Storage Root Growth Research Articles

Effect of Waste Cooking Oil-Based Composite Materials on Radish Growth and Biochemical Responses

Waste cooking oil poses a serious threat to human health and the environment, both in households and in larger communities. One of the applications of waste cooking oil is composite materials called vegeblocks, which can be used for construction purposes. These composites are formed by the process of polymerisation, esterification and polyesterification. The resulting materials exhibit mechanical strength in line with the requirements for paving blocks. Composite materials that have been annealed for a minimum of 20 h at 200 °C or higher have the highest tensile strength (above 5 MPa). In contrast, composites with the highest flexural strength were obtained after processing at 210 °C for 16 h. The Saxa 2 variety showed the greatest inhibition of storage root growth (almost 43% compared to the control sample), as well as stimulation of root and leaf blade growth (by a maximum of 61.5% and 53.5%, respectively, compared to the control sample). The composite obtained from the maximum process parameters resulted in significant growth of both the root and the green part of both radish varieties by up to 35%. The study showed that the presence of vegeblocks in the plants causes stress conditions, resulting in increased peroxidase content compared to the control sample. The presence of the oil composite in the soil did not increase the amount of catalase in the radish, and even a reduction was observed compared to the control sample.

Evaluation of the effects of elevated CO2 concentrations on the growth of cassava storage roots by destructive harvests and ground penetrating radar scanning approaches.

Cassava (Manihot esculenta Crantz) production will need to be improved to meet future food demands in Sub-Saharan Africa. The selection of high-yielding cassava cultivars requires a better understanding of storage root development. Additionally, since future production will happen under increasing atmospheric CO2 concentrations ([CO2 ]), cultivar selection should include responsiveness to elevated [CO2 ]. Five farmer-preferred African cassava cultivars were grown for three and a half months in a Free Air CO2 Enrichment experiment in central Illinois. Compared to ambient [CO2 ] (~400 ppm), cassava storage roots grown under elevated [CO2 ] (~600 ppm) had a higher biomass with some cultivars having lower storage root water content. The elevated [CO2 ] stimulation in storage root biomass ranged from 33% to 86% across the five cultivars tested documenting the importance of this trait in developing new cultivars. In addition to the destructive harvests to obtain storage root parameters, we explored ground penetrating radar as a nondestructive method to determine storage root growth across the growing season.

Nitrate enhances the secondary growth of storage roots in Panax ginseng

BackgroundNitrogen (N) is an essential macronutrient for plant growth and development. To support agricultural production and enhance crop yield, two major N sources, nitrate and ammonium, are applied as fertilizers to the soil. Although many studies have been conducted on N uptake and signal transduction, the molecular genetic mechanisms of N-mediated physiological roles, such as the secondary growth of storage roots, remain largely unknown. MethodsOne-year-old P. ginseng seedlings treated with KNO3 were analyzed for the secondary growth of storage roots. The histological paraffin sections were subjected to bright and polarized light microscopic analysis. Genome-wide RNA-seq and network analysis were carried out to dissect the molecular mechanism of nitrate-mediated promotion of ginseng storage root thickening. ResultsHere, we report the positive effects of nitrate on storage root secondary growth in Panax ginseng. Exogenous nitrate supply to ginseng seedlings significantly increased the root secondary growth. Histological analysis indicated that the enhancement of root secondary growth could be attributed to the increase in cambium stem cell activity and the subsequent differentiation of cambium-derived storage parenchymal cells. RNA-seq and gene set enrichment analysis (GSEA) revealed that the formation of a transcriptional network comprising auxin, brassinosteroid (BR)-, ethylene-, and jasmonic acid (JA)-related genes mainly contributed to the secondary growth of ginseng storage roots. In addition, increased proliferation of cambium stem cells by a N-rich source inhibited the accumulation of starch granules in storage parenchymal cells. ConclusionThus, through the integration of bioinformatic and histological tissue analyses, we demonstrate that nitrate assimilation and signaling pathways are integrated into key biological processes that promote the secondary growth of P. ginseng storage roots.

