Evaluation of Tomato Photosynthetic Potential Based on the Chlorophyll Fluorescence of Leaflets Sealed with Transparent Film or Vaseline

Abstract

When chlorophyll fluorescence is measured on leaves with restricted gas exchange by a transparent film or Vaseline seal, the obtained electron transport rate in photosystem II (J_PSIIseal) was reported show a positive linear correlation with the maximum photosynthetic activity. This is because in a sealed leaf, the CO₂ substrate for ribulose-1,5-bisphosphate-carboxylase/oxygenase is derived primarily from photorespiration. Our objective was to clarify whether the J_PSIIseal also corresponds to photosynthetic activity in tomato leaflets. The J_PSIIseal of a leaflet had a positive linear relationship with the gross photosynthetic rate at 30 mmol mol⁻¹ oxygen. This suggests that the J_PSIIseal represents the photosynthetic carbon fixation activity. Maintaining a tight seal with the transparent film was difficult because of the gap between the film and leaflet during transpiration. In contrast, the tight seal with Vaseline enabled measurements for at least 30 min. Additionally, the measurements could be completed faster for the Vaseline-sealed leaflets. The variation in the J_PSIIseal of tomato leaflets increased with increasing leaf age. The leaf J_PSIIseal (i.e., calculated based on 10–13 leaflets) decreased with increasing leaf age. We propose that chlorophyll fluorescence measurements for Vaseline-sealed leaflets may be useful for comprehensive analyses of tomato leaf photosynthetic characteristics.