Genetic variation for adventitious rooting in response to low phosphorus availability: potential utility for phosphorusacquisition from stratified soils

We hypothesized that adventitious roots may improve crop adaptation to low-phosphorus soils by enhancing topsoil foraging. In a tropical field study, phosphorus stress stimulated adventitious rooting in two phosphorus-efficient genotypes of common bean (Phaseolus vulgaris L.) but not in two phosphorus-inefficient genotypes. Although phosphorus availability had no consistent effects on the length or biomass of whole root systems, it had differential effects on adventitious, basal, and taproots within root systems in a genotype-dependent manner, resulting in increased allocation to adventitious roots in efficient genotypes. Adventitious roots had greater length per unit biomass than other root types, especially under phosphorus stress. Adventitious roots had less construction cost than basal roots, despite having similar tissue nitrogen content. Phosphorus stress reduced lateral root density, and adventitious roots had less lateral root density than basal roots. Lateral roots formed further from the root tip in adventitious roots compared with basal roots, especially under phosphorus stress. Field results were confirmed in controlled environments in solid and liquid media. Stimulation of adventitious rooting by phosphorus stress tended to be greater in wild genotypes than in cultivated genotypes. We propose that adventitious rooting is a useful adaptation to low phosphorus availability, because adventitious roots explore topsoil horizons more efficiently than other root types.

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The contribution of lateral rooting to phosphorus acquisition efficiency in maize (Zea mays) seedlings

Functional Plant Biology ◽

10.1071/fp04046 ◽

2004 ◽

Vol 31 (10) ◽

pp. 949 ◽

Cited By ~ 136

Author(s):

Jinming Zhu ◽

Jonathan P. Lynch

Keyword(s):

Growth Rate ◽

Lateral Root ◽

Root Respiration ◽

Lateral Roots ◽

Biomass Accumulation ◽

Phosphorus Availability ◽

Phosphorus Acquisition ◽

Relative Growth ◽

Phosphorus Stress ◽

Low Phosphorus

Low soil phosphorus availability is a primary constraint for plant growth in many terrestrial ecosystems. Lateral root initiation and elongation may play an important role in the uptake of immobile nutrients, such as phosphorus, by increasing soil exploration and phosphorus solubilisation. The overall objective of this study was to assess the value of lateral rooting for phosphorus acquisition through assessment of the ‘benefit’ of lateral rooting for phosphorus uptake and the ‘cost’ of lateral roots in terms of root respiration and phosphorus investment at low and high phosphorus availability. Five recombinant inbred lines (RILs) of maize derived from a cross between B73 and Mo17 with contrasting lateral rooting were grown in sand culture in a controlled environment. Genotypes with enhanced or sustained lateral rooting at low phosphorus availability had greater phosphorus acquisition, biomass accumulation, and relative growth rate (RGR) than genotypes with reduced lateral rooting at low phosphorus availability. The association of lateral root development and plant biomass accumulation under phosphorus stress was not caused by allometry. Genotypes varied in the phosphorus investment required for lateral root elongation, owing to genetic differences in specific root length (SRL, which was correlated with root diameter) and phosphorus concentration of lateral roots. Lateral root extension required less biomass and phosphorus investment than the extension of other root types. Relative growth rate was negatively correlated with specific root respiration, supporting the hypothesis that root carbon costs are an important aspect of adaptation to low phosphorus availability. Two distinct cost–benefit analyses, one with phosphorus acquisition rate as a benefit and root respiration as a cost, the other with plant phosphorus accumulation as a benefit and phosphorus allocation to lateral roots as a cost, both showed that lateral rooting was advantageous under conditions of low phosphorus availability. Our data suggest that enhanced lateral rooting under phosphorus stress may be harnessed as a useful trait for the selection and breeding of more phosphorus-efficient maize genotypes.

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Clonal Variation in Lateral and Basal Rooting of Populus Irrigated with Landfill Leachate

Silvae Genetica ◽

10.1515/sg-2011-0005 ◽

2011 ◽

Vol 60 (1-6) ◽

pp. 35-44 ◽

Cited By ~ 3

Author(s):

R. S. Zalesny ◽

J. A. Zalesny

Keyword(s):

