Effects of water supply on gas exchange in Pinus pinaster Ait. provenances during their first growing season

Abstract

-Gas exchange parameters were monitored during the first growing season on Pinus pinaster young seedlings belonging to six provenances and submitted to two water supply regimes in the open air under cover. Significant differences were found between water supply regimes and measurement dates; sometimes also between provenances. Gas exchange rate responses to needle water potential were similar for all the provenances, and rate changes were only detected as water potential went down to less than -1.3 MPa. The Iberian provenances, in contrast to the Landes, showed a tendency to save water at the end of Spring, which indicates an adaptation to locations with Summer drought. The growth differences between provenances were not expressed in terms of differences in the instantaneous net photosynthetic rate, since this will depend on other factors, such as seedling water status and the time that the measurement was made. However, provenance growth differences may be partially explained by the differences in water use efficiency and nitrogen productivity. maritime pine / early selection / gas exchange parameters Résumé -Effets de l'alimentation en eau sur les échanges gazeux des provenances de Pinus pinaster Ait. au cours de leur première saison de végétation. Les échanges gazeux ont été étudiés au cours de la première saison de végétation de jeunes semis de Pinus pinaster appartenant à six provenances et soumis à deux régimes d'alimentation en eau sous couvert en plein air. Des différences significatives ont été trouvées entre les régimes d'alimentation en eau et les dates de mesures, parfois aussi entre les provenances. Les réponses des taux d'échanges gazeux au potentiel hydrique des aiguilles étaient similaires entre toutes les provenances, et les changements de taux ne furent seulement détectés que lorsque le potentiel hydrique devint inférieur à -1,3 MPa. Les provenances ibériques, contrairement à celles des Landes, montrèrent une tendance à économiser l'eau à la fin du printemps, ce qui indique une adaptation à la situation de sécheresse estivale. Les différences de croissance entre provenances ne se sont pas exprimées en terme de différences de taux nets instantanés de photosynthèse, car cela dépend aussi d'autres facteurs comme le statut hydrique des semis et de l'époque où les mesures ont été effectuées. Cependant, les différences d'accroissements entre provenances peuvent être partiellement expliquées par des différences dans l'efficience d'utilisation de l'eau et de l'azote. pin maritime / sélection précoce / échanges gazeux

Intraspecific variation in growth and allocation patterns in seedlings of Pinus pinaster Ait. submitted to contrasting watering regimes: can water availability explain regional variation?

“…Moreover, when the impact is evaluated on morphological traits and allocation, it denotes similar phenotypic plasticity in response to drought at an intraspecific level. In agreement with interpopulation homogeneity in drought tolerance, Fernández et al (2000) did not find differences among populations in gas exchange variables in seedlings of P. pinaster submitted to contrasting watering regimes. In contrast, intraspecific variation in physiological mechanisms involved in drought tolerance has been reported in three-years-old individuals of this species (Nguyen-Queyrens and Bouchet-Lannat, 2003).…”

Phenotypic plasticity in Pinus pinaster δ13C: environment modulates genetic variation

“…Populations from drier and lower latitudes did not exhibit higher water use efficiency compared to northern and humid latitudes. This could be related to and absence of differences in gas exchange rates (A and g), which was reported for the A and O populations and another population from the French Landes, in two water treatments, by Fernandez et al (2000). In any case, δ 13 C is a physiological response affected by many others characters than stomatal control and photosynthetic capacity, like leaf area, nitrogen content, phenology, carbon allocation, root characteristics and hydraulic properties.…”

Effects of site preparation with micro-basins on Pinus halepensis Mill. afforestations in a semiarid ombroclimate

“…The main reason for the improvement of growth in microbasins is clearly better availability of water in the soil which can be used up by the plants [9,12,30,33], as, even if in these cases the soil has been removed, which also improves growth, [4,6,29], the volume of growth affected is the same in both cases. In the other hand, when a water constraint is imposed there is less shoot growth [15].…”

“…This is the reason why the introduction of seedlings linked to the site preparation focused on concentrating runoff water on the seedling bed can not only improve the afforestation and avoid its failure [2,9] but also increase the afforestation growth [12,30].…”