Clone-Specific Response in Leaf Nitrate Reductase Activity among Unrelated Hybrid Poplars in relation to Soil Nitrate Availability

Abstract

In this field study, we used in vivo NRA activity in hybrid poplar leaves as an indicator of NO 3 − assimilation for five unrelated hybrid poplar clones. We also examined if leaf NRA of these clones is influenced to the same extent by different levels of soil NO 3 − availability in two riparian agroforestry systems located in pastures. Leaf NRA differences of more than one order of magnitude were observed between the clones, clearly showing their different abilities to reduce NO 3 − in leaves. Clone DxN-3570, a P. deltoides x P. nigra hybrid (Aigeiros intrasectional hybrid), always had the highest leaf NRA during the field assays. This clone was also the only one to increase its leaf NRA with increasing NO 3 − soil availability, which resulted in a significant Site x Clone interaction and a positive relationship between soil NO 3 − concentration and NRA. All of the four other clones studied had one or both parental species from the Tacamahaca section. They had relatively low leaf NRA and they did not increase their leaf NRA when grown on the NO 3 − rich site. These results provide evidence that NO 3 − assimilation in leaves varies widely among hybrid poplars of different parentages, suggesting potential preferences for N forms.

Plastic Allometry in Coarse Root Biomass of Mature Hybrid Poplar Plantations

“…The PRS-probes consist of an ion exchange membrane encapsulated in a thin plastic probe, which is inserted into the ground with little disturbance of soil structure. Nutrient availability predicted with this method is generally significantly correlated with conventional soil extraction methods over a wide range of soil types [53], and which has also been corroborated in poplar riparian agroforestry systems of the study region [54,55]. In August 2012, four pairs of probes (an anion and a cation probe in each pair) were buried in the A horizon of each plot for a 35-day period.…”

Root biomass and soil carbon distribution in hybrid poplar riparian buffers, herbaceous riparian buffers and natural riparian woodlots on farmland

“…No site preparation was done prior to planting and tending operations consisted in a single localised herbicide treatment (1 m 2 /tree) in June 2003. Information regarding hybrid poplar buffer management, aboveground biomass and volume growth, aboveground nutrient and C accumulation, and understory biomass and diversity can be found in previous studies (Fortier et al 2010a , 2010b , 2011 ; 2012 ; 2013 ).…”

Biomass and Volume Yield in Mature Hybrid Poplar Plantations on Temperate Abandoned Farmland

“…In a previous field experiment involving the same poplar genotypes, clone DxN-3570 had the greatest leaf nitrate reductase activity (NRA), and was the only clone that showed an increase in NRA in response to a soil increase in nitrate (NO3) availability [56]. This evidence suggested that this clone has a greater ability for NO3 assimilation in its leaves than the other clones, potentially reflecting its preference for soil NO3 over NH4, as also observed for P. deltoides [18,57].…”