Total Number Of Lateral Roots Research Articles

The caleosin RD20/CLO3 regulates lateral root development in response to abscisic acid and regulates flowering time in conjunction with the caleosin CLO7

The caleosins are encoded by multi-gene families in Arabidopsis thaliana and other plant species. This work investigates the role of two family members, RD20/CLO3 and CLO7, in flowering transition and in root development in response to ABA treatment. Gene expression of the caleosin RD20/CLO3 is induced by ABA in the root tissues and RD20/CLO3 has a negative affect on the total number of lateral roots as well as the length of the lateral roots in response to ABA treatment. The rd20/clo3 mutant has more and longer lateral roots in response to ABA treatment compared to the wild-type, showing that RD20/CLO3 plays a role in the ABA signaling pathway affecting this trait. In contrast, the caleosin CLO7 is not expressed in the roots and does not affect root architecture in response to ABA treatment. The disruption of both RD20/CLO3 and CLO7 together causes a dramatic early-flowering phenotype under long-day conditions, whereas single mutations in these genes do not affect flowering time under these conditions. Both yeast two-hybrid and bimolecular fluorescence complementation showed that both RD20/CLO3 and CLO7 interact with each other and can form homodimers and heterodimers. Taken together, these findings suggest that members of the caleosin gene family play both different and redundant roles in plant development.

Application of an Improved 2-Dimensional High-Throughput Soybean Root Phenotyping Platform to Identify Novel Genetic Variants Regulating Root Architecture Traits.

Nutrient-efficient root system architecture (RSA) is becoming an important breeding objective for generating crop varieties with improved nutrient and water acquisition efficiency. Genetic variants shaping soybean RSA is key in improving nutrient and water acquisition. Here, we report on the use of an improved 2-dimensional high-throughput root phenotyping platform that minimizes background noise by imaging pouch-grown root systems submerged in water. We also developed a background image cleaning Python pipeline that computationally removes images of small pieces of debris and filter paper fibers, which can be erroneously quantified as root tips. This platform was used to phenotype root traits in 286 soybean lines genotyped with 5.4 million single-nucleotide polymorphisms. There was a substantially higher correlation in manually counted number of root tips with computationally quantified root tips (95% correlation), when the background was cleaned of nonroot materials compared to root images without the background corrected (79%). Improvements in our RSA phenotyping pipeline significantly reduced overestimation of the root traits influenced by the number of root tips. Genome-wide association studies conducted on the root phenotypic data and quantitative gene expression analysis of candidate genes resulted in the identification of 3 putative positive regulators of root system depth, total root length and surface area, and root system volume and surface area of thicker roots (DOF1-like zinc finger transcription factor, protein of unknown function, and C2H2 zinc finger protein). We also identified a putative negative regulator (gibberellin 20 oxidase 3) of the total number of lateral roots.

Development of Root Architecture in Thirty-seven Tree Species of Field Grown Nursery Stock1

AbstractThe number and size of lateral roots of a tree seedling can be evaluated visually, and could potentially be used to select plants with better root systems early in nursery production. To evaluate how root architecture develops in young trees, root architecture of 37 species of trees was compared at two stages of development: as harvested seedlings, and then one year after replanting. The total number of lateral roots and the number of roots >2mm (0.08 in) diameter that were present on the portion of the taproot remaining on seedlings after standard root pruning were recorded. Neither could consistently predict the number of lateral roots on the root system one year after replanting. Development of roots (sum of diameters) regenerated from the cut end of the seedling taproot was equal or greater than lateral root development in 84 percent of evaluated species. Even when regenerated root development was significantly less than lateral root development, the regenerated roots still comprised up to 44 percent of the root system. Regenerated roots from the cut end of the taproot can become a major component of the architecture of the structural root system in nursery stock.Index words: structural roots, nursery production, root regeneration.Species used in this study: European black alder (Alnus glutinosa Gaertn.), green ash (Fraxinus pennsylvanica Marshall), quaking aspen (Populus tremuloides Michx.), European white birch. (Betula pendula Roth), river birch (Betula nigra L.), black locust (Robinia pseudoacacia L.), northern catalpa (Catalpa speciosa (Warder) Warder ex Engelm.), Mazzard cherry [Prunus avium [L.) L.], chokecherry (Prunus virginiana L.), American elm (Ulmus americana L.), Siberian elm (Ulmus pumilia L.), goldenchain tree (Laburnum anagyroides Medik.), northern hackberry (Celtis occidentalis L.), Cockspur hawthorn (Crateagus crus-galli L.), single seed hawthorn (Crateagus monogyna Jacq.), honeylocust (Gleditsia tricanthos L.), Japanese pagodatree [Sophora japonica (L.) Schott], Katsura tree (Cercidiphyllum japonicum Siebold & Zucc.), Kentucky coffee tree [Gymnocladus dioicus (L.) K. Koch], littleleaf linden (Tilia cordata Mill.), boxelder (Acer negundo L.), hedge maple (Acer campestre L.), Norway maple (Acer platanoides L.), red maple (Acer rubrum L.), silver maple (Acer saccharinum L.), sugar maple (Acer saccharum Marshall), sycamore maple (Acer pseudoplatanus L.), English Oak (Quercus robur L.), northern red oak (Quercus rubra L.), Siberian peashrub (Caragana arborescens Lam.), American plum (Prunus Americana Marshall ), Myrobalan plum (Prunus cerasifera Ehrh.), redbud (Cercis Canadensis L.), Russian olive (Elaeagnus angustifoliaI L.), tuliptree (Liriodendron tulipifera L.), black walnut (Juglans nigra L.), Japanese zelkova (Zelkova serrata (Thunb.) Makino).

