Proline-Mediated Drought Tolerance in the Barley (Hordeum vulgare L.) Isogenic Line Is Associated with Lateral Root Growth at the Early Seedling Stage

A vigorous root system in barley promotes water uptake from the soil under water-limited conditions. We investigated three spring barley genotypes with varying water stress responses using rhizoboxes at the seedling stage. The genotypes comprised two elite German cultivars, Barke and Scarlett, and a near-isogenic line, NIL 143. The isogenic line harbors the wild allele pyrroline-5-carboxylate synthase1-P5cs1. Root growth in rhizoboxes under reduced water availability conditions caused a significant reduction in total root length, rooting depth, root maximum width, and root length density. On average, root growth was reduced by more than 20% due to water stress. Differences in organ proline concentrations were observed for all genotypes, with shoots grown under water stress exhibiting at least a 30% higher concentration than the roots. Drought induced higher leaf and root proline concentrations in NIL 143 compared with any of the other genotypes. Under reduced water availability conditions, NIL 143 showed less severe symptoms of drought, higher lateral root length, rooting depth, maximum root width, root length density, and convex hull area compared with Barke and Scarlett. Within the same comparison, under water stress, NIL 143 had a higher proportion of lateral roots (+30%), which were also placed at deeper substrate horizons. NIL 143 had a less negative plant water potential and higher relative leaf water content and stomatal conductance compared with the other genotypes under water stress. Under these conditions, this genotype also maintained an enhanced net photosynthetic rate and exhibited considerable fine root growth (diameter class 0.05–0.35 mm). These results show that water stress induces increased shoot and root proline accumulation in the NIL 143 barley genotype at the seedling stage and that this effect is associated with increased lateral root growth.

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Associations Between Productivity, Root Growth and Carbon Isotope Discrimination in Phaseolus vulgaris Under Water Deficit

Functional Plant Biology ◽

10.1071/pp9900189 ◽

1990 ◽

Vol 17 (2) ◽

pp. 189 ◽

Cited By ~ 49

Author(s):

JW White ◽

JA Castillo ◽

J Ehleringer

Keyword(s):

Phaseolus Vulgaris ◽

Gas Exchange ◽

Root Growth ◽

Water Deficit ◽

Root Length ◽

Root Length Density ◽

Crop Growth ◽

Cultivar Differences ◽

Rooting Depth ◽

Rainfed Conditions

Recent theoretical and empirical studies have indicated that isotopic discrimination against 13C (Δ) during photosynthesis in C3 plants reflects variation in intercellular CO2 concentration (ci). Under water deficit, cultivar differences in Δ may indicate differences in leaf gas exchange characteristics. Cultivar differences in Δ may also result indirectly from genetic variation in root characteristics affecting the level of water stress experienced by the canopy. Differences in root growth affecting the degree of dehydration postponement could prolong gas exchange activity and the maintenance of relatively high ci and Δ. To evaluate relations between root growth, productivity and Δ in common bean (Phaseolus vulgaris L.), Δ and crop growth parameters, including biomass production, grain yield and root length density, were determined for ten bean genotypes grown under rainfed conditions at two sites in Colombia which differed primarily in soil fertility and effective rooting depth. The 10 genotypes were also grown under irrigation at the more fertile site. Under rainfed conditions, root length density was positively correlated with Δ in the fertile Mollisol at Palmira, and was also positively correlated with Δ in the infertile Oxisol at Quilichao if one possibly abberent genotype was excluded. At Palmira, reduced crop growth and seed yield were associated with low Δ values. At Quilichao, intermediate Δ values were associated with the greatest growth and yield. Under irrigation at Palmira there was no association between growth or yield and Δ.

