In 1999, `Sweet Banana' pepper [Capsicum annuum L. (Grossum Group)] plants were grown under clean cultivation or with red, silver, or black polyethylene selective reflecting (SMR) mulches over the soil surface. Plants in each of three replications per treatment were field-set on 15 June. On 22 Sept., the plants were excavated and their root systems examined using a trench profile method and a succession of trench wall slices. The total numbers of roots of each plant at depths of 5, 10, 15, 20, and 25 cm and 10, 20, 30, 40, 50, and 60 cm from the plant stem were recorded. Distribution and architecture of the root systems were also examined. Plants grown under clean cultivation developed 50 to 60 adventitious roots each, while those grown under red mulch developed ≈20 and those under black and silver mulch about nine adventitious roots each. In all treatments, the adventitious roots radiated downward from the stem at an angle of 35° from the horizontal. No plants had vertical roots. Root system architecture was similar among treatments, with 40% of the roots in the upper 5 cm of soil and 70% in the upper 10 cm. Thirty percent of the roots were within 10 cm, 50% within 20 cm, and nearly 100% within 40 cm of the stem. Root numbers decreased with increasing depth and distance from the stem. The greatest number of lateral roots were produced under silver mulch, intermediate numbers under clean cultivation and black mulch, and the fewest roots under red mulch. Colored mulches influenced the total number of adventitious and lateral roots but not the root system architecture of pepper plants.
variation by mapping quantitative trait loci (QTLs) that control different aspects of root system architecture and development. These studies mostly have been carried out in the model species Arabidopsis thaliana (L.) Heynh ( Fitz-Gerald et al., 2006
significant statistical difference ( P < 0.05). Table 2. Plant resource allocation and root system architecture of large crabgrass grown in a solid-pattern rhizobox filled uniformly with unamended field soil (Control), z field soil with 2% low
deficiency and toxicity in sweetpotato is of fundamental and practical importance in this globally important crop. One of the means that plants adapt to variation in soil nutrient availability is by altering root system architecture (RSA) (reviewed in
study the effect that substrate and pedigree have on root system architecture and to develop molecular markers to breed for root system architecture traits. Seeds were germinated in 3.8-L pots filled with sphagnum peatmoss (peat) in a temperature
Studies have demonstrated that the size of transplanted trees has a measurable impact on establishment rates in the landscape. Larger trees require a longer period of time than smaller trees to produce a root system comparable in spatial distribution to similar sized non-transplanted trees. This lag in redevelopment of root system architecture results in reduced growth that increases with transplant size. Research has demonstrated that smaller transplanted trees become established more quickly and ultimately result in larger trees in the landscape in a few years. Additional studies dispute these findings. This paper provides a review of current research on the effect of tree size on transplant establishment.
In 1999, `Sweet Banana' pepper plants were grown under clean cultivation or SMR—red, silver, or black polyethylene mulches. Plants in each of three replications per treatment were field-set on 15 June. On 22 Sept., plants were excavated, and their root systems were examined. The total number of roots per plant at 5-, 10-, 15-, 20-, and 25-cm depths and 10-, 20-, 30-, 40-, 50-, and 60-cm distances from plant stems were recorded. Distribution and architecture of the root systems also were examined. Plants grown under clean cultivation developed 50 to 60 adventitious roots each, while those grown under red mulch developed about 20, and those under black and silver mulch about nine adventitious roots each. In all treatments, the adventitious roots radiated from the stem at an oblique, downward 35° angle. No plants had vertical roots. Root system architecture was similar among treatments, with 40% of the roots in the upper 5 cm of soil and 70% in the upper 10 cm. Thirty percent of roots were within 10 cm of the plant stem, and 50% were within 20 cm. Nearly 100% of the roots were located within 40 cm of the plant stem. Root count decreased with increasing depth and distance from the plant stem. Plants grown beneath the silver mulch produced the greatest number of lateral roots, followed by plants grown in clean cultivation and under black mulch. Plants grown under red mulch produced the fewest roots. Differences among treatments were significant. Colored mulches influence the total number of adventitious and lateral roots but not the root system architecture of pepper plants.
Quercus falcata acorns were cold-stratified for 120 days and then sown in vermiculite under greenhouse conditions. When radicles were 7 cm long, the root tip was either removed (physically pruned) or dipped in a copper hydroxide solution (copper-treated). Intact root systems were used as control. Seedlings were then moved to a root box to observe root system architectures. The box was built of clear plexiglass 2.5 mm thick, and each face was 25.7 × 35.7 cm. Styrofoam spacers were used to separate faces, and nuts and bolts were placed along edges to hold the root box together. To permit observation of the entire root system, plants were grown in a plane between the plexiglass surface and a nylon sheet that separated roots from the medium (MetroMix 510). At 7, 9, and 11 days after treatment, the entire root system was traced on an acetate sheet, and number of internal and external links and number of secondary and tertiary roots were recorded. Total length, internal and external root links length, were obtained using digital analysis (MacRhizo). Dry weight of roots and shoots was collected at the end of this experiment (day 11). Treatment effects were evident 11 days after treatment. Copper-treated plants had statistically more secondary roots and larger internal link length than control or physically pruned plants. Also, copper-treated plants had smaller mean external link length, showing a more branched root system. Root biomass was similar for all treatments; however, copper-treated plants had smaller root: shoot ratio. This suggests that copper was acting as more than a pruning agent because copper-treated plants showed a different root system architecture compared to physically pruned plants.
Interest in chemical modification of root systems of container-grown trees has increased in recent years with more widespread recognition of implications of root system architecture of container-grown trees on subsequent landscape performance. Initial research on Cu-based latex materials for application to interior container surfaces to avoid circled, matted, and kinked roots at container wall: media interfaces began with small forest tree liners in the late 1970s and early 1980s. Transfer of this technology to horticultural crops followed from the mid-1980s to the present. Testing has spread to a wide range of temperate and tropical landscape trees, shrubs, herbaceous annuals and perennials, interior foliage plants, and vegetable transplants. Inhibition of root elongation after contact with treated container surfaces is via a mild Cu toxicity, frequently resulting in a stimulation of lateral root proliferation proximal to the inhibited root tip, but responses vary with species, cultivar, media composition and pH, and Cu concentration and formulation. Early reports on root architecture effects were predominantly qualitative in nature. Quantitative studies on root architecture within treated containers have been less consistent in responses among species. Improvements in root regeneration, shoot growth, and water relations during post-transplant field establishment of trees grown in Cu-treated vs. non-treated containers have been documented for several species. Ecological (Cu leaching potential), technological (new applications), and economic (profitability) questions have arisen with increased use and availability of Cu-based container treatments and will be discussed.
Low P availability is a primary limitation to plant growth on most native soils. Crop genotypes differ substantially in their ability to grow in low P soils. Understanding the physiological basis for such variation would be useful in developing genotypes with superior P efficiency, which would have utility in low-input systems and might permit more. efficient fertilizer use in high-input systems. In common bean (Phasecolus vulgaris), growth under P stress is reduced because of increased C costs of the root system. Genetic contrasts in P efficiency were not associated with reduced shoot requirement, mycorrhizal associations, chemical interactions with specific soil P pools, or root system size, but were associated with root system architecture. SimRoot, an explicit geometric model of bean root growth, confirmed that architectural traits can influence the relationship of root C costs and P acquisition. Root growth responds dynamically to P stress, through changes in the proliferation of lateral roots and the geotropic response of basal roots. Differences in root architecture arising from these growth responses to P stress may account for genetic differences in P efficiency.