The blue light receptor Phototropin 1 suppresses lateral root growth by controlling cell elongation

We investigated the relationship between the blue light receptor phototropin 1 (phot1) and lateral root growth in Arabidopsis thaliana seedlings. Fluorescence and confocal microscopy images, as well as PHOT1 mRNA expression studies provide evidence that it is highly expressed in the elongation zone of lateral roots where auxin is accumulating. However, treatment with the auxin transport inhibitor N-1-naphthylphthalamic acid significantly reduced PHOT1 expression in this zone. In addition, PHOT1 expression was higher in darkness than in light. The total number of lateral roots was higher in the phot1 mutant than in wild-type Arabidopsis. Cells in the elongation zone of lateral roots of the phot1 mutant were longer than those of wild-type lateral roots. These findings suggest that PHOT1 plays a role(s) in elongation of lateral roots through the control of an auxin-related signalling pathway.

Modification of root architecture in woody plants is possible for the presence of two different mechanisms of lateral root production: The effect of slope in Spartium junceum L. seedlings

This paper investigates the modification of root architecture of Spartium junceum L. seedlings grown in slope condition. It is reported that 50% of the total number of lateral roots are concentrated in few centimetres of the taproot near the collar. The anatomical analysis of transverse sections along the taproot axis reveals that this taproot zone is characterised by two types of lateral roots: one with a trace extending to the centre of the vascular cylinder by following the path of a medullar ray; one with a trace which ends in the vascular cambium. The first type may be lateral roots originated from the taproot primary structure; the second type seems to be lateral roots developing later when a secondary structure has completely substituted the primary structure. The emission of this second type of lateral roots seems to be strongly controlled by environmental conditions with considerable consequences upon the overall root architecture. In the example reported in this paper, young plants growing under mechanical stress due to a slope develop asymmetric root architecture with lateral roots elongating in two prevalent directions: up-slope or down-slope. This asymmetric architecture is produced in the zone of the taproot where a secondary structure is present and represents the plant response to the need of increasing its anchorage strength.

KNAT6 gene of Arabidopsis is expressed in roots and is required for correct lateral root formation.

As part of a programme to determine whether root development requires a pathway involving KNOTTED-like homeobox ( KNOX ) genes, we cloned the KNAT6 cDNA, a member of the KNOX gene family in Arabidopsis, from root tissue. The KNAT6 cDNA is represented by two isoforms, suggesting that the KNAT6 transcript is subject to alternative splicing. Promoter-reporter and RT-PCR analysis confirms expression of the KNAT6 gene in roots, and in particular in the phloem tissue close to the site of lateral root initiation, though not in the primary or lateral root meristem. The KNAT6 gene promoter activity is altered in pattern by treatment with exogenous auxin and in the rooty mutant background, with expression shifting distally in the root. In contrast, exogenous cytokinin suppresses KNAT6 promoter activity. KNAT6::GFP fusion protein is localized to the nucleus, consistent with the predicted function of KNAT6 as a transcription factor. Over-expression of the more abundant shorter isoform of the KNAT6 cDNA, but not of the less abundant longer form, leads to a lobed leaf phenotype, but no consistently aberrant root phenotype. Down-regulation of KNAT6 expression by RNA interference was associated with an increased total number of lateral roots. These data indicate a role for KNAT6 in modulating lateral root formation.

