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G.W. Stutte

Interactive Image Capture and Analysis System (ICAS) provides for real-time capture of video images using an imaging board and software in a personal computer. Through the use of selective filters on the video input source, images of specific reflective wavelengths are obtained and then analyzed for intensity distribution using interactive software designed for scientific agriculture. Conversion of video cameras into two-dimensional near real-time visual and near infrared (NIR) spectral sensors through the use of filters provides information on the physiological status of the tissue following ICAS analysis. However, caution must be observed to minimize equipment-induced artifacts during image acquisition and analysis.

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G.W. Stutte and C.A. Stutte

Computer analysis of airborne, broad-band, near-infrared (NIR, 710 to 1100 nm) video imagery of peach tree canopies was used to determine spatial variability of cumulative stress in two peach orchards. A significant quadratic correlation was found between leaf-N content and the normalized mean pixel intensity (MPI) of the digital imagery of NIR canopy reflectance. This correlation was used to establish MPI estimates of N-stressed trees in the orchard. The relationship was used to localize site-specific spatial variability in a commercial peach orchard. The underlying soil type was found to be closely associated with the spatial variability in NIR imagery in the commercial peach orchard. Assessing spatial variability in the orchard with NIR video permits early localization of potentially low productivity regions within an orchard.

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G.W. Stutte and J. Gage

Seed coats of developing fruit of peach [Prunus persica (L.) Batsch cvs. Redkist, Redskin, and Loring] were punctured at 31, 33, and 38 days after full bloom (DAFB), respectively. Injections of water, 390 mg GA3/liter, or 390 mg GA4+7/liter were made immediately following seed puncture. Seed puncture and water injection following puncture resulted in abscission of all fruit. Injection of GA3 and GA4+7 delayed abscission of `Redkist' and `Redskin' fruits of punctured seeds by 6 to 10 days. Both GA treatments resulted in normal growth into Stage II and increased fruit retention through Stage III in `Loring'. About 100 μl of 250, 500, or 1000 mg GA3/liter was injected into the locule of `Loring' fruits following seed puncture at 30, 40, or 50 DAFB. GA treatments at 30 DAFB resulted in≈ 75% fruit set in comparison to seeded control fruit, while fruit treated at 40 and 50 DAFB abscised by the end of Stage II. Increasing GA concentration from 250 to 1000 mg·liter-1 had no additional effect. Movement of the GA was examined by injecting 3H-GA1 into the locule following the puncture treatment. More than 97% remained in the fruit after 96 hours. The percentage of 3H recovered in the seed cavity decreased over time, whereas recovered label increased in both endocarp and mesocarp. The results suggest a potential regulatory role for seed-produced gibberellins during early Stage I of development. We have identified an apparent change in tissue sensitivity to gibberellin induction of seedless fruit development between 30 and 40 DAFB in `Loring' peach.

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N.C. Yorio and G.W. Stutte

An experiment was conducted in the Biomass Production Chamber (BPC) at Kennedy Space Center to examine the effects of using continuously reused nutrient solution in an NFT system to support potato growth in batch and continuous planting scenarios. Tuberization was hastened and plant growth reduced on plants grown in the aged nutrient solution. We have previously reported that the effect is removed when the aged nutrient solution is filtered through activated charcoal. In order to investigate this apparent plant growth regulator response, an in vitro bioassay has been developed that allows for repeatable, small scale, and rapid testing of the tuber-inducing response. The bioassay is a liquid culture system that employs 600-mL Berzelius beakers capped with modified Sun transparent tissue culture bags, a light shield around the root zone, and a polyurethane foam support, which holds a micropropagated potato plantlet. With this bioassay, we have observed the same plant stunting and tuber initiation effects that were previously seen with the aged nutrient solution. The bioassay appears to be sensitive to environmental factors (PPF, photoperiod, and temperature) that influence tuberization. In addition, partially purified preparations of the apparent growth regulators have elicited the tuberization response. Currently, efforts are underway to examine the role of the microbial community associated with the BPC nutrient delivery system on the tuberization response.

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G.W. Stutte and N.C. Yorio

The relationship between whole canopy and single leaf measurements of gas exchange has not been well documented. Two experiments were conducted in the Biomass Production Chamber at Kennedy Space Center (20-m2 growing area) to compare whole canopy versus single leaf net carbon assimilation rate (Anet) measurement of a stand of tomato (Lycopersicon esculentum Mill. cv. Reimann Philipp) and soybean [Glycine max (L.) Merr. cv. Hoyt]. Both crops were grown under a 12/12 hour photoperiod under HPS lamps at PPF of 800 (mol·m–2·s–1, at 26/22°C (light/dark), and constant 65% RH for 90 days. CO2 concentration was controlled to 1200 (mol·mol–1 during the light cycle. Midday measurements of Anet of single leaves were obtained weekly from upper canopy leaves using a portable photosynthesis system. Whole canopy measurements of Anet were calculated daily from CO2 addition data obtained at 5-minute intervals by the BPC monitoring and control system. Single leaf rates exceeded whole canopy rates prior to full canopy coverage then averaged 0.63 of whole canopy for both species during the period of full canopy coverage. Results suggest that reliable estimates of canopy gas exchange can be obtained from single leaf measurements under relatively constant environment conditions.

