A comparison of methods for excluding light from stems to evaluate stem photosynthesis

Abstract

PremiseA comparison of methods using different materials to exclude light from stems to prevent stem CO2 exchange (i.e., photosynthesis), without affecting stem conductance to water vapor, surface temperature, and relative humidity, was conducted on stems of avocado trees in California.Methods and ResultsThe experiment featured three materials: aluminum foil, paper‐based wrap, and mineral‐based paint. We examined stem CO2 exchange with and without the light exclusion treatments. We also examined stem surface temperature, relative humidity, and photosynthetic active radiation (PAR) under the cover materials. All materials reduced PAR and stem CO2 exchange. However, aluminum foil reduced stem surface temperature and increased relative humidity.ConclusionsMethods used to study stem CO2 exchange through light exclusion have historically relied on methods that may induce experimental artifacts. Among the methods tested here, mineral‐based paint effectively reduced PAR without affecting stem surface temperature and relative humidity around the stem.

The benefits of woody plant stem photosynthesis extend to hydraulic function and drought survival in Parkinsonia florida

“…The surviving 22 two-year-old P. florida saplings were randomly assigned to two groups of 11 plants each: group 1 (‘wrapped’) consisted of plants with their stems loosely covered with aluminum foil that effectively blocked light transmission (100% light exclusion) but allowed gas exchange, and group 2 (‘control’) consisted of plants without light exclusion ( Figure S2 available as Supplementary data at Tree Physiology Online). Stem surface temperature is relatively lower and relative humidity (RH) higher under the aluminum foil than in control plants, but this does not affect gas exchange values ( Valverdi et al. 2023 ).…”

“…Stem surface temperature is relatively lower and relative humidity (RH) higher under the aluminum foil than in control plants, but this does not affect gas exchange values ( Valverdi et al. 2023 ). We started wrapping the stems in the ‘wrapped’ group on 25 April 2017 (day of year, DOY, 115) and ended on 10 May 2017 (DOY 130) because of the extensive branching of the plants that required detailed wrapping.…”