Nitrate and phosphate availability and distribution have different effects on root system architecture of Arabidopsis

Abstract

SummaryPlant root systems can respond to nutrient availability and distribution by changing the three-dimensional deployment of their roots: their root system architecture (RSA). We have compared RSA in homogeneous and heterogeneous nitrate and phosphate supply in Arabidopsis. Changes in nitrate and phosphate availability were found to have contrasting effects on primary root length and lateral root density, but similar effects on lateral root length. Relative to shoot dry weight (DW), primary root length decreased with increasing nitrate availability, while it increased with increasing phosphate supply. Lateral root density remained constant across a range of nitrate supplies, but decreased with increasing phosphate supply. In contrast, lateral root elongation was suppressed both by high nitrate and high phosphate supplies. Local supplies of high nitrate or phosphate in a patch also had different effects. Primary root growth was not affected by a high nitrate patch, but growth through a high phosphate patch reduced primary root growth after the root left the patch. A high nitrate patch induced an increase in lateral root density in the patch, whereas lateral root density was unaffected by a high phosphate patch. However, both phosphate-and nitrate-rich patches induced lateral root elongation in the patch and suppressed it outside the patch. This co-ordinated response of lateral roots also occurs in soil-grown plants exposed to a nutrient-rich patch. The auxin-resistant mutants axr1, axr4 and aux1 all showed the wild-type lateral root elongation responses to a nitrate-rich patch, suggesting that auxin is not required for this response.

Plasticity of the Arabidopsis Root System under Nutrient Deficiencies

“…Until now, a detailed examination of the effects of nutrient deficiencies on RSA has been fragmented or totally absent. In fact, only P, N, and, very recently, K deficiency-induced modifications of RSA were more exhaustively assessed in Arabidopsis (Linkohr et al, 2002;Sanchez-Calderon et al, 2005;Kellermeier et al, 2013). In other cases, although the effects of nutrient deficiencies on root development have been reported (for review, see López-Bucio et al, 2003;Nibau et al, 2008), these effects were either restricted to root hair formation (e.g.…”

“…In fact, plants can respond to the heterogenous availability of resources by allocating roots where the most favorable conditions are found (Zhang and Forde, 1998;Linkohr et al, 2002;Remans et al, 2006;Lima et al, 2010;Giehl et al, 2012). When grown under limited phosphorus (P) availability, roots exhibit a shallower architecture that results from the inhibition of PR elongation and the concomitant increase in LR formation (Williamson et al, 2001;López-Bucio et al, 2002;Sanchez-Calderon et al, 2005).…”

“…Such an architectural rearrangement of the root is thought to improve the plant's ability to forage P from the usually P-enriched topsoil horizon (Lynch and Brown, 2001;Rubio et al, 2003;Zhu et al, 2005). In contrast to low P, reduced nitrogen (N) availability stimulates PR and particularly LR elongation but not LR initiation (Linkohr et al, 2002;López-Bucio et al, 2003). However, it is noteworthy that under severe N shortage, LR formation is almost completely absent (Krouk et al, 2010), suggesting that plants require a certain level of N to sustain an active foraging strategy.…”

Nitrate transporters: an overview in legumes

“…Regulation of root system architecture Developmental plasticity enables plants to respond to nutrient availability by changing the architecture of their root system (Zhang and Forde 2000;Linkohr et al 2002). Nitrate is one of the major nutrients known to act as a signal molecule in the regulation of root architecture through the regulation of primary root growth and by influencing the emergence and development of lateral roots (LR) Forde 1998, 2000;Zhang et al 1999;Tian et al 2008;Vidal et al 2010;Celis-Arámburo et al 2011).…”

Ecophysiological and anatomical responses ofVallisneria natansto nitrogen and phosphorus enrichment

“…And roots elongated in nutrient-poor patches significantly (Wang and Yu, 2007). Lateral root of Arabidopsis elongation is suppressed by both high nitrate and high phosphate availability (Linkohr et al, 2002). The Fv/Fm ratio reflects the potential quantum efficiency of PSII and is used as a sensitive indicator of plant photosynthetic performance, with optimal values of approximately 0.83 measured for most plant species (Bjorkman and Demmig, 1987).…”