Photosynthetic light response curves in Eucalyptus benthamii and Eucalyptus dunnii clones

Abstract

The photosynthetic light-response curve reflects the instantaneous response of the net photosynthetic rate to different gradients of photosynthetically active radiation. Genetic materials can respond differently to light and consequently alter productivity. Thus, this work aimed to compare clones of Eucalyptus benthamii and Eucalyptus dunnii by checking the CO2 assimilation rate due to the increase in photosynthetically active radiation. The evaluations were carried out in mini-stumps implanted in a clonal mini-garden system. The CO2 assimilation rate curves were determined with the aid of a portable photosynthesis meter. The curves of CO2 assimilation rate (A) in response to the increase in photosynthetically active radiation (PAR) were evaluated at values of 1500, 1000, 700, 450, 250, 120, 50 and 0 μmol m-2 s -1 for clones of E. benthamii and E. dunnii. The three Eucalyptus clones evaluated showed a similar behavior of the A/PAR curve, showing a high demand for photosynthetically active radiation. In general, the three clones were very similar in terms of CO2 assimilation rate due to the increase in photosynthetically active radiation.