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  • Author or Editor: K. A. Corey x
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Yields and quality of witloof chicory are often low when roots are forced following several months storage or when forced at high temperatures. A technique was developed to improve the yield and quality of the chicons forced hydroponically and a method developed to determine the rates of respiration and ethylene production during the application of the technique. The technique involves the use of a resilient material (polyurethane) combined with the application of pressure to the developing chicons. Marketable yields and density of `Faro' and `Bea' chicons increased with increasing pressure applied. Increasing pressure also resulted in a significant decrease in the length to diameter ratio of chicons, an indicator of improved quality. Mechanical pressure resulted in a 3 to 4 fold greater increase in ethylene production than the control. Respiration rate increased to about twice that of the control after 10 days forcing and thereafter declined slightly. The technique provides a tool for improving economic yields of hydroponically forced witloof chicory. A possible physiological explanation for the technique is provided.

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Authors: and

Abstract

Storage losses of apparently sound roots from flooded plots with vines mowed or completely removed were greater than intact vines for ‘Jewel’ but not ‘Centennial’ sweet potato [Ipomoea batatas (L.) Lam.]. Vine removal accentuated the detrimental effects of flooding, possibly by elimination of a possible route for ethanol removal from the roots. Ethanol concentration at harvest from flooded plots was greater in roots with vines removed than from roots with intact vines. Vine removal lowered yield of ‘Jewel’ and lowered percent dry matter of both ‘Jewel’ and ‘Centennial’.

Open Access

Abstract

Tomato (Lycopersicon esculentum Mill. cv. Heinz 1350) plants grown in soil with N supplied from (NH4)2SO4 solutions showed a morphological disorder characterized by leaf epinasty. The development of this disorder was accompanied by an increase in the rate of ethylene evolution from whole plants. Ethylene evolution from plants supplied with 0.04 m NH4-N increased to a peak of 112 nl·g−1·hr−1 at ≈2 weeks following the start of fertilization compared to 11 nl·g−1·hr−1 from plants supplied with 0.04 m NO3-N. Fertilization with KC1 in molar equivalency to the supply of NH4-N prevented epinasty and the burst in ethylene evolution. Ethylene evolution from plants of the yellow-green-5 and neglecta-1 mutants did not increase in response to NH4-N fertilization. Potassium concentrations in shoots of ‘Heinz 1350% yellow-green- 5, and neglecta-1 were 2.10, 2.53, and 3.22% (dry weight), respectively, if plants were supplied with NH4-N and no additional K, suggesting that tolerance to NH4 toxicity may be explained in part by differences in K accumulation.

Open Access

Abstract

The effect of 24, 48, and 72 hours of soil saturation on the ethanol concentration of roots at harvest and on postharvest storage loss was investigated for sweet potato [Ipomoea batatas (L.) Lam. cvs. Jewel and Centennial]. Ethanol accumulated rapidly with increasing time of soil saturation for both cultivars. Ethanol concentration was greater in roots taken from soil with slow drainage rates following saturation than from roots grown in soil with a fast drainage rate. The ethanol concentration in ‘Centennial’ roots did not increase beyond 48 hour saturation in soil with good drainage following saturation, while ethanol accumulated in ‘Jewel’ roots up to 72 hours. Weight loss in storage due to shrinkage and rotting was greatest for Jewel when subjected to 72 hours of continuous saturation followed by poor drainage, but as little as 24 hours of soil saturation followed by poor drainage caused significant storage losses.

