Anatomical root responses of rice to combined phosphorus and water stress – relations to tolerance and breeding opportunities

Abstract

Drought and low P availability are major limitations for rainfed rice (Oryza spp.) production. Root anatomy plays a key role in resource acquisition and tolerance to P and water limitations. Root anatomical responses of three contrasting rice varieties to combinations of different levels of P (deficient to non-limiting) and water availability (water stress to submergence) were evaluated in two pot trials. P availability was the dominant growth-limiting factor, but anatomical root responses to water availability were more prominent than responses to P availability. Cortical cell file number and number of xylem vessels decreased as a response to water stress, but stele and xylem diameter increased. Low P availability induced thinner xylem vessels and a thinner stele. Drought tolerance related to an overall thicker root stele, thicker xylem vessels and a larger water conductance. Some root traits were observed to be more responsive to water and P availability, whereas other traits were more robust to these environmental factors but highly determined by variety. The observed genotypic variation in root anatomy provides opportunities for trait-based breeding. The plasticity of several traits to multiple environmental factors highlights the need for strategic trait selection or breeding adapted to specific target environments.

Some Mechanisms Modulating the Root Growth of Various Wheat Species under Osmotic-Stress Conditions

“…Tolerance to osmotic stress can also be provided by a thicker root stele, and, respectively, by thicker xylem vessels and greater water conductivity. Stele diameter enlargement, and consequently, the cross-sectional area of stele during water stress contributes to decline in radial path for water flow and higher axial conductivity [38,39]. A clear illustration of this is the ratio of area of radial section of stele to the area of radial section of root [39].…”

Micro‐dose placement of phosphorus induces deep rooting of upland rice

“…NERICA4 is an upland rice variety developed by the Africa Rice Center (AfricaRice) using interspecific crosses between Oryza sativa (Asian rice) and Oryza glaberrima (African rice). NERICA4 is known for its robust performance under droughts, but it is relatively susceptible to low P availability (De Bauw et al, 2019b, 2019aKoide et al, 2013). The root system of the latter variety was previously characterized as having relatively limited number of nodal roots, able to penetrate to deep layers (De Bauw et al 2020).…”

Root system architecture and anatomical traits variability of alfalfa at the seeding stage

“…Larger vessels diameter contributed to higher root axial hydraulic conductance in peach rootstocks (Tombesi et al 2010). The higher stele diameter could enable crops with stronger capacity of root penetration and P uptake to better adapt to drought stress (De Bauw et al 2019). In this study, total stele area and xylem vessel area were both positively correlated with N and P uptake, indicating larger total stele area and xylem vessel area could improve the uptake of N and P by reducing the axial transport resistance in alfalfa.…”

“…After scanning, a 1 cm long root segment was cut at 5 cm from the taproot tip, then preserved in formaldehyde-acetic acid-ethanol xative (75% ethanol, glacial acetic acid, 40% formaldehyde) and stored at 4°C until further analysis (De Bauw et al 2019;Zhou et al 2020). The segments were embedded in para n individually after dehydration by immersion in a sequence of alcohol solutions.…”

“…Root foraging ability is not only in uenced by root morphology, but also closely related to anatomical traits (Lynch 2019). Fewer cortical cell les could reduce radial transport resistance of nutrient in root system and improve water capture by reducing the metabolic costs of soil exploration under drought (De Bauw et al 2019;Lynch 2013). Changes in internal structure of root like increasing cortex to stele ratio made a better balance between nutrient absorption and transportation (Kong et al 2016).…”