Growth Rate ◽

Root Growth ◽

Landfill Leachate ◽

Clonal Selection ◽

Lateral Roots ◽

Adventitious Rooting ◽

Clonal Variation ◽

Basal Roots ◽

Root Growth Rate ◽

Root Types

AbstractSuccessful establishment and productivity ofPopulusdepends upon adventitious rooting from: 1)lateral rootsthat develop from either preformed or induced primordia and 2)basal rootsthat differentiate from callus at the base of the cutting in response to wounding. Information is needed for phytotechnologies about the degree to whichPopulusadventitious rooting is controlled by effects of individual genotypes, waste waters used as alternative fertigation sources, and their interactions. Our objective was to irrigate twelvePopulusclones with well water (control) or municipal solid waste landfill leachate and to test for differences between initiation of lateral versus basal roots, as well as root growth rate and distributional trends for both root types. We evaluated number and length of lateral roots initiated from upper, middle, and lower thirds of the cutting, as well as basal callus roots. Overall, leachate irrigation affected lateral roots but not basal roots, and there was broad clonal variation between and within root types. On average, there were 129% more lateral than basal roots, which ranged from 3 to 27 (lateral) and 2 to 10 roots (basal). The percent advantage of number of roots from the middle portion of the cutting relative to other sections was 120% (upper), 193% (lower), and 24% (basal). Clones, treatments, and their interaction did not affect root growth rate, which ranged from 1.5 ± 0.6 to 3.4 ± 0.3 cm d−1, with a mean of 2.3 ± 0.2 cm d−1. These results contribute baseline information for clonal selection needed to establishPopulusfor phytotechnologies, energy, and fiber.

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Ethylene modulates genetic, positional, and nutritional regulation of root plagiogravitropism

Functional Plant Biology ◽

10.1071/fp06209 ◽

2007 ◽

Vol 34 (1) ◽

pp. 41 ◽

Cited By ~ 24

Author(s):

Paramita Basu ◽

Yuan-Ji Zhang ◽

Jonathan P. Lynch ◽

Kathleen M. Brown

Keyword(s):

Stress Responses ◽

Phosphorus Availability ◽

Nutritional Regulation ◽

Average Growth ◽

Ethylene Sensitivity ◽

Growth Angle ◽

Rooting Zone ◽

Low Phosphorus ◽

Basal Roots ◽

The Difference

Plagiogravitropic growth of roots strongly affects root architecture and topsoil exploration, which are important for the acquisition of water and nutrients. Here we show that basal roots of Phaseolus vulgaris L. develop from 2–3 definable whorls at the root–shoot interface and exhibit position-dependent plagiogravitropic growth. The whorl closest to the shoot produces the shallowest roots, and lower whorls produce deeper roots. Genotypes vary in both the average growth angles of roots within whorls and the range of growth angles, i.e. the difference between the shallowest and deepest basal roots within a root system. Since ethylene has been implicated in both gravitropic and edaphic stress responses, we studied the role of ethylene and its interaction with phosphorus availability in regulating growth angles of genotypes with shallow or deep basal roots. There was a weak correlation between growth angle and ethylene production in the basal rooting zone, but ethylene sensitivity was strongly correlated with growth angle. Basal roots emerging from the uppermost whorl were more responsive to ethylene treatment than the lower-most whorl, displaying shallower angles and inhibition of growth. Ethylene sensitivity is greater for shallow than for deep genotypes and for plants grown with low phosphorus compared with those supplied with high phosphorus. Ethylene exposure increased the range of angles, although deep genotypes grown in low phosphorus were less affected. Our results identify basal root whorl number as a novel architectural trait, and show that ethylene mediates regulation of growth angle by position of origin, genotype and phosphorus availability.

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What Makes Adventitious Roots?

Plants ◽

10.3390/plants8070240 ◽

2019 ◽

Vol 8 (7) ◽

pp. 240 ◽

Cited By ~ 6

Author(s):

Gonin ◽

Bergougnoux ◽

Nguyen ◽

Gantet ◽

Champion

Keyword(s):

Root System ◽

Adventitious Root ◽

Adventitious Roots ◽

Root Formation ◽

Primary Root ◽

Adventitious Rooting ◽

Adventitious Root Formation ◽

Terrestrial Environment ◽

Root Types ◽

Embryonic Root

The spermatophyte root system is composed of a primary root that develops from an embryonically formed root meristem, and of different post-embryonic root types: lateral and adventitious roots. Adventitious roots, arising from the stem of the plants, are the main component of the mature root system of many plants. Their development can also be induced in response to adverse environmental conditions or stresses. Here, in this review, we report on the morphological and functional diversity of adventitious roots and their origin. The hormonal and molecular regulation of the constitutive and inducible adventitious root initiation and development is discussed. Recent data confirmed the crucial role of the auxin/cytokinin balance in adventitious rooting. Nevertheless, other hormones must be considered. At the genetic level, adventitious root formation integrates the transduction of external signals, as well as a core auxin-regulated developmental pathway that is shared with lateral root formation. The knowledge acquired from adventitious root development opens new perspectives to improve micropropagation by cutting in recalcitrant species, root system architecture of crops such as cereals, and to understand how plants adapted during evolution to the terrestrial environment by producing different post-embryonic root types.

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