Open Access

Abstract

A method was developed for determining internal gas pressure changes of pickling cucumbers (Cucumis sativus L.) during brine storage. Internal pressure decreased by 55 mm Hg during the first hour after the control fruit had been submerged in brine and then gradually increased over the next 2 hours to about the level of atmospheric pressure that had existed immediately after brining. With cucumbers that were gas-exchanged before brining, the pressure decreased by a maximum of 145 mm Hg when O2 was the exchange gas, and increased slightly when N2 was the exchange gas. Pressure changes in O2-exchanged cucumbers corresponded with changes in the level of brine that surrounded the fruit, suggesting that liquid entered the fruit as a consequence of the partial vacuum. O2-exchanged, brined cucumbers acquired a translucent, cured appearance, due apparently to filling of the intercellular gas spaces with liquid. Mechanically induced vacuum failed to induce the cured appearance. Respiratory conversion of O2 to CO2 in control and in O2-exchanged fruit, with greater dissolution of the CO2 than the O2 which it replaced, is thought to account for the partial vacuum that develops in brined cucumbers.

Open Access

Soybean plants [Glycine max (L.) Merr. cv. McCall] were grown from seed to harvest (90 days) in NASA's Biomass Production Chamber. The chamber provides approximately 20 m2 of growing area with an atmospheric volume of 113 m3. Photosynthesis and respiration rates of the stand were tracked by monitoring CO2 increase during the 12-h dark period and the subsequent drawdown to controlled set point (1000 ppm) when the lamps were turned on each day. Stand photosynthesis [under 875 μmol m-2 s-1 photosynthetic photon flux (PPF)] peaked at 35 μmol m-2 s-1 at 30 to 35 days after planting (DAP) and averaged 22 μmol m-2 s-1 throughout the life cycle. Dark period respiration peaked near 8 μmol m-2 s-1 at 30 to 35 DAP and averaged nearly 5 μmol m-2 s-1 throughout the life cycle. Prior to full canopy closure near 30 DAP, the light compensation point (LCP) for stand photosynthesis was lass than 100 μmol m-2 s-1 PPF; by 54 DAP the LCP had increasad to 175 μmol m-2 s-1. Stand transpiration rates peaked at 8.2 L m-2 day-1 at 40 to 45 DAP and averaged 4.3 L m-2 day-1 throughout growth.

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A wheat (Triticum aestivum cv. Yecora Rojo) stand was grown using nutrient film culture in the closed conditions of NASA's Biomass Production Chamber. Rates of photosynthesis and respiration of the entire stand (about 20 m2) were determined daily using a regime of 20 hr light/4 hr dark, 20 C light/16 C dark an average PPF of 600 μmol/m2/s from HPS lamps, and a CO2 cone of 1000 ppm. Fractional interception of PPF by the stand reached a maximum of 0.96 at 24 days from planting. Rates of photosynthesis were constant throughout the photoperiod as determined by short term drawdowns of CO2 throughout the photoperiod. Drawdown rates of CO2 were correlated with rates determined by logging of mass flow of CO2 injected during chamber closure. Photosynthetic drawdowns of CO2 indicated that photosynthesis was not saturated at 1000 ppm CO2 and that the CO2 compensation point was about 50 ppm. Whole stand light compensation points were 200 to 250 μmol/m2/s between days 13 and 70 and then increased rapidly during senescence.

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Ethylene concentrations were monitored using gas chromatography (GC/PID) throughout growth and development of wheat, soybean, and lettuce stands grown hydroponically inside a large, closed growth chamber (20 m2 area, 113 m3 vol.). For wheat (cv. Yecora Rojo), ethylene concentration increased from < 10 ppb to about 120 ppb at about 28 days after planting (pre-anthesis) and then declined sharply over the next 4 weeks to a plateau of about 10 ppb during canopy maturation and senescence. A similar pattern of evolution was measured for soybean stands (cv. McCall), with peak concentrations of 40 to 70 ppb occurring near 50 days after planting. Unlike wheat, a slight increase in ethylene was noted in the latter stages of soybean stand senescence. For lettuce stands (cv. Waldmann's Green), ethylene increased slowly to 10 to 15 ppb by 24 days after planting, and then rose sharply to 40 ppb by 28 days, when plants were harvested. Data will be used to define ranges for phytotoxicity studies and to project atmospheric contaminant control needs for tightly closed plant growth systems.

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