Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 9, 2001
Publication Date: N/A
Interpretive Summary: Alternatives to synthetic chemical pesticides are needed to help ameliorate restrictions that are likely to result from legislation such as the Food Quality Protection Act. Hydrophobic particles can deter feeding of fruit-damaging insects such as pear psylla and it is possible that hydrophobic particles can be used to control insects and improve quality of fother fruit and vegetable crops. This research was designed to determine the effect of hydrophobic particles on growth and photosynthesis of bean plants grown in a controlled environment. Bean Plants were grown for 8 weeks in a greenhouse and each week the shoots were sprayed with hydro- phobic particles. Photosynthesis was similar in particle-treated and control bean plants but photosynthesis was slightly higher in particle- treated plants than control plants at high light intensities. At high light intensities, leaf temperatures were reduced by particle treatments. At lower light levels, photosynthesis of particle-treated plants was less than control plants. When large quantities of particles were applied, photosynthesis decreased, probably due to shading by the particle film. In bean plants, excessive particle residues may reduce photosynthesis, particularly at low light levels. However, particle applications may sustain photosynthesis at light intensities above 1/2 of maximum solar radiation by reducing leaf temperature.
Technical Abstract: Bean (Phaseolis vulgaris L.) plants were grown for 8 weeks in a greenhouse and each week the shoots were sprayed with hydrophobic particles. Photo- synthesis was similar in particle-treated and control bean plants. However, when photosynthesis photon flux (PPF) exceeded 670 umol PPF m-2 s-1. photosynthesis was higher in particle-treated plants. At high PPF, leaf temperatures were reduced by particle treatments. At lower PPF, photo- synthesis of particle-treated plants was less than control plants. Root weights of particle-treated plants were smaller than control plants, suggesting that particle films may alter dry weight partitioning. Particle residues on leaves varied with time intervals between particle applications. For example, particle residues on leaves were nearly 3-fold greater for plants treated eight times over 2 days than for plants treated weekly over 8 weeks. In bean, leaf particle residues of 2.71 mg cm-2 contributed to greater photosynthesis at PPF above 670 umol m-2 s-1, but a lower PPF photosynthesis was less than in the control. Leaf particle residues of 7.04 mg cm-2 decreased photosynthesis at high PPF. In bean plants particle applications may sustain photosynthesis at high PPF by reducing leaf temperature, but larger particle residues may reduce photosynthesis, particularly at low PPF.