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- Author or Editor: G.W. Stutte x
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The growth of candidate crops in high CO2 environments is being investigated as part of NASA's goal of using higher plants for bioregenerative life support systems. Tomato (Lycopersicon esculentum Mill.) cvs. Red Robin and Reimann Philipp were grown in recirculating hydroponics at 400, 1200, 5000, or 10,000 μmol·mol–1 CO2 for 105 days. The plants received a 12/12 hour photo-period at 500 μmol·m–2·s–1 PPF, 26/22°C (light/dark), and 65% continuous relative humidity. Stomatal conductance increased at the highest CO2 levels, which is similar to what we have reported with Soybean, radish, and potato. Fruit number increased with increasing CO2, where Red Robin produced 663 fruit/m2 and Reimann Philipp produced 6870 fruit/m2 at 10,000 μmol·mol–1 CO2. Fruit fresh mass was greatest at 10,000 μmol·mol–1 CO2 for Red Robin (7.4 kg·m–2) and at 5000 μmol·mol–1 CO2 for Reimann Philipp (27 kg·m–2), suggesting that very high CO2 was not detrimental to yields. These findings contrast with those of wheat, soybean, and potato, which have shown slightly depressed yields at CO2 levels above 1200 μmol·mol–1.
Microcuttings of three western black cherry (Prunus serotina var. virens Ehrh.) phenotypes obtained from seedling trees with profuse or scant root systems were grown in two container sizes to examine the early effects of root constraint. Because manual methods to estimate root length and other characteristics are time consuming and subjective, an image analysis hardware and software system (image capture and analysis system) was used to classify and measure the roots. There was a significant effect of clone on fine-root surface area, coarse: fine root ratio, and root dry weight (P ≤ 0.05), but root characteristics (profuse or scant root development) of the parent material were absent in the vegetative propagules from these lines. Container size had no significant effect on coarse- or fine-root surface area but did reduce coarse: fine root ratio (P ≤ 0.05). A threshold effect of container size on root dry weight was detected (P ≤ 0.1).
Potatoes (Solanum tuberosum cv. Norland) were grown for 105 days in a large (20 m2), closed chamber to assess their potential for life support in space. Cultural conditions included a recirculating NFT culture, 12/12 photoperiod, 16°C, 1000 μmol mol-1 CO2, and approximately 900 μmol m-2 s-1 PPF from HPS lamps. The chamber was separated into two halves with one atmosphere continuously passed through charcoal filters, while the other was not filtered. Plants grown in the filtered air showed a more “induced” appearance early in growth in comparison to plants in the unfiltered air (i.e. reduced shoot growth and early tuber bulking). Ethylene levels in the atmospheres ranged from 10 to 60 ppb in the unfiltered treatment and 10 to 40 ppb in the filtered. Mass spectral analyses indicate that the filters efficiently reduced heavier organic volatiles, but were not effective for lighter volatiles (e.g. ethylene). Biogenic emissions from the plants were identified, as well as components from glues and caulking compounds. Final tuber yields were similar but shoot biomass was higher and harvest index lower in the unfiltered treatment: charcoal filtered--10.1 kg m-2 tuber FW, 1.9 kg m-2 tuber DW, 2.5 kg m-2 total plant DW, 76% harvest index; unfiltered--10.9 kg m-2 tuber FW, 1.9 kg m-2 tuber DW, 3.1 kg m-2 total plant DW, and 61% harvest index.
This experiment was performed to test the hypothesis that tuber formation in potato is inhibited by short-term increases in root-zone temperature. Micro-propagated potato cv. Norland plantlets were grown in recirculating nutrient film culture under daylight fluorescent lamps at 350 μmol·m–2·s–1 PPF with at 20/16°C thermocycle at 1200 μmol·mol–1 CO2 under inductive (12-hr light/12-hr dark) or non-inductive (12-hr light/12-hr dark with a 15-min light break 6 hr into the cycle) photoperiods for 42 days. Root-zone treatments consisted of continuous 18°C, continuous 24°C, 18°C with a 24°C cycle between 14 and 21 DAP (prior to tuber initiation), and 18°C with a 24°C cycle between 21 and 28 DAP (during the period of tuber initiation). The root-zone temperature was maintained with a recirculating, temperature-controlled, heat-exchange coil submerged in each nutrient solution. Warm root-zone temperatures did not inhibit tuber formation under an inductive photoperiod. The non-inductive photoperiod resulted in a 65% reduction in tuber biomass compared to the inductive photoperiod. Continuous 24°C and exposure to 24°C prior to tuber initiation reduced tuber formation an additional 40% under the non-inductive photoperiod. Both continuous and transient 24°C root-zone temperatures increased biomass partitioning to root/stolons compared to the 18°C treatment under both photoperiods. Total plant biomass was highest in plants exposed to continuous 24°C under both photoperiods. Results suggest that transient episodes of warm (24°C) root-zone temperature do not inhibit tuber formation in potato under inductive photoperiods. However, transient episodes of warm (24°C) root-zone temperatures did interact with stage of development under the non-inductive photoperiod.
