A comparison of photosynthetic gas exchange parameters measured under in situ and in vitro conditions in Pinus nigra subsp. pallasiana and Pinus brutia trees

Abstract

This study was conducted to compare the results of in situ and in vitro methods that can be used for measuring gas exchange parameters in two pine species. The study was carried out in a mixed Pinus nigra Arn. subsp. pallasiana (Lamb). Holmboe and Pinus brutia Ten. plantation in Kemer/Burdur, which has a semi-arid climate type located in the Western Mediterranean Region of Türkiye. In the first method, gas exchange parameters (net photosynthetic rate-Anet, stomatal conductance-gs and transpiration rate-E) were measured directly on the tree using a mobile scaffold to reach to the tree canopy (in situ conditions). In the second method, branches were cut at approximately 50 cm and gas exchange parameters were determined in the same needles after the branch was immediately submerged in water (in vitro conditions). Measurements were taken between June and October 2022. Student’s t-test was conducted to compare the results of in situ and in vitro photosynthesis measurement methods. No statistically significant differences were found between the results of the compared methods in terms of gas exchange parameters for both species. The results of the study showed that in vitro measurements of photosynthesis can be preferred to in situ measurements of photosynthesis in P. nigra and P. brutia under field conditions where access to the canopy of tall trees is not possible.