Water deficit accelerates determinate developmental program of the primary root and does not affect lateral root initiation in a Sonoran Desert cactus (Pachycereus pringlei, Cactaceae)

Determinate root growth is an important adaptation feature for seedling establishment in some Cactaceae. We show that seedlings of Pachycereus pringlei have primary roots with a stable determinate developmental program. How water stress affects determinate root growth and lateral root development has not been studied. Here we address this question. Root growth was analyzed in plants growing in vitro under well-watered and water-deficient (created by polyethylene glycol) growth conditions. Under severe water stress roots terminated their growth earlier and the rate of growth was significantly decreased as a result of inhibition of both cell elongation and cell production. Under severe water stress the number of lateral roots and primordia per millimeter of primary root was 1.5-1.7 times greater than under well-watered conditions; however, the total number of lateral roots and primordia was the same under all conditions. Lateral roots resembled root spurs found in some Opuntioideae. Analysis of the dynamics of meristem exhaustion indicated that initial-cell activities are required for the maintenance of proliferation before meristem exhaustion. We conclude that lateral root formation is a stable developmental process resistant to severe water stress and that water stress accelerates the determinate developmental program of the primary root. Both of these features appear to be important for successful seedling establishment in a desert.

Root System Development of Japonica-Indica Hybrid Cultivars. 2. Branching habit.

Root system development of japonica-indica hybrid rice cultivars (J-IH : Milyang 23, Suwon 258) was compared with that of japonica-type cultivars (JT: Nipponbare, Koshihikari) with reference to branching habit from the viewpoint of developmental morphology. The four cultivars were grown in 45-liter polyethylene containers with paddy field soil and the plants with their root systems were carefully dug up at the grain-filling stage. After careful washing, the main stems of each cultivar were divided into each phytomer and the number, diameter and length of both crown and lateral roots were recorded together with their node position. From these data, the root dimensions (total number of lateral roots, total roots surface area and total root volume) were estimated for each crown root. The results indicated that lateral root development of J-IH was more vigorous than that of JT, especially in the higher phytomers formed after the panicle initiation stage. Such vigorous root branching in J-IH was mainly attributed to an increase in the number of second-order lateral roots. Detailed examination showed that the L-type first-order lateral roots were longer and the density of both L-type first-order and S-type second-order lateral roots were higher in J-IH than in JT. Thus, the root system of J-IH was characterized by long and dense L-type first-order lateral roots and large volume of S-type second-order lateral roots due to their high density. Results of this study suggest that the root system of J-IH increases the total length and surface area, by developing many S-type sedond order lateral roots, which may be related to their high-yield of J-IH.

Comparative studies on the fine root status of healthy and declining spruce and beech trees in the Bavarian Alps and occurrence of Phytophthora and Pythium species

Investigations on root and crown status of spruce and beech were carried out on selected trees in the ‘Werdenfelser Land’ area (Bavarian Alps, Southern Germany). In addition, the association of fine root pathogens of the genera Phytophthora and Pythium with the trees’ rhizosphere was studied. In a variety of stands representing various site conditions, soil and root samples were taken from 12 spruce (Picea abies) pairs and eight beech (Fagus sylvatica) pairs. Each pair consisted of a healthy and a declining tree as indicated by crown transparency. The root status was characterized using a set of parameters, and correlations between crown and fine root status were observed. In spruce, most parameters decreased significantly with increasing crown transparency, whereas in beech, correlations were less pronounced. The total number of lateral roots per cm small root (diameter 2–5 mm) was significantly lower in both species for declining trees compared to healthy trees. Pythium spp. were isolated from 15 of 24 soil samples taken from under spruce, and from eight of 16 samples from under beech. Phytophthora citricola was found in two beech stands only. Among the isolated species, Pythium anandrum, Pythium inflatum and Pythium acrogynum were identified according to morphological features. After polymerase chain reaction‐restriction fragment length polymorphism analysis, residual Pythium isolates were assigned to four different groups. No crown transparency‐dependent differences in isolation frequency were found. In soil infestation tests, all species tested caused root damage on both young spruce and beech plants, with P. citricola being the most aggressive pathogen. Additionally, Pythium‐infected beeches showed severe leaf chloroses and necroses. Due to their low isolation frequency, Phytophthora spp. are not considered to play a major role in the decline of spruce and beech in the investigated area. Pythium spp., however, were isolated frequently, showed pathogenicity towards the fine roots of spruce and beech, and are therefore considered to be at least contributing factors in the decline of Bavarian mountain forests.

