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Acta Agronomica Hungarica
Authors: P. Almeida, L. Dinis, J. Coutinho, T. Pinto, R. Anjos, J. Ferreira-Cardoso, M. Pimentel-Pereira, F. Peixoto, and J. Gomes-Laranjo

Studies on gas exchange parameters were made at different temperatures and radiation levels in seven seedling populations of chestnut cultivar Judia from different parts of the Trás-os-Montes region, Portugal. Differences were found for the optimal temperature, which was 31°C for JD7, 31.5°C for JD5, 32°C for JD2, 32.5°C for JD4, 33°C for JD3 and JD6, and 33.5°C for JD1 and the ink-resistant hybrid BRO310. At these values, rates of photosynthesis ranged between 8.7 and 13.4 mmol CO 2 m −2 s −1 for JD6 and JD7, while the light conditions allowing 90% of maximal photosynthesis varied between 650 (JD6) and 1385 (JD4) μmol m −2 s −1 . JD1 showed the highest value of leaf water potential, −0.35 Mpa, and JD6, JD7 and BRO310 the lowest, −0.65 Mpa. JD1 also showed the second lowest stomatal conductance (93 mmol m −2 s −1 ) and transpiration rate (3.0 mmol H 2 O m −2 s −1 ).In relation to the photosynthetic pigments, JD3 and JD7 were the most sun-loving clones having the highest values for the Chl a / b ratio (3.2 and 3.3, respectively), while JD1 had the lowest Chl/Car ratio (3.9). The overall results suggested that the JD3, JD1 and JD5 populations might increase heat stress tolerance in Judia.

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