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Amots Hetzroni, Denys J. Charles, and James E. Simon

A nondestructive electronic sensory system (electronic sniffer) that responds to volatile gases emitted by fruit during ripening was developed. It is based upon a single semi-conductor gas sensor placed within a rigid plastic cup equipped with a gas inlet to flush the head between samples. This gas sensor reacts with the range of reductive gases such as the aromatic volatiles that are naturally emitted by the ripening melon fruit. The sensor cup is placed on the exterior of the fruit and the change in electrical conductivity is recorded. In 1994, we examined the electronic sniffer as a tool to nondestructively determine ripeness in `Superstar', `Mission', and `Makdimon' melons. Fruits were manually classified into five ripeness stages based on external appearance and slip stage. Melons were first sampled nondestructively for color, weight, size, and slip stage, and then subjected to the electronic sniffer. Then, fruit volatiles, flesh firmness, and total soluble solids were measured. The electronic sniffer was able to accurately classify melons into three ripeness classes: unripe, half-ripe, and ripe for `Superstar' and `Mission'. The sniffer was only able to separate ripe from over-ripe in `Makdimon', which is known to become over-ripe and deteriorate rapidly. Using the sniffer as a tool to nondestructively measure ripeness and its potential application in fruit quality will be discussed.

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Amots Hetzroni, Denys J. Charles, Jules Janick, and James E. Simon

A prototype of a nondestructive electronic sensory system (electronic sniffer) that responds to volatile gases emitted by fruit during ripening was developed. The electronic sniffer is based upon four semiconductor gas sensors designed to react with a range of reductive gases, including aromatic volatiles. In 1994, we examined the potential of using the electronic sniffer as a tool to nondestructively determine ripeness in `Golden Delicious' and `Goldrush' apples. Fruit were harvested weekly from 19 Sept. to 17 Oct. (`Golden Delicious') and 27 Sept. to 18 Nov. (`Goldrush'). Each week, apples of each cultivar were evaluated individually for skin color, weight size, and headspace volatiles. Each fruit was then evaluated by the electronic sniffer, and headspace ethylene was sampled from air within the testing box. Individual fruits were then evaluated for total soluble solids, firmness, pH, total acidity, and starch index value. The electronic sniffer was able to distinguish and accurately classify the apples into three ripeness stages (immature, ripe, and over-ripe). Improved results were obtained when multiple gas sensors were used rather than a single gas sensor.

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D.J. Makus

The performance of two sweet corn (Zea mays var. saccharata) cultivars grown in the Rio Grande Valley in Spring 1997 were evaluated under three tillage practices. On 25 Apr. 1997, `Champ' and `Sensor' seeds were sown on 0.76-m row centers of 4.6 x 91-m (12 x 300-ft) plots which had been in continuous conventional (CT), minimum tillage (MT), and/or no tillage (NT) since Aug. 1994. All production inputs were similar except tillage practice. Ears were harvested beginning 16 Jun 1997. Cultivars differed in leaf greenness, plant stand (P < 0.11), ear diameter, length, and dry matter, percentage of total yield at first harvest, season yield, and ears/ha. `Sensor' ears had higher concentrations (dry-mass basis) of total N, K, S, NO3, and B, but lower concentrations of Mg (P < 0.06), Ca, Fe, and Mn than did `Champ'. Amaranthus spp. weed populations were higher in `Champ' then in `Sensor' tillage treatments. MT and CT resulted in greater ear attributes, yield, ears/ha, and less corn earworm damage, lower ear S concentrations, and fewer total weeds/ha than corn grown with NT. Plant stand was highest in CT plots. Weed populations of Panicum and Amaranthus spp., but not Texas tridens [Tridens texanus (S. Wats.) Nash] or common purslane (Portulaca oleracea L.), were higher in NT-grown corn than MT- or CT-grown corn.

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Karthik-Joseph John-Karuppiah and Jacqueline K. Burns

response sensor 1 ( CsERS1 ), ethylene response 1 ( CsETR1 ), 2 ( CsETR2 ), and 3 ( CsETR3 ), constitutive triple response 1 ( CsCTR1 ), ethylene insensitive 2 ( CsEIN2 ), ethylene insensitive 3-like 1 ( CsEIL1 ) and 2 ( CsEIL2 ), and glyceraldehyde 3

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Rita Giuliani, Eugenio Magnanini, and Luca Corelli Grappadelli