The effects of elevated CO2 on stomatal density and index were investigated for five crop species currently being studied for NASA's Advanced Life Support program. Lettuce (cv. Waldmann's Green) and radish (cv. Giant White Globe) were grown at 400, 1000, 5000, or 10,000 μmol·mol–1 CO2, tomato (cvs. Red Robin and Reimann Philip 75/59) were grown at 400, 1200, 5000, or 10,000 μmol·mol–1 CO2, and wheat (cv. Yecora Rojo) and potato (cv. Denali) were grown at 400, 1000, or 10,000 μmol·mol–1 CO2 within controlled-environment growth chambers using nutrient film technique hydroponics. Leaf impressions were made by applying clear silicone-based RTV coating to the adaxial and abaxial leaf surfaces of three canopy leaves of each crop at each CO2 treatment. Impressions were examined using a light microscope, whereby the number of stomatal complexes and epidermal cells were counted to calculate stomatal density and stomatal index. Results indicate that stomatal density increased for lettuce and radish at 10,000 μmol·mol–1 CO2, whereas tomato density was highest at 1200 μmol·mol–1 CO2. Potato had the lowest density at 1000 μmol·mol–1 CO2, and there was no effect of CO2 on density for wheat. Stomatal index correlated with density for lettuce and tomato; however, stomatal index for radish, potato, and wheat was not influenced by CO2. This suggests that there may be a species-specific CO2 response to epidermal cell size that influences stomatal density and stomatal index.
Abstract
In observing the growth phases of a plant’s many structures, a paraphrasing of J.L. Harper (7), and later Sussman and Douthit (13), comes to mind: “Some structures are born dormant, some achieve dormancy, and some have dormancy thrust upon them”. Indeed, the dormancy phenomena can be associated with essentially all meristematic regions of the plant. Accordingly, a wealth of terminology has arisen to describe various plant dormancy phenomena. While recently discussing seasonal growth processes, our use and misuse of current and historic dormancy terms led us to conclude that a simplified, descriptive dormancy terminology would be of benefit to the plant science community. Our purpose here is to review briefly the terminology now in use, critically examine dormancy phenomena and reduce terminology to a minimal number of descriptive terms, and consequently to stimulate discussion of this terminology scheme by our peers.
The effects of planting density and short-term changes in photoperiod on the growth and photosynthesis of bean (Phaseolus vulgaris L.) was investigated. Two cultivars of bean (cv. Etna, a dry bean variety; cv. Hystyle, a snap bean variety) were grown using nutrient film technique hydroponics in a walk-in growth chamber with a 12 h/12 h (light/dark) photoperiod and a corresponding thermoperiod of 28/24 °C (light/dark) and constant 65% relative humidity. Lighting for the chamber consisted of VHO fluorescent lamps and irradiance at canopy level was 400 μmol·m-2·s-1 PPF. For each cultivar, plants were grown at densities of 16 or 32 plants/m2. Short-term photoperiod changes were imposed during vegetative growth (21-29 DAP) and pod-fill (42-57 DAP). From the base 12 h/12h (light/dark) photoperiod, lighting in the chamber was cycled to provide 18 h/06 h (light/dark) or 24 h/0 h(continuous light) for 48 h. Diurnal single leaf net photosynthetic rates (Pn) and net assimilation vs. internal CO2 (Aci) measurements were taken during the short-term photoperiod adjustments. Results showed that there was no difference between cultivars or planting density with regard to total biomass or single leaf photosynthetic rates, but cv. Etna produced 35% more edible biomass than cv. Hystyle. Additionally, there was no effect of short-term photoperiod adjustment on single leaf Pn or Aci.