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Association between root growth angle and root length density of a near-isogenic line of IR64 rice with DEEPER ROOTING 1 under different levels of soil compaction

Plant Production Science ◽

10.1080/1343943x.2017.1288550 ◽

2017 ◽

Vol 20 (2) ◽

pp. 162-175 ◽

Cited By ~ 7

Author(s):

Poornima Ramalingam ◽

Akihiko Kamoshita ◽

Vivek Deshmukh ◽

Sousuke Yaginuma ◽

Yusaku Uga

Keyword(s):

Root Growth ◽

Root Length ◽

Soil Compaction ◽

Root Length Density ◽

Isogenic Line ◽

Near Isogenic Line ◽

Growth Angle ◽

Root Growth Angle ◽

Different Levels

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Effect of defoliation by grazing or shoot removal on the root growth of field-grown wheat (Triticum aestivum L.)

Crop and Pasture Science ◽

10.1071/cp14241 ◽

2015 ◽

Vol 66 (4) ◽

pp. 249 ◽

Cited By ~ 15

Author(s):

J. A. Kirkegaard ◽

J. M. Lilley ◽

J. R. Hunt ◽

S. J. Sprague ◽

N. K. Ytting ◽

...

Keyword(s):

Root Growth ◽

Grain Yield ◽

Root Length ◽

Root Length Density ◽

Yield Potential ◽

Rooting Depth ◽

Wheat Crop ◽

Root Depth ◽

Surface Layers ◽

Shoot Removal

Dual-purpose crops for grazing and grain production can be highly profitable, provided grazing does not cause significant loss of grain yield. In many plants, defoliation causes a transient reduction in the allocation of resources to stem and root growth and remobilisation of soluble resources to re-establish leaf area rapidly. In Australia, the usual autumn and winter period of defoliation for grazed crops, May–July, coincides with a phase of near-linear root depth penetration in ungrazed crops, and the crop recovery period after grazing occurs during stem elongation, when grain number and yield potential are determined. However, few studies have investigated the potential impact of crop defoliation through grazing on root growth of wheat in the field. We investigated the effect of defoliation by grazing or shoot removal on the root growth of wheat crops in four field experiments in south-eastern Australia in which the timing, frequency and intensity of defoliation varied. Despite significant impacts of defoliation on aboveground biomass (50–90% reduction) and grain yield (10–43% reduction) in all experiments, we found little evidence of effects on the rate of root penetration or final rooting depth. A notable exception was observed in one experiment when defoliation commenced very early (four-leaf stage, Zadoks growth stage Z14) in a repeatedly defoliated crop, reducing rooting depth from 1.65 to 1.35 m. The only other measured impact on roots was in an early-sown winter wheat crop grazed by sheep for 3 months (6 June–3 September), in which root length density was reduced by ~50% in surface layers above 1.0 m depth, but there was no impact on maximum root depth or root length density at 1.0–2.0 m depth. Our results suggest that grazing has little impact on the rooting depth of wheat unless it occurs very early and repeatedly, when plants are allocating significant resources to establish the primary roots. However, there may be some reduction in the density of roots in surface layers during recovery after long-term grazing, presumably associated with reduced proliferation of the nodal root system. We conclude that most significant yield penalties due to grazing relate to impacts on the assimilation of aboveground resources, rather than to reduced water or nutrient acquisition by roots.

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Effect of variety, irrigation regime and planting date on depth, rate, duration and density of root growth in the potato (Solanum tuberosum) crop

The Journal of Agricultural Science ◽

10.1017/s0021859601001332 ◽

2001 ◽

Vol 137 (3) ◽

pp. 251-270 ◽

Cited By ~ 48

Author(s):

M. A. STALHAM ◽

E. J. ALLEN

Keyword(s):