Gibberellin Signaling Promotes the Secondary Growth of Storage Roots in Panax ginseng.

Gibberellins (GAs) are an important group of phytohormones associated with diverse growth and developmental processes, including cell elongation, seed germination, and secondary growth. Recent genomic and genetic analyses have advanced our knowledge of GA signaling pathways and related genes in model plant species. However, functional genomics analyses of GA signaling pathways in Panax ginseng, a perennial herb, have rarely been carried out, despite its well-known economical and medicinal importance. Here, we conducted functional characterization of GA receptors and investigated their physiological roles in the secondary growth of P. ginseng storage roots. We found that the physiological and genetic functions of P. ginseng gibberellin-insensitive dwarf1s (PgGID1s) have been evolutionarily conserved. Additionally, the essential domains and residues in the primary protein structure for interaction with active GAs and DELLA proteins are well-conserved. Overexpression of PgGID1s in Arabidopsis completely restored the GA deficient phenotype of the Arabidopsis gid1a gid1c (atgid1a/c) double mutant. Exogenous GA treatment greatly enhanced the secondary growth of tap roots; however, paclobutrazol (PCZ), a GA biosynthetic inhibitor, reduced root growth in P. ginseng. Transcriptome profiling of P. ginseng roots revealed that GA-induced root secondary growth is closely associated with cell wall biogenesis, the cell cycle, the jasmonic acid (JA) response, and nitrate assimilation, suggesting that a transcriptional network regulate root secondary growth in P. ginseng. These results provide novel insights into the mechanism controlling secondary root growth in P. ginseng.

Changes in cell wall components and polysaccharide-degrading enzymes in relation to differences in texture during sweetpotato storage root growth

Sweetpotato has special texture characteristics, which directly affect the eating quality and post-production processing quality of sweetpotato. To investigate the texture change mechanism of sweetpotato during the growth process, this study selected two varieties with significant differences in texture from 35 varieties. The storage roots were sampled at 50, 80, 110, and 140 days after planting. Measure the texture parameters, the cell wall composition content, cell wall-related enzyme activities and the expression of expansin genes of sweetpotato storage roots. The results show that the hardness, adhesiveness and chewiness parameters of ‘Yushu No 10′ were significantly lower than those of ‘Mianfen No 1′, they have significantly different texture properties. In terms of cell wall composition, the soluble pectin content of ‘Yushu No 10′ was more than twice that of ‘Mianfen No 1′, whereas the insoluble pectin content was lower than that of ‘Mianfen No 1′, with the cellulose content of ‘Yushu No 10′ being significantly higher than that of ‘Mianfen No 1′. In terms of cell wall-related enzymes, ‘Yushu No 10′ hardness gumminess and chewiness had a significant correlation with hemicellulose activity, and ‘Mianfen No 1′ had insignificant correlation with four cell wall-related enzymes. Expansin genes were also expressed differently during the various stages of root tubers expansin. The expressions of IbEXP1, IbEXP2 and IbEXPL1 were significantly correlated with the changes in cell wall component content, and were related to the qualitative structure changes. The research conclusion shows that the texture changes during the growth of sweetpotato are related to cell wall composition, cell wall-related enzyme activity changes, and the expression of expansin genes. This study provides theoretical guidance for in-depth study of texture changes of sweetpotato, post-harvest processing and utilization and quality improvement of storage roots.

Plant Biology: Storage Root Growth through Thick and Thin

Embedded within plant stems and roots, the radially dividing cambium controls organ thickening. A study of radish root transcriptomes finds that multiple cambial gene regulatory networks are conserved between radish and the model species Arabidopsis. These results highlight the close relationship between root thickening and environmental responses.

Mining for Candidate Genes Controlling Secondary Growth of the Carrot Storage Root.