This work proposes a methodology, by light-scanning below the canopy, to directly estimate the photon flux radiation (400–1200 nm) intercepted by single or row canopies. The system is based on the assumption that the light intercepted by the canopy, at a particular time, corresponds to the difference between the incoming potential radiation on a ground surface area (able to include the ground area shaded by the canopy), and the actual radiation influx to that area in presence of the canopy. To this purpose, light-scanning equipment has been designed, built, and tested, whose main components are two aligned multi-sensor bars (1.2 m long) and a CR10 data logger, equipped with an AM 416 Relay Multiplexer (Campbell Sci. Ltd., U.K.). The radiation sensors (BPW 14N TELEFUNKEN) were chosen because of their spectral sensitivity, along with low cost. The sensors have been placed along the bars, at 5-cm intervals, and fitted with a Teflon® diffuser to provide a cosine correction. Radiation measurements are taken moving parallelly the bars on the ground, step by step, to monitor a sample point grid (5 cm by step length). Preliminary radiation scans were taken during the summer in a 3-year-old peach orchard, trained as delayed vasette. Measurements were taken for a single canopy at various hours of the day. Moreover, radiation scans were taken at the same hour, over a 3-day timespan, while gradually defoliating the canopy. A custom-built software program has been developed for data handling. Mathcad software (Mathsoft Inc., U.S.) has been used to display the canopy shade image projected on the ground, the quantum map of the monitored area, and to calculate the light influx on the whole canopy. Moreover, the light spots on the ground determined by foliage gaps have been identified and the amount of radiation reaching the ground has been be estimated.

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D.J. Makus

In Spring 1998, two sweet corn (Zea mays var. rugosa) cultivars were grown under three tillage systems, conventional cultivation, ridge tillage (RT), and no tillage (NT), which had been in continuous management since Fall 1994. Nitrogen (as NH4NO3), the only fertilizer used, was applied twice at 60 kg/ha. Sweet corn yields were not influenced by tillage system, but average ear weights tended to be smaller under NT (P < 0.17). Ear quality attributes, which included ear weight, length, diameter, dry matter, and incidence of earworm damage, were greater in the later-maturing `G-90' cultivar than in `Sensor'; but tillage system had no influence on these attributes. Cultivars supported different weed species underneath their canopies. `Sensor' allowed more light penetration and sustained higher weed biomass than did the taller `G-90' plants. Weed biomass was higher under RT and NT. Seasonal soil moisture was lowest in the RT plots, but only in the 0- to 15-cm profile. Soil temperatures (unreplicated) at the 15-cm depth were similar between cultivars and tillage treatments over the growing season. The earlier-maturing `Sensor' generally accumulated more ear mineral nutrients (P, S, NO3, Ca, Na, Zn, Mn, Al, and B; dry weight basis), but had lower dry matter (percentage) than did `G-90'. Cumulative nutrient levels tended to be lowest in NT-grown ears (P < 0.08). Soil sampled at 0- to 5-, 10- to 15-, and 25- to 30-cm depths generally had higher concentrations of nutrients toward the surface, and NT soils had the steepest nutrient gradients, with the exception of Na and NO3. Total soil salts were reduced by RT and NT, but C: N ratio remained unchanged between tillage systems.

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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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Rico A. González, Daniel K. Struve, and Larry C. Brown

An irrigation control system has been developed and used to estimate evapotranspiration of contamer-grown plants by monitoring randomly selected plants within a container block and watering on an “as needed” basis. Sensor reliability and operational ease allows application of the system in a wide variety of field conditions. First-year tests, using red oak (Quercus rubra L.) seedlings, showed a reduction of 95% or better in both total irrigation and leachate rates with the computer-controlled treatment relative to a manually controlled, drip irrigation treatment without reducing plant growth.

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Steven H. Schwartzkopf

The use of computerized environmental control systems for greenhouses and plant growth chambers is increasing in frequency. Computerized systems provide the potential for more accurate environmental control, while at the same time allowing changes to be made more easily than with hard-wired mechanical control systems. The ease of changing allows switching sensor types, relocating sensors and resetting control parameters without significantly affecting the overall system design. Another advantage of computerized control systems is that they provide a method for recording environmental data as they simultaneously implement their programmed control algorithms. This data can subsequently be transferred to other computers for further processing and analysis. Computerized controls also support the possibility of implementing environmental control based on either mathematical models which simulate plant growth, or on actual monitored plant performance data such as nutrient uptake or leaf temperature. This paper discusses in detail these and other advantages of using computerized environmental control systems, as well as describing the problems and disadvantages associated with their implementation and use.

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Mark A. Rose, John W. White, and Joel L. Cuello

Recently developed stem flow gauges that allow for direct, accurate, non-invasive, and continuous measurement of plant sap flow rates have not been used to monitor transpiration of floricultural plants grown in greenhouses.

A Dynamax SGA10 heat-balance sap-flow sensor was mounted on a potted rose plant's main stem containing a total leaf area of 0.52 m in order to monitor transpiration. The sensor was connected to a CR21X Micrologger for data calculation and temporary storage. The results showed average midday sap-flow rates range from 20-30 g·hr-1 to 50-70 g·hr-1 at low and high levels of PPF, respectively. Nighttime levels of 4-7 g·hr-1 persisted throughout early winter trials. Monitoring transpiration of the same rose stem using a lysimeter revealed a significant linear correlation (r2 = 0.999) between the lysimeter and the stem flow gauge values.

In the future, research will be conducted with the gauge to investigate relationships between microclimatic variables, photosynthesis, and transpiration.