Leaf and root attributes as growth and phosphorus uptake determinants in two grass species from South America’s natural grasslands

Abstract

Phosphorus uptake by grass species from natural South American grasslands can change depending on root and leaf attributes capable of determining higher, or lower, relative growth rate. The aim of the current study is to investigate whether leaf and root attributes capable of determining leaf and root area production in native C4 grass species Axonopus affinis and Andropogon lateralis are related to higher relative growth rate (RGR), P uptake capacity (maximum P influx; Imax) and concentration. Species grown in 2-litre pots with added nutrition solution were subjected to two treatments, namely 5 μM P l−1 and 30 μM P l−1. Solution aliquots (10 ml) were collected for 30 hours at the end of the study to determine P concentrations. RGR was 3.6 and 2.8 times higher in A. affinis than in A. lateralis in treatments with 5 μM P and 30 μM P. Axonopus affinis recorded the highest P concentration in leaf tissue. This outcome was associated with Imax 85% higher in A. affinis. High RGR was associated with larger leaf and root surface area per dry mass unit, as well as with high P influx capacity and with higher affinity transporters. These species often prevail in areas accounting for greater natural fertility and are more responsive to phosphate fertilization.

Phosphate sources affect P and N nutrition in pluri-specific natural grasslands in the Brazilian Pampa biome

“…The patterns regarding the uptake and use of P by forage species in this study corroborated the grouping patterns observed by Marques et al (2020a, b). They found that some forage species of the Pampa are functionally grouped as specialists in acquiring soil P and accumulating more P in their tissues; whereas other plants are specialists in using more efficiently the P absorbed and produce more biomass per unity of P. By studying the mechanisms behind these patterns, Marques et al (2021) found that forage species from the South American native grasslands with more efficient P uptake strategies also have larger root area and length per unit of root dry matter. These forage species have a higher potential to increase growth by applying P fertilizers.…”

“…These forage species have a higher potential to increase growth by applying P fertilizers. On the other hand, species that have more conservative strategies have thicker and denser roots (smaller root area and length per unity of root dry matter), and thus, they have a lower capacity to absorb P and to respond to increased P availability in the soil after fertilization (Marques et al, 2021).…”