Background: Diverse groups of carrot cultivars have been developed to meet consumer demands and industry needs. Varietal groups of the cultivated carrot are defined based on the shape of roots. However, little is known about the genetic basis of root shape determination. Methods: Here, we used 307 carrot plants from 103 open-pollinated cultivars for a genome wide association study to identify genomic regions associated with the storage root morphology. Results: A 180 kb-long region on carrot chromosome 1 explained 10% of the total observed phenotypic variance in the shoulder diameter. Within that region, DcDCAF1 and DcBTAF1 genes were proposed as candidates controlling secondary growth of the carrot storage root. Their expression profiles differed between the cultivated and the wild carrots, likely indicating that their elevated expression was required for the development of edible roots. They also showed higher expression at the secondary root growth stage in cultivars producing thick roots, as compared to those developing thin roots. Conclusions: We provided evidence for a likely involvement of DcDCAF1 and/or DcBTAF1 in the development of the carrot storage root and developed a genotyping assay facilitating the identification of variants in the region on carrot chromosome 1 associated with secondary growth of the carrot root.

Involvement of nitrogen in storage root growth and related gene expression in sweet potato (Ipomoea batatas).

Nitrogen (N) could affect storage root growth and development of sweet potato. To manage external N concentration fluctuations, plants have developed a wide range of strategies, such as growth changes and gene expression. Five sweet potato cultivars were used to analyse the functions of N in regulating storage root growth. Growth responses and physiological indicators were measured to determine the physiological changes regulated by different N concentrations. Expression profiles of related genes were analysed via microarray hybridization data and qRT-PCR analysis to reveal the molecular mechanisms of storage root growth regulated by different N concentrations. The growth responses and physiological indicators of the five cultivars were changed by N concentration. The root fresh weight of two of the sweet potato cultivars, SS19 and GS87, was higher under low N concentrations compared with the other cultivars. SS19 and GS87 were found to be having greater tolerance to low N concentration. The expression of N metabolism and storage root growth related genes was regulated by N concentration in sweet potato. These results reveal that N significantly regulated storage root growth. SS19 and GS87 were more tolerant to low N concentration and produced greater storage root yield (at 30 days). Furthermore, several N response genes were involved in both N metabolism and storage root growth.

Crop growth and development dynamics of two fodder beet (Beta vulgaris L.) cultivars sown on different dates in New Zealand

ABSTRACT Two fodder beet (Beta vulgaris L.) cultivars (‘Rivage’ and SF Brigadier™) were evaluated in a field experiment to quantify the effect of cultivar and sowing date on growth physiology. The crops were sown on 19 September, 17 October, 17 November and 15 December in 2014. Crops were sequentially harvested and separated into storage root, leaf blade and petiole for analysis. Fodder beet growth was sigmoidal; the growth of leaf blades and petioles dominated the lag phase while storage root growth dominated the exponential phase. The appearance of the 25th leaf marked the beginning of the exponential phase. The maximum growth rate was not affected by the cultivar or sowing date. Total dry matter (DM) yield was the same for September- and October-sown crops (2444 ± 164 g DM m−2); showing little advantage of early sowing because cold temperatures slowed canopy development. The November- and December-sown crops produced 18% and 30% lower yield than the October-sown crops. ‘Rivage’ partitioned 5% greater DM to the storage root, an indication of greater sink strength, than SF Brigadier. Information on the pattern of growth can aid management decisions for optimising yield, and is valuable for the improvement of fodder beet models.

A low-cost aeroponic phenotyping system for storage root development: unravelling the below-ground secrets of cassava (Manihot esculenta)

