Are Wild Blueberries a Crop with Low Photosynthetic Capacity? Chamber-Size Effects in Measuring Photosynthesis

Abstract

Wild lowbush blueberries, an important fruit crop native to North America, contribute significantly to the economy of Maine, USA, Atlantic Canada, and Quebec. However, its photosynthetic capacity has not been well-quantified, with only a few studies showing its low photosynthetic rates. Its small leaves make accurate leaf-level photosynthetic measurements difficult and introduce potential uncertainties in using large leaf chambers. Here, we determined the photosynthetic rate for five different wild blueberry genotypes using a big leaf chamber enclosing multiple leaves and a small leaf chamber with a single leaf to test whether using big leaf chambers (branch-level measurements) underestimates the photosynthetic capacity. Photosynthetic rates of wild blueberries were significantly (35–47%) lower when using the big leaf chamber, and they are not a crop with low photosynthetic capacity, which can be as high as 16 μmol m−2 s−1. Additionally, wild blueberry leaves enclosed in the big chamber at different positions of a branch did not differ in chlorophyll content and photosynthetic rate, suggesting that the difference was not caused by variation among leaves but probably due to leaf orientations and self-shading in the big chamber. A significant linear relationship between the photosynthetic rate measured by the small and big leaf chambers suggests that the underestimation in leaf photosynthetic capacity could be corrected. Therefore, chamber-size effects need to be considered in quantifying photosynthetic capacity for small-leaf crops, and our study provided important guidelines for future photosynthesis research. We also established the relationship between the Electron Transport Rate (ETR) and photosynthetic CO2 assimilation for wild blueberries. ETR provides an alternative to quantify photosynthesis, but the correlation coefficient of the relationship (R2 = 0.65) suggests that caution is needed in this case.

Are Foliar Fertilizers Beneficial to Growth and Yield of Wild Lowbush Blueberries?

“…Our study observed leaf photosynthetic rate variation of 1 to 3 µmol.m −2 s −1 across different treatments with different genets in the studied field. This is consistent with the previous study [2] conducted in the same field, which has shown high variation (range of 2 to 5 µmol.m −2 s −1 ) in leaf photosynthetic capacity across different wild blueberry genets. Average leaf surface area per stem was higher in SeaCrop16 and DAP treatments (although not significant), possibly because of the cell division regulator hormone (cytokinin) in SeaCrop16 and the high nitrogen supply from the DAP fertilizer [5,32].…”

“…This is because leaf photosynthetic rates measured in this study did not follow the trend of the measured leaf chlorophyll concentration, and hence there was no correlation or relationship between these two physiological traits. Two treatments (DAP, SeaCrop16) showed lower, and other treatments showed similar leaf photosynthetic rates to the control plot, which might be because of high variation in photosynthetic capacity across genets [2]. Our study observed leaf photosynthetic rate variation of 1 to 3 µmol.m −2 s −1 across different treatments with different genets in the studied field.…”

“…An individual wild blueberry plant, with its spreading rhizome system, is referred to as a genet [1]. Each genet is visually, genetically, and physiologically different [1,2] from neighboring plants creating a complex mixture of genets in the wild blueberry fields, which provides consumers with a rich diversity of flavors. This crop is managed in a two-year cycle: the plants grow vegetatively in the first year (vegetative year) after the harvest and pruning of the previous year, and the plants flower and produce fruits in the second year (crop year).…”

“…Additionally, the physiology of wild blueberries is relatively understudied. Few studies, to our knowledge, have explored the photosynthetic performance of this crop [2,[20][21][22][23][24]. Also, no study so far has related the wild blueberry photosynthesis and other physiological and morphological traits to fruit yield.…”

Influence of Probable Precipitation Futures on Strawberries (Fragaria x ananassa): Results from a Simulated Rainfall Experiment

“…Variables measured included the quantum yield of photosystem II (Y(II)), which equals Fv/Fm, and is sensitive to stress. We also assessed the electron transport rate (ETR), which indicates actual photosynthetic performance under specific light conditions and is related to photosynthetic CO2 assimilation [30]. Both Y(II) and ETR were measured weekly from 12:00 to 4:00 pm using a FluorPen portable leaf fluorescence meter (Photon Systems Instruments, Drásov, Czech Republic).…”