Genetic Variability in Phosphorus Acquisition and Utilization Efficiency from Sparingly Soluble P‐Sources by Brassica Cultivars under P‐Stress Environment

Abstract

Plants display an array of classical strategies to maximize phosphate (Pi) acquisition from sparingly soluble P sources. Acclimation to Pi-stress via elegant Pi-starvation induced (PSI) adjustments would reduce our current overreliance on expensive, polluting and non-renewable Pi-fertilizers. Nevertheless, differences in the ability of various species to solubilize sparingly soluble P-sources have been often evidenced; inter-cultivar variations are scarcely documented. Brassica is known as an effective, non-mycorrhizal user of sparingly soluble P-sources. Various growth parameters and biomass accumulation by genetically diverse Brassica cultivars were determined in four experiments using hydroponics and quartz sand culture media. Role of PSI root mediated pH changes, organic anions (OAs) exudation and altered root architecture in mobilization and acquisition of sparingly soluble P-forms [Jordan rock-P (RP) at 2 g l )1 and Ca 3 (PO 4 ) 2 (TCP) at 0.2 g l )1 respectively] was investigated. Cultivars showed considerable genetic variations in biomass accumulation, various growth parameters and root-shoot ratio. Concentration and total uptake of P, specific absorption rate of P, P-transport rate and P-utilization efficiency (PUE) were also significantly (P < 0.001) different for various cultivars and their dry matter was significantly correlated with P-uptake [r = 0.94** (significant at 1% level)]. P-tolerant cultivars showed substantial decrease in solution media pH because of H + efflux and exuded more carboxylates than low P-sensitive cultivars under P-starvation. P-uptake by cultivars increased linearly with decreasing pH. The amount and types of OAs exuded from the roots of P-starved plants differed from those of plants grown under P-sufficient environment. In split pot study, with TCP and RP supplied spatially separated from other nutrients, efficient cultivars were still able to mobilize RP and TCP more efficiently than inefficient cultivars. In rhizobox study, the elongation rates of primary roots decreased but the elongation rates of the branched zones of primary roots and the length of lateral roots increased under P-starvation. Tested cultivars showed genetic diversity in accessing, mobilization, acquisition and utilization of Pi from sparingly soluble P forms. An arrange marriage of plant traits can explain cultivar's access to different forms of sparingly soluble P, and in addition to altered lateral root topology and enhanced P-uptake and PUE, enhanced H + efflux and OAs exudation are key factors in Pi scavenging from extra cellular sparingly soluble P-forms.

The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

“…1). Akhtar et al (2008) demonstrated a superior root growth under P starvation (LP) in Brassica, which helps to acquire more P. It was also observed that wheat genotypes with larger root dry weight at LP level had relatively lower reductions in shoot dry matter (Yaseen and Malhi 2011). In agreement with these results, we supposed that higher growth and .…”

“…Thus, it may be suggested that XZ99 has the ability to develop new roots for greater exploration for P during P starvation. Similarly, it has also been confirmed that in Brassica species, root systems with higher ratios of surface area to volume could more effectively explore for nutrients in the soil (Akhtar et al 2008).…”

“…Moreover, the shoot/root P concentration ratio, which describes the partitioning of P between shoots and roots, was higher in XZ99 and ZD9 under LP. It was also reported that the efficient Brassica cultivar had a significant correlation between phosphate transport rate (PTR) and shoot P concentration and uptake (Akhtar et al 2008). The cultivar with higher PTR was able to retain higher P in their shoots under P starvation.…”

Management of soil phosphorus and plant adaptation mechanisms to phosphorus stress for sustainable crop production: a review

“…However, plants may still differ in tolerance of P stress effect on leave growth mainly due to difference in the ability to maintain cell division (Chiera et al, 2002;Assuero et al, 2004), leaf epidermal cell expansion (Radin and Eidenbock, 1984) or both (Kavanova et al, 2006), under lower tissue P concentration. Alternatively, plants may also retranslocate limited P from older leaves to younger leaves to maintain Pi at levels that permit optimal physiological activities including cell division (Plaxton and Carswell, 1999;Akhtar et al, 2008).…”

Genotypic variation in phosphorus acquisition from sparingly soluble P sources is related to root morphology and root exudates in Brassica napus

“…Root morphology is a key factor related to P acquisition in plants. The contribution of root morphology to P uptake has been reported for many plant species [8,9]. Rhizosphere acidification may play an important role in mobilizing phosphate from calcium phosphates [10].…”