BackgroundRoot and tuber crops are becoming more important for their high source of carbohydrates, next to cereals. Despite their commercial impact, there are significant knowledge gaps about the environmental and inherent regulation of storage root (SR) differentiation, due in part to the innate problems of studying storage roots and the lack of a suitable model system for monitoring storage root growth. The research presented here aimed to develop a reliable, low-cost effective system that enables the study of the factors influencing cassava storage root initiation and development.ResultsWe explored simple, low-cost systems for the study of storage root biology. An aeroponics system described here is ideal for real-time monitoring of storage root development (SRD), and this was further validated using hormone studies. Our aeroponics-based auxin studies revealed that storage root initiation and development are adaptive responses, which are significantly enhanced by the exogenous auxin supply. Field and histological experiments were also conducted to confirm the auxin effect found in the aeroponics system. We also developed a simple digital imaging platform to quantify storage root growth and development traits. Correlation analysis confirmed that image-based estimation can be a surrogate for manual root phenotyping for several key traits.ConclusionsThe aeroponic system developed from this study is an effective tool for examining the root architecture of cassava during early SRD. The aeroponic system also provided novel insights into storage root formation by activating the auxin-dependent proliferation of secondary xylem parenchyma cells to induce the initial root thickening and bulking. The developed system can be of direct benefit to molecular biologists, breeders, and physiologists, allowing them to screen germplasm for root traits that correlate with improved economic traits.

Drought Avoidance and Phenotypic Flexibility of Sweet Potato (Ipomoea batatas (L.) Lam.) Under Water Scarcity Conditions

Sweet potato (Ipomoea batatas (L.) Lam.) is an important staple food in several regions of the world. Water scarcity is the most devastating abiotic stress, with a great impact on crop productivity, food security, and subsistence. Drought restricts the nutrient intake and transport into the plant. Tolerant crops have morphological mechanisms of drought avoidance and/or phenotypic flexibility, showing also good water and nutrient efficiency. However, that information is scarce for sweet potato, which is usually based on physiological traits of plant productivity. Here, we show the physiological responses of eight sweet potato accessions subjected to a 3 months’ drought period, by recording their differences for nutrient and leaf chlorophyll content, biomass and stress level. Our results showed that the differences in water use efficiency (WUE, +68.1%), chlorophyll content index (CCI, -5.3%), total plant biomass (TPB, -55.4%), nutrient efficiency (NER, +38.1%) and nutrient harvest index (NHI, +2.9%) where significantly correlated with the water regime. The water shortage led to a drought avoidance response, with TPB loss in all accessions. Distinct phenotypic flexibility responses were also recorded and explained by the root:shoot ratio (R:S) and stress index (SI) variation of the storage root and shoot growth. This information could be relevant for the development of sweet potato breeding programs, adapting this crop to climate change.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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A novel effect of glycine on the growth and starch biosynthesis of storage root in sweetpotato (Ipomoea batatas Lam.)

Sweetpotato (Ipomoea batatas Lam.) plays an indispensable role in feed, starch-based industries and ethanol biofuel production. Few studies have investigated on how external amino acids affect the growth and production of sweetpotato. In the study, we evaluated morphological, physiological and molecular effects of external glycine (Gly) on the root growth and starch metabolism of sweetpotato, Xushu16. At morphological level, the Xushu16 with Gly stimuli had larger plant biomass than that under control condition. At physiological level, the photosynthesis strength of the Xushu16 with Gly treatments showed significant differences relative to those under control condition. The relative content of plant hormone and starch in storage roots was higher under Gly conditions than that under control condition. At molecular level, a total of 4836 differentially expression genes were identified in the storage roots with different Gly treatments by RNA-Seq. Among them, as many as 1830 genes were involved in carbohydrate metabolism, which held maximum proportion among all the DEGs. Further, a few genes involved in starch biosynthesis were proved to be Gly-induced significantly by RT-qPCR. All the results indicated extrinsic Gly promotes the growth of storage roots by strengthening photosynthesis and increasing plant hormone, and enhances starch biosynthesis of storage roots by accelerating carbohydrate metabolism and regulating the expression of starch-related genes.

