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Gary W. Stutte

A digital video camera (Panasonic Industrial Co., Secaucus, NJ) with a 1.7 cm charged coupled device detector (574 (h) × 499 (v) pixel elements) was modified with a custom made FRF-700 band pass filter to visualize canopy reflectance in the near-infrared (NIR) from 700 to 1100 nm. Images of canopy reflectance under a range of environmental stresses were obtained from peach and apple trees under greenhouse and field conditions. Individual video frames were digitized with Image Capture and Analysis System (Agri Imaging Systems, Inc., Fayetteville, AR). Image contrast was increased with digital equalization and filtering before classification into one of five stress levels. There was a high correlation (r2 > 0.8) between leaf stress and canopy reflectance in both apple and peach at distances < 5 meters. Spatial variability in stress-induced NIR reflectance could be detected and classified at vertical distances from 150 to 500 M. Analysis of vertical imagery revealed sections of the orchard which were most susceptible to environmental stress.

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Gary W. Stutte

Effective management of site variability has been shown to improve efficiency of chemical use, enhance of fruit quality, optimize irrigations and increase profits. Techniques for localizing and quantifying spatial variation through computer analysis of aerial imagery exist, but the detailed knowledge of soils, site history, and nutrition required for effective management of the variation often are not available in a readily accessible or timely fashion. As a consequence, the benefits of site-specific management have not been fully realized by horticultural managers. These limitations have been partially overcome by developing an information management system which integrates image analysis functions to identify crop stress, a geographic information system to relate stresses to resident and nonresident site factors, and custom spreadsheets that provide a cost/benefit analysis of various management decisions. The system allows a manager to visualize the probable impact of an intervention on variability, yield, and profits in a timely manner.

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Gary W. Stutte

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Gary W. Stutte

The use of light-emitting diodes (LEDs) to support plant growth is a radical departure from use of gas-discharge lamps, which were developed in mid-19th and widely adopted by the industry during the 20th century. Initial investigation by the National Aeronautics and Space Administration (NASA) in the late 1980s on the use of LEDs to grow plant in space is resulting in an industry-wide transition from gas discharge to solid-state lighting systems. This global transformation is given urgency by national policies to reduce energy consumption and being facilitated by ready access to information on LEDs. The combination of research, government policy, and information technology has resulted in an exponential increase in research into the use and application of LED technology in horticulture. Commercial horticulture has identified the opportunities provided by LEDs to optimize light spectra to promote growth, regulate morphology, increase nutrient content, and reduce operating costs. LED-light technology is enabling the development of innovative lighting systems, and is being incorporated into large-scale plant factories for the production of edible, ornamental, and medicinal plants. An overview of prevalence of readily accessible information on LEDs and implications for future adoption in horticulture is discussed.

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Gary W. Stutte

NASA has investigated the use of recirculating nutrient film technique (NFT) systems to grow higher plants on long-duration space missions for many years and has demonstrated the feasibility of using recirculating systems on numerous crop species. A long duration (418-day) experiment was conducted at Kennedy Space Center, Fla., to evaluate the feasibility of using recirculating hydroponics for the continuous production of Solanum tuberosum L. `Norland'. The productivity of four sequential batch plantings was compared to staggered harvest and plantings. The accumulation of bioactive organic compounds in the nutrient solution resulted in reduced plant height, induced early tuber formation, and increased harvest index of the crops in both production systems. The changes in crop development were managed by increasing planting density and reducing cycle time to sustain production efficiency.

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Gary W. Stutte

Light-emitting diodes (LEDs) are solid-state, long-lived, durable sources of narrow-band light output that can be used in a range of horticultural and photobiological applications. LED technology is rapidly developing and high-quality, high-output LEDs are becoming commercially available at an affordable cost. LEDs provide the opportunity to optimize the spectra for a given plant response, but consideration must be given to both photosynthetic and photomorphogenic effects of light while making those selections. A discussion of basic phytochrome response and data necessary to select narrow-band LEDs to achieve a specific photostationary state is provided. The use of LEDs to alter spectral quality, and phytochrome equilibrium, to regulate anthocyanin formation in red leaf lettuce and to regulate flowering of short-day strawberry are discussed.

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Zhongchun Wang and Gary W. Stutte

Previous results showed that active sorbitol accumulation occurs under water stress. We tested the hypotheses that sorbitol accumulation is due to reduced sorbitol export from leaves or from increased synthesis of glucose to sorbitol. To test the hypotheses, 230 μl 14C-sucrose was introduced through the stems to detached `Jonathan' apple shoots which had either water stress or no stress. Following uptake of 14C-sucrose, 0% or 10% PEG was applied to shoots for 24 hours. The results showed that 73% of 14C-sucrose in non-stressed leaves was broken down within 1 hour and 44% was recovered in sorbitol. PEG initially stimulated the breakdown of 14C-sucrose to glucose and fructose, but further conversion to sorbitol was reduced. However, the percentage of 14C-sorbitol in mature leaves increased gradually in 10% PEG until it exceeded that of control at 24 hours. In contrast to mature leaves, young leaves and stems showed significantly less sorbitol under 10% PEG 24 hours after treatment. These results supported the hypothesis that sorbitol accumulation under water stress was due to the reduced sorbitol transport.

