We compared photosynthesis-nitrogen relationships of one broad-leaved (Populus x euroamericana) and one conifer (Pseudotsuga menziesii). Plants were grown in large pots, as to allow free root development, and were kept well watered. Three nitrogen treatments were defined: low, intermediate and high nitrogen supply. The following parameters were measured/estimated: light-saturated photosynthesis (Amax), leaf mass per area (LMA), leaf nitrogen and chlorophyll concentration, maximum carboxylation (Vcmax) and electron transport rate (Jmax), nitrogen partitioning among active Rubisco (PR), bioenergetic pools (PB) and light-harvesting complex (PLH). Nitrogen supply affected significantly leaf nitrogen content on an area basis. LMA did not differ between species and was not affected by treatments. A positive correlation was found between chlorophyll and leaf nitrogen content, and between leaf nitrogen and photosynthetic parameters, Amax, Jmax and Vcmax. Poplar showed Amax and Vcmax higher than douglas-fir. Slopes of Amax-nitrogen and Vcmax-nitrogen relationships were significantly higher in poplar. Amax, Jmax and Vcmax were not significantly correlated with LMA. The ratio between Jmax and Vcmax was significantly higher in douglas-fir. Photosynthetic nitrogen use efficiency was negatively correlated with leaf nitrogen content in douglas-fir but not in poplar. Proportions of leaf nitrogen in light-harvesting (PLH), bioenergetic pools (PB) and Rubisco (PR) were negatively correlated to leaf nitrogen content in douglas-fir, whereas in poplar a negative correlation was found only for PLH. PR was significantly higher in poplar than in douglas-fir. Overall, our data suggest that differences between douglas-fir and poplar in photosynthesis-nitrogen relationship and PNUE primarily reflects a different investment of nitrogen to photosynthetic apparatus, in particular to Rubisco, independently on leaf structure.
Photosynthesis-nitrogen relationship: interpretation of different patterns between Pseudotsuga menziesii and populus x euroamericana in a ?mini-stand? experiment
2003
Abstract
We compared photosynthesis-nitrogen relationships of one broad-leaved (Populus x euroamericana) and one conifer (Pseudotsuga menziesii). Plants were grown in large pots, as to allow free root development, and were kept well watered. Three nitrogen treatments were defined: low, intermediate and high nitrogen supply. The following parameters were measured/estimated: light-saturated photosynthesis (Amax), leaf mass per area (LMA), leaf nitrogen and chlorophyll concentration, maximum carboxylation (Vcmax) and electron transport rate (Jmax), nitrogen partitioning among active Rubisco (PR), bioenergetic pools (PB) and light-harvesting complex (PLH). Nitrogen supply affected significantly leaf nitrogen content on an area basis. LMA did not differ between species and was not affected by treatments. A positive correlation was found between chlorophyll and leaf nitrogen content, and between leaf nitrogen and photosynthetic parameters, Amax, Jmax and Vcmax. Poplar showed Amax and Vcmax higher than douglas-fir. Slopes of Amax-nitrogen and Vcmax-nitrogen relationships were significantly higher in poplar. Amax, Jmax and Vcmax were not significantly correlated with LMA. The ratio between Jmax and Vcmax was significantly higher in douglas-fir. Photosynthetic nitrogen use efficiency was negatively correlated with leaf nitrogen content in douglas-fir but not in poplar. Proportions of leaf nitrogen in light-harvesting (PLH), bioenergetic pools (PB) and Rubisco (PR) were negatively correlated to leaf nitrogen content in douglas-fir, whereas in poplar a negative correlation was found only for PLH. PR was significantly higher in poplar than in douglas-fir. Overall, our data suggest that differences between douglas-fir and poplar in photosynthesis-nitrogen relationship and PNUE primarily reflects a different investment of nitrogen to photosynthetic apparatus, in particular to Rubisco, independently on leaf structure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