Root Growth ◽

Root Length ◽

Root Length Density ◽

Rooting Depth ◽

Major Influence ◽

Soil Conditions ◽

Root Penetration ◽

Irrigation Regime ◽

Root Extension ◽

Short Period

Experiments were conducted over the period 1987–94 at Cambridge University Farm and two other sites to examine the effect of various husbandry factors, particularly variety and irrigation regime, on rate, depth and density of rooting in potatoes. Maximum rooting depth ranged from 59 to 140 cm, indicating that potatoes can root to considerable depths and thereby have access to large volumes of water to satisfy the potential demand for water created by the atmospheric conditions and the size of the canopy. Root extension vertically through the soil profile was best described as a three-phase process: an initial rapid period lasting 3–5 weeks with growth rates c. 1·2 cm/day, a second period of slower growth (c. 0·8 cm/day), followed by cessation of root extension for the rest of the life of the crop. Variety had a major influence on the ultimate depth of rooting, primarily owing to variations in the length of the different periods of rooting rather than the rate in each period. It was observed that changes in the rate, or the cessation of root penetration were always preceded 4–9 days earlier by a change in the rate, or cessation, of leaf appearance. This feature should make it possible to characterize the duration of rooting of varieties through measurement of leaf emergence. Varieties which ceased leaf production early, such as Atlantic, were found to have a duration of root growth of c. 60 days, with Cara rooting for c. 30 days longer. Maximal total root length (TRL) and root length density (RLD) in the experiments reported were 16·9 km/m2 and 5·5 cm/cm3, respectively, similar to those found previously in potatoes and crops such as sugar beet, but considerably greater than many other vegetables. Rooting density decreased with depth, but the root systems were not as surface-oriented as many other studies have shown. When TRL was close to its maximum, the vertical distribution of RLD showed that between 40 and 73% was confined to the upper 30 cm, with irrigated crops possessing a greater proportion of their roots in the plough layer. Despite being planted in rows 70–91 cm apart, rooting systems were homogeneously distributed in a horizontal direction by c. 35 days after emergence, at which time the roots had reached a depth of c. 50 cm. Therefore, apart from a short period after emergence, the potato crop is capable of accessing considerable volumes of soil from which to extract water and nutrients. Ensuring that soil conditions are conducive to maximal rates of root growth should be the target for growers, since this will lead to a more efficient use of soil water and irrigation.

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Root length density and water uptake in cereals and grain legumes: how well are they correlated

Australian Journal of Agricultural Research ◽

10.1071/ar9870513 ◽

1987 ◽

Vol 38 (3) ◽

pp. 513 ◽

Cited By ~ 149

Author(s):

AP Hamblin ◽

D Tennant

Keyword(s):

Water Uptake ◽

Root Length ◽

Root Zone ◽

Root Length Density ◽

Genotypic Variation ◽

Root Water Uptake ◽

Grain Legumes ◽

Rooting Depth ◽

Rates Of Change ◽

Axial Resistance

Total root length per unit ground area (La) is often considered to be directly related to the amount and rate of water uptake. Experiments were conducted to compare the water use of spring wheat, barley, lupin (L. angustifolius) and field pea on four differing soil types in drought-stressed conditions. The La values of cereals were consistently five to ten times as large as those of grain legumes, whereas the aboveground biomass was sim~iar and never greater than twice that of the grain legumes. Growing-season water loss (WL) from the soil profile was very similar for wheat and lupins, despite this big difference in root length. Soil evaporation may have been greater under lupins, but when crop water uptake was compared for the period when leaf area was greatest, rates of change in soil water content within the root zone were still similar and were not well correlated with La. Specific root water uptake (Ur) was consistently greater for lupin than wheat. Maximum rooting depth was better correlated with WL than was La in all cases. Higher Ur values in lupin and pea may be related to their large and abundant metaxylem vessels, which give much lower axial resistance than in cereals. These results provide strong evidence for genotypic variation in root morphology, density and root extension between dicotyledenous and monocotyledenous species. They also indicate that La is not necessarily the root morphological characteristic most responsible for efficiency of water uptake in drought-stressed environments.