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John D. Lea-Cox, G.W. Stutte, and W.L. Berry

The maintenance of pH in unbuffered nutrient solutions has important consequences for the hydroponic industry and proposed nutrient delivery systems for plants in space. The requirement for charge balance by a model plant system, dwarf wheat (Triticum aestinum cv. Yecora rojo), is largely a function of the uptake ratio of four cation species (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}, Ca2+, and Mg2+) and two anion species (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{SO}_{4}^{2-}\) \end{document}) up to anthesis. The change in electrical conductivity (EC) and pH of the nutrient solution over time integrates the overall influx:efflux process of the plants. Solutions with three different NH4:NO3 ratios were sampled at 15-min intervals over a 12-h period at 9, 10, 16, 17, 23, 24, 37, and 38 days after planting. Exhaustion of N in the solution at all stages of ontogeny resulted in a 2- to 3-fold reduction in ΔpH/Δt, despite high plant tissue N and irrespective of the concentration of other charge balance ions in solution. These data, combined with a plant nutrient uptake database (normalized for plant relative growth rate per mole PPF), suggest that a system can be developed to control pH by direct supply of various alternative nutrient stock solutions, rather than by the addition of H+ or OH from acid or base.

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G.W. Stutte, N.C. Yorio, and R.M. Wheeler

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.

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G.W. Stutte, I. Eraso, S. Anderson, and R.D. Hickey

A series of experiments were conducted to determine the sensitivity of radish to four light alcohols (ethanol, methanol, 2-propanol, and t-butanol) identified as atmospheric contaminants on manned spacecraft. Radish (Raphanus sativus L. `Cherry Bomb' Hybrid II) seedlings were exposed for 5 days to concentrations of 0, 50, 100, 175, 250, and 500 ppm of each alcohol and the effect on seedling growth was used to establish preliminary threshold response values. Results show a general response-pattern for the four alcohol exposures at threshold responses of 10% (T10), 50% (T50) and 90% (T90) reduction in seedling length. There were differences in the response of seedlings to the four alcohols, with the T10 for t-butanol and ethanol (25 to 40 ppm) being 3 to 5× lower than for methanol or 2-propanol (110 to 120 ppm). Ethanol and t-butanol exhibited similar T50 values (150 to 160 ppm). In contrast, T50 for methanol (285 ppm) and 2-propanol (260 ppm) were about 100 ppm higher than for ethanol or t-butanol. Chronic exposures to 400 ppm t-butanol, ethanol or 2-propanol were highly toxic to the plants. Radish was more tolerant of methanol, with T90 of 465 ppm. Seeds did not germinate at the 500 ppm treatment of t-butanol, 2-propanol, or ethanol. There were significant differences in projected performance of plants in different environments, dependent upon the regulatory guidelines used. The use of exposure guidelines for humans is not applicable to plant systems.

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Miklos Faust, Dehua Liu, Merle M. Millard, and G.W. Stutte

Intact apple (Malus domestica Borkh.) buds were examined by magnetic resonance imaging (MRI). MRI did not excite water in unchilled apple buds and could not image it. When chilling was satisfied, images were produced. We interpret this difference to mean that water is in bound and/or structured form in dormant apple leaf buds before the chilling requirement is satisfied. Conversion of bound to free water occurred equally in the low-chilling-requirement cultivar Anna and the high-chillingrequirement cultivar Northern Spy only after 600 and 4000 hours of chilling, respectively. It appears that processes involved in satisfying chilling requirement are also converting water in buds from bound to free form. Absence of free water in dormant buds during the winter signifies endodormancy, whereas when the water is in free form, buds are ecodormant. Thidiazuron, a dormancy-breaking agent, applied to partially chilled buds is instrumental in converting water to the free form within 24 hours. Summer-dormant buds contain free water, and they could be classified only as paradormant. Based on proton profiles, ecodormant and paradormant buds cannot be distinguished but endodormant buds can be readily identified.

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G.W. Stutte, I. Eraso, and E.C. Stryjewski

The RASTA (Radish Assimilation in Spaceflight Testbed Atmospheres) space flight experiment is being designed to evaluate effects of spacecraft environment on carbon partitioning in radish. Carbon dioxide concentration and air temperature effects on radish partitioning are being evaluated to optimize conditions on orbit. Determining effects of these stresses on growth will allow environmental stress effects to be isolated from microgravity effects during the mission. Three cultivars, Cherriette, Cherry Belle, and Early Scarlett Globe, have been grown at 23 °C at 400, 1500 and 10,000 ppm CO2 to determine effects of super-elevated CO2 on growth. Total biomass production was greatest at 1500 ppm CO2, with a decline at 10,000 ppm CO2. Harvest index of all cultivars was also highest at 1500 ppm. `Cherry Belle' and `Early Scarlet Globe' were grown at ambient CO2 under temperatures ranging from 18 to 30 °C. Total biomass production was greatest at 22 °C, with significant declines in total dry mass and harvest index with increasing temperatures. Temperatures less than 22 °C resulted in decrease in total biomass, but partitioning to storage roots was enhanced. (Supported by NASA NCC10-0034)