Colonization of roots of subterranean clover cultivars by virulent and avirulent races of Phytophthora clandestina

The colonization of the roots of four cultivars of subterranean clover by isolates representing four races of Phytophthora clandestina was studied. There was a highly significant race × cultivar interaction in the growth of inoculated tap roots and the degree of colonization of roots by the pathogen. While all races were able to infect the roots of all cultivars tested, roots of the susceptible cultivars were colonized more rapidly and extensively than those of the resistant cultivars. In compatible combinations, fungal colonization extended for a few centimetres in the tap root and lateral roots in the moderately susceptible cultivars Trikkala and Meteora, or throughout the whole root system leading to the death of the host in the very susceptible cultivar Woogenellup. In contrast, limited fungal colonization of the tap root and lack of extension of the fungus into lateral roots was typical of incompatible combinations. In all cultivars, lateral roots were as susceptible to infection as tap roots. The number of lateral roots of Woogenellup was significantly reduced by infection. However, neither the rate of lateral root formation nor the total number of lateral roots of Seaton Park, Meteora and Trikkala was reduced by infection with virulent or avirulent races of the pathogen.

Lateral root formation in pine seedlings

The effect of stimulating and inhibitory factors on the development of lateral roots was studied in Pinus pinea seedlings grown in a nutrient solution. In an intact root system, only 10–15% of the emerging lateral roots continue to elongate. Removing the tap root tip increased the number and length of the elongating lateral roots but the total number of the lateral roots remained unchanged. The timing of removal of the tap root tip seems to be an important factor in lateral root development. The earlier the removal of the tap root tip, the more lateral roots will elongate. Regardless of the remaining length of the tap root following removal of the tap root tip, lateral root elongation will occur particularly in the youngest lower segment. Removal of cotyledons had a greater inhibitory effect on lateral root development than on tap root growth. The total number of lateral roots and the number of elongating lateral roots were greatly reduced by removal of cotyledons, particularly in seedlings with an intact root system. A decrease in the dry weight of the root system paralleled the reduction in lateral root development. The data indicate that in P. pinea seedlings, factors stimulating root branching originate in the shoot whereas inhibitory factors originate in the tap root tip. Lateral root elongation seems to be the limiting factor in the development of a branched root system.

The Control of Lateral Root Development in Cultured Pea Seedlings. I. The Role of Seedling Organs and Plant Growth Regulators

Experiments were conducted to determine the influence of seedling organs on lateral root development in Pisum sativum `Alaska.' The cotyledons, root tip, and epicotyl were excised from seedlings containing roots of less than 3 cm. In some cases, plant growth regulators or nutritional factors were substituted for the excised organs. The number of emerged and initiated lateral roots was counted after 7 days. Cotyledon removal completely inhibited lateral root emergence and reduced the total number of initiated laterals by 40%. Cotyledon removal did not alter the number of laterals initiated per cm of primary root. Epicotyl removal reduced the number of emerged lateral roots but not the total number initiated. Root tip removal slightly increased the total number of lateral roots formed and emerged from the root region remaining after tip excision. Sucrose, nicotinic acid, pyridoxine, and thiamine did not promote lateral root emergence when provided as cotyledon substitutes. Growth regulator substitutions for...

Studies on the lateral root formation in rice plant : (I) Lateral root formation under conditions of nutritive deficiency

This paper dealt mainly with the effects of nutritive deficiency upon the formation and physiological characteristics of lateral roots in rice plant. Thirty days old seedlings of the variety Norin No. 1 were grown in culture solutions, from which main nutritive elements such as N, P or K was remorvd respectively (Table 1). Plants were sampled 1 month later for the investigations of ecological characteristics of their primary and secondary roots. Main results were as follows: (1) Under conditions of abnormal nutrition, number of primary roots, especially of the newly emerged ones (A class root), decreased in contrast to those of more aged roots (B, C, D and E classed). The length of all roots classified was almost reversely circumstanced as compared with numbers. The root diameter increased in general (Table 2). (2) Total number of lateral roots per primary root and their density increased particularly in B and C class roots, when plants were affected by abnormal nutritions (Table 2). Lateral roots showed a tendency to appear near the tip of a primary root in those cases (Fig. 2). In addition to this experiment, the effects of nitrogen deficiency on lateral roots of the seedlings were examined. From results of this experiment, it was concluded that their lateral roots were similarly increased by the deficiency of the element (Fig. 4). Moreover, physiologically abnormal branch roots (c and t1), showing less TTC reducing activity (Fig. 3), increased in such a case (Fig. 5).