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An evaluation of the minirhizotron technique for estimating root distribution in potatoes

The Journal of Agricultural Science ◽

10.1017/s0021859600078151 ◽

1991 ◽

Vol 116 (3) ◽

pp. 341-350 ◽

Cited By ~ 27

Author(s):

C. J. Parker ◽

M. K. V. Carr ◽

N. J. Jarvis ◽

B. O. Puplampu ◽

V. H. Lee

Keyword(s):

Root Growth ◽

Root Length ◽

Root Length Density ◽

Quantitative Measure ◽

Total Root Length ◽

Root Tips ◽

Core Sampling ◽

Glass Tubes ◽

Poor Soil ◽

Made In

SUMMARYThe minirhizotron technique was evaluated for estimating root length density in potatoes (Solanum tuberosum‘Record’) by comparing observations in angled 45° glass tubes with corresponding root length densities obtained by (a) destructive core sampling, and from (b) counts of root tips on the soil face of excavated trenches. Measurements were made in a field experiment in Bedfordshire, UK, in 1985, with shallow and deep cultivation as variables, and in a glasshouse trial.Only at depths below 0·3 m did root lengths observed with minirhizotrons reflect at all closely those estimated from core sampling and even then there was a tendency to overestimate root density. In the surface cultivated layers, where 80–90% of the total root length was present, results from minirhizotrons were unreliable, probably because of poor soil–tube contact and, in soils which shrink on drying, preferential root growth at the interface between the soil and the glass.Minirhizotrons can provide a realistic estimate of the rate of root growth of potatoes with depth over time when compared with maximum depths of water extraction, but appear to be unreliable for providing a quantitative measure of total root length density.

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ROOT GROWTH OF CHINESE JUNIPER DURING THE FIRST THREE YEARS AFTER PLANTING

HortScience ◽

10.21273/hortsci.25.9.1064e ◽

1990 ◽

Vol 25 (9) ◽

pp. 1064e-1064 ◽

Cited By ~ 1

Author(s):

Edward F. Gilman ◽

Michael E. Kane

Keyword(s):

Root Growth ◽

Root System ◽

Root Length ◽

Root Length Density ◽

Root Diameter ◽

Root Weight ◽

Root Area ◽

Black Plastic ◽

Shoot Weight ◽

Root Spread

Shoot and root growth were measured on Chinese juniper (Juniperus chinensis L.) Var. `Torulosa', `Sylvestris', `Pfitzeriana' and `Hetzii' 1, 2 and 3 years after planting into a simulated landscape from 10-liter black plastic containers. Mean diameter of the root system increased quadratically averaging 1, 2 m/year; whereas, mean branch spread increased at 0, 33 m/year, Three years after planting, root spread was 2, 75 times branch spread and roots covered an area 5.5 times that covered by the branches. Percentage of total root length located within the dripline of the plants remained fairly constant (71-77%) during the first 3 years following planting. Root length density per unit area increased over time but decreased with distance from the trunk. In the first 2 years after planting shoot weight increased faster than root `weight. However, during the third year after planting, the root system increased in mass and size at a faster rate than the shoots. Root length was correlated with root weight within root-diameter classes, Root spread and root area were correlated with trunk area, branch spread and crown area.

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Effects of tillage on soil physical properties and root growth of maize in loam and clay in central China

Plant Soil and Environment ◽

10.17221/57/2013-pse ◽

2013 ◽

Vol 59 (No. 7) ◽

pp. 295-302 ◽

Cited By ~ 17

Author(s):

B. Ji ◽

Y. Zhao ◽

X. Mu ◽

K. Liu ◽

C. Li

Keyword(s):

Root Growth ◽

Water Content ◽

Bulk Density ◽

Root Length ◽

Root Length Density ◽

Penetration Resistance ◽

Soil Bulk Density ◽

Conventional Tillage ◽

Central China ◽

Deep Tillage

Subsoil compaction can result in unfavourable soil physical conditions and hinder the root growth of maize. The effects of deep tillage and conventional tillage on soil physical properties and root growth of maize were studied during 2010–2011 at two sites (loam at Hebi and clay at Luohe) in central China. The results showed that soil penetration resistance, bulk density, water content and root length density were significantly affected by tillage, soil depth and year. Deep tillage had lower penetration resistance and lower soil bulk density, but higher soil water content than conventional tillage across years and depths. Averaged over the whole soil profile, deep tillage not only significantly decreased penetration resistance and soil bulk density, but significantly increased soil water content and root length density on loam, while deep tillage only significantly increased the root length density on clay. We conclude that deep tillage on the loam is more suitable for the root growth of summer maize.

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