Growth rates and yields of cassava at different planting dates in a tropical savanna climate

ABSTRACT: Details on growth and yield for cassava planted on different dates are useful for determining suitable genotypes for particular growing seasons. Our aim was to study growth and yield of cassava planted on different dates. Four cassava genotypes (Kasetsart 50, Rayong 9, Rayong 11 and CMR38-125-77) were evaluated using a randomized complete block design (RCBD) with four replications in six growing periods (20 Apr, 25 May, 30 June, 5 Oct, 10 Nov and 15 Dec 2015-2016) at Khon Kaen, Thailand. Soil properties were determined prior to planting, and crop traits and weather data were recorded. The six planting dates had a statistically significant effect on all crop traits. Low temperatures and solar radiation related to low biomass accumulation rates and short periods of linear phases for total crop and storage root dry weights with the 30 June planting date. CMR38-125-77 is likely to be a good genotype with respect to total crop and storage root dry weights at final harvest for almost all growing dates, except for the 20 Apr. Leaf area index (LAI) at 120, 240 and 300 days after planting (DAP), specific leaf area (SLA) at 120 DAP, storage root growth rate (SRGR) during 300-360 DAP and leaf growth rate (LGR) during 60-120 and 300-360 DAP were the components for the physiological determinants of total crop and storage root dry weight. The relationship between these physiological traits and storage root could be useful for cassava breeding.

The anti-ethylene growth regulator silver thiosulfate (STS) increases flower production and longevity in cassava (Manihot esculenta Crantz)

Cassava, which produces edible starchy roots, is an important staple food for hundreds of millions of people in the tropics. Breeding of cassava is hampered by its poor flower production, flower abortion, and lack of reproductive prolificacy. The current work determined that ethylene signalling affects floral development in cassava and that the anti-ethylene plant growth regulator silver thiosulfate (STS) mitigates the effects of ethylene on flower development. STS did not affect the timing of flower initiation, but improved early inflorescence and flower development as well as flower longevity such that flower numbers were increased. STS did not affect shoot and storage root growth. Studies of silver accumulation and treatment localization support the hypothesis that the beneficial effects of STS are confined to tissues of the shoot apex. The most effective timing of application was before inflorescence appearance extending to post-flower appearance. Based on this work a recommended protocol for STS use was developed. This work has the potential to improve methods for enhancing cassava flower development in breeding nurseries and thereby synchronize flowering of desired parents and enable the production of abundant progeny of desired crosses.

Extended Utilization of Constraint-Based Metabolic Model in a Long-Growing Crop

The constraint-based rMeCBM-KU50 model of cassava storage root growth was analyzed to evaluate its sensitivity, with respect to reaction flux distribution and storage root growth rate, to changes in model inputted data and constraints, including sucrose uptake rate-related data—photosynthetic rate, total leaf area, total photosynthetic rate, storage root dry weight, and biomass function-related data. These mainly varied within ±90% of the model default values, although exceptions were made for the carbohydrate (−90% to 8%) and starch (−90% to 9%) contents. The results indicated that the predicted storage root growth rate was highly affected by specific sucrose uptake rates through the total photosynthetic rate and storage root dry weight variations; whereas the carbon flux distribution, direction and partitioning inclusive, was more sensitive to the variation in biomass content, particularly the carbohydrate content. This study showed that the specific sucrose uptake rate based on the total photosynthetic rate, storage root dry weight, and carbohydrate content were critical to the constraint-based metabolic modeling and deepened our understanding of the input–output relationship—specifically regarding the rMeCBM-KU50 model—providing a valuable platform for the modeling of plant metabolic systems, especially long-growing crops.

Potential for Expanding Cassava Production, Farmer Income in Thailand

Cassava (Manihot esculenta) is a multipurpose crop. The plant produces a tuber that is edible with proper preparation and is a staple carbohydrate, and the cassava starch is also used to make the tapioca pearls in your pudding cup. In addition to its use as food and animal feed, there has been an increasing interest in using cassava as a biofuel. In Thailand, a major producer and exporter of cassava, the crop can be grown year-round. Typically, cassava is grown in upland areas under rainfed conditions and harvested 12 to 18 months after planting. However, research has shown that farmers can use rice paddy fields in the off-season to produce a cassava crop. This is because rice paddy fields are left fallow from roughly December through August. This