Gene A Giacomelli

PMID: 11541685;Abstract:

The tomato plant was used as a model to study growth and movement due to temperature changes in the environment. A morphological feature, plant top projection canopy area (TPCA), was used to characterize the plant growth and movement. Three temperature regimes (normal temperature, low temperature, and a step change from normal to low temperature) were used for the study. It is found that the plants have significant cyclic canopy movement. In addition, both plant growth, which is represented by canopy expansion, and canopy movement are affected by air temperature. The response of the plant to a step change of air temperature was also documented.

Abstract:

Recently in some large scale greenhouses, young tomato seedlings have been planted between mature crop rows to enable year-round production. Young seedlings receive light intercepted and transmitted/reflected by leaves of mature crops. Light quality (spectrum) changes by these procedures and affects the seedling growth. In particular, red/far red ratio is of main concern, because this ratio affects the stem extension rate via the change in the phytochrome photostationary state (Pfr/Ptotal)-However, there have been no reports on the light quality in and between tomato crop rows. Measurements of light quality in and between mature tomato crop rows were conducted in a semi-arid greenhouse in Tucson, Arizona on a clear day and profiles of R/FR ratio and Pfr/Ptotal were calculated. When the direct solar radiation penetrated into the canopy in parallel to the row, photon flux density (PFD) in FR at the height of 2.20 m in the passage between the rows was larger than that at the canopy height (3.10 m). Gradual decrease of R/FR with the depth into the canopy was observed in the passage, but in the rows, R/FR took the minimum value at the middle of the height. In the passage, Pfr/Ptotal was almost constant with regard to the height when the direct solar radiation ran parallel to the row, but at other periods slightly decreased with the depth into the canopy from 0.7 at the canopy height to 0.6 at the ground. In the rows, Pfr/Ptotal took the minimum at the middle of the height.

Abstract:

This study was conducted to determine the effects of vent configuration and external wind speed on three-dimensional distribution of air temperature in a naturally ventilated multi-span greenhouse using wind tunnel experiments. The experiments were conducted with the scale models in a wind tunnel with four different vent configurations and at four external wind speeds ranging from 0 to 3 m/s at full scale, with 1 m/s increments. Three dimensional temperature distributions were analyzed and the airflow patterns were observed based on temperature distributions. The highest air temperatures were found to be in spans close to the leeward side vent when the side vents were closed at zero wind speeds in the case when the roof vents were fully open and side vents were closed. The air temperature, measured by thermocouples, was higher on the windward side of the greenhouse than on the leeward side for all wind speeds when only roof vents were used. The distribution of air temperature was more uniform when both side and roof vents were used. As the wind speed increased, the average internal air temperature decreased for all cases. Contribution of side vents for greenhouse ventilation and reduction of air temperature were significant for the particular greenhouse design used in this study.

Abstract:

The development of a computer simulation model for greenhouse tomato crop management is discussed. The management model, based on a crop production model, will determine a production schedule designed to provide a continuous yield, optimize greenhouse space utilization, and predict production rates throughout the year.

Abstract:

The availability of solar radiation in a bow-type, air-inflated, double polyethylene covered greenhouse was studied. Solar total radiation (0.285 to 2.8 μm waveband) transmittance and the transmittance of photosynthetically active radiation (solar PAR, 0.4 to 0.7 μm) were compared. The comparisons were reported for measurements made both at the glazing and the plant canopy levels. A relationship was previously determined for the available solar total radiation (W m^-2) and solar PAR (μmol s^-1 m^-2), transmitted through the atmosphere. This report focuses on the effects of glazing and structure on transmitting ambient solar radiation and the development of a relationship for transmittance of solar total radiation (W m^-2) versus solar PAR (μmol s^-1 m^-2) between the two wavebands.