Title: Reflective films and expression of light-regulated genes in field-grown apple Authors
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 2014
Publication Date: N/A
Interpretive Summary: Reflective films are used in orchards to control excessive water loss and to develop good fruit coloration. Although measurements of photosynthesis have shown that particle films do not inhibit photosynthesis, no one has looked at the expression of genes associated with the light and dark reactions of this process. We examined leaves from apple (‘Empire’) trees which had been collected in the late morning in full sunlight. Most of the photosynthesis genes we examined were not affected by the particle film, whereas some of the genes were not as active when an aluminized plastic film was used. Only one gene was more active under the plastic film, and this gene is more associated with high light damage than photosynthesis. This study provides another type of measurement demonstrating the efficacy of reflective particle film in orchard management.
Technical Abstract: Reflective films are used in orchard management to improve fruit coloration. Numerous physiological studies on the effects of application of these films have been conducted, including variation of angles of light incidence and reflection, spectral determination of reflected light and effects on photosynthesis and pigment development. At present, there have been no studies on the effects of these treatments on gene expression, particularly with regard to genetic factors controlling light perception and genes targeted by specific regulators. We sampled a fully developed leaf from apple (Malus x domestica Borkh.) branches of mature trees in two consecutive years. The grass middle between the tree rows was left untreated, sprayed with a formulation of a reflective particle film (RPF) or covered with a single layer of an aluminized plastic film (APF). Leaves at the same branch position were sampled between 10am and 12pm on sunny days. Nine different gene transcripts associated with light perception, sorbitol transport and actin (MdAct; control) were measured by sqRT-PCR and five by qRT-PCR. Most of the gene activity was unaffected by treatment or slightly enhanced by RPF. However, the levels of several genes, including MdPif3, MdPhyB and MdSot3, were reduced by application of the APF. Only one gene, MdElip1A/B, was significantly and dramatically elevated by APF. The results of the RPF treatment are consistent with earlier observations indicating that application of this film to the tree canopy has little effect on photosynthesis.