 μmol·mol-1 resulted in suboptimal growth. In addition, many radish leaves showed necrotic lesions at 10,000 μmol·mol-1 by 17 days and at 5000 μmol·mol-1 by 20 days. These results are consistent with preliminary tests in which radish cvs. Cherry Belle, Giant White Globe, and Early Scarlet Globe were grown for 16 days at 400, 1000, 5000, and 10,000 μmol·mol-1. In that study, `Giant White Globe' produced the greatest total dry mass at 1000 (3.0 g/plant) and 5000 μmol·mol-1 (3.0 g/plant), and the least at 10,000 μmol·mol-1 (2.2 g/plant). `Early Scarlet Globe' followed a similar trend, but `Cherry Belle' showed little difference among CO2 treatments. Results suggest that super-elevated CO2 can depress growth of some species, and that sensitivities can vary among genotypes.
Peanut (Arachis hypogaea L.) plants were grown hydroponically, using continuously recirculating nutrient solution. Two culture tray designs were tested; one tray design used only nutrient solution, while the other used a sphagnum-filled pod development compartment just beneath the cover and above the nutrient solution. Both trays were fitted with slotted covers to allow developing gynophores to reach the root zone. Peanut seed yields averaged 350 g·m-2 dry mass, regardless of tray design, suggesting that substrate is not required for hydroponic peanut production.
As part of NASA's effort with bioregenerative life support systems, the growth of candidate crops is being investigated in controlled environments. Peanut (Arachis hypogaea L.) was selected for the high oil and protein content of its seed. Peanut cvs. Pronto and Early Bunch were grown from seed, using recirculating nutrient film technique (NFT) in 6-cm-deep, trapazoidal culture trays. The trays were fitted with slotted covers, which allowed developing pegs to reach the root zone. Use of a separate moss-filled pegging compartment above the root zone (tray within a tray) had little effect on seed yield, but resulted in a 60% increase in the nitric acid requirements for pH control. Yields from both cultivars were equivalent to field values on an area basis; however, harvest indices were lower than field values due to the luxuriant canopy growth under controlled environment conditions. Proximate analysis of seeds was similar to field values, with the exception of fat, which was ≈15% lower, and ash, which was ≈30% greater under controlled environment conditions, regardless of cultivar.