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Gary W. Stutte and Greg Goins

In preparation for a spaceflight experiment to measure photosynthesis of wheat (PESTO), four solid media were evaluated for use in the rooting modules of the Biomass Production System (BPS), a new plant growth unit for microgravity. The media were commercial peat-vermiculite (PV) mixture, zeolite developed at Johnson Space (Z/JSC), commercial zeolite developed by Boulder Innovative Technologies (Z/BIT), and arcillite (AR) with slow-release fertilizer. Wheat (cv. USU Super Dwarf) was grown in the media at 1500 μmol/mol CO2, 350 μmol·m-2·s-1 PAR, 23 °C, and 75% relative humidity for 18 to 21 days. Water was delivered to the media through porous tubes imbedded in the media, and NDS pressures of -0.1 to -0.5 kPa were maintained with either a static or recirculating standpipe. Plant height, leaf area, and fresh mass were determined for each experiment. Results indicated that the AR and Z/BIT media resulted in larger and more uniform plants than Z/JSC or PV at the same NDS pressure. Additional experiments were conducted with AR to evaluate interactions between particle size and NDS pressure. At ≈14 days after planting, there was a loss of NDS prime in AR >2.0 mm when the NDS pressure was less than -0.3kPa. This resulted in drying of the media and poor plant growth. There was excess water in the media, which resulted in reduced plant size, in AR <1.0 mm at NDS pressures more than -0.3 kPa.

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Zhongchun Wang and Gary W. Stutte

Greenhouse grown 2-year-old potted `Jonathan' apple trees (Malus domestica Borkh.) were subjected to various levels of water stress in February. Midday leaf water potential (ψW), leaf osmotic potential (ψS), soluble sugars, and starch contents of mature leaves were measured throughout the development of water stress to determine whether active osmotic adjustment could be detected and whether carbohydrates were involved. Active adjustments of 0.6 MPa were observed 3 and 5 days, respectively, after water stress was initiated. Leaf turgor potential (ψP) could not be maintained through the osmotic adjustment when ψW dropped below -1.6 MPa. Sorbitol, glucose, and fructose concentrations increased while sucrose and starch levels decreased significantly as water stress developed, strongly suggesting that sugar alcohol and monosaccharide are the most important osmotica for adjustment. Sorbitol was a primary carbohydrate in the cell sap and accounted for > 50% of total osmotic adjustment. The partitioning of newly fixed W-labeled photosynthates in mature leaves was not affected by water stress immediately after the 30-min 14CO2 treatment. All the W-labeled carbohydrates decreased in the labeled leaves very rapidly after 14CO2 labeling. The decrease in 14C-sorbitol was greater than the decrease in other carbohydrates under both well-watered and stressed conditions. After 24 hours of water stress, however, the percentage of 14C-sorbitol increased while the percentages of sucrose, starch, glucose, and fructose decreased significantly with increasing levels of stress. The ratio of 14C-sorbitol in leaves with ψW = -3.5 MPa to leaves with ψW = -0.5 MPa was significantly higher than that of 14C-sucrose, 14C-glucose, W-fructose, or 14C-starch.

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Oscar Monje, Sylvia Anderson, and Gary W. Stutte

The effect of elevated root zone temperature (+0, +4, +6, +8, and +11 °C) on growth rates and carbon partitioning of ‘USU-Apogee’ spring wheat (Triticum aestivum L.) plants growing at constant air temperature (24 °C) in Turface was investigated. This experiment was performed to determine if wheat growth responded to elevated root zone temperature (RZT) and if so, to determine the temperatures for those responses. The RZT treatments were initiated 5 d after planting (DAP) to prevent RZT effects on germination from affecting results. The effects of increased RZT on development and carbon partitioning were determined from data collected during destructive harvests at 7, 15, 22, and 28 DAP. At a constant air temperature of 24 °C, reduced plant height was observed by 15 DAP at 30 °C RZT (+6 °C), and reduced leaf area was observed by 22 DAP at 28 °C RZT (+4 °C). Changes in leaf photosynthesis and stomatal conductance (g S) were not observed until 35 °C RZT (+11 °C), which was lethal by 22 DAP. Changes in carbon partitioning resulted in decreased leaf mass and increased stem and head mass fractions as well as accelerated development of reproductive structures. Although elevated RZT temperatures above air temperature affected physiological and morphologic parameters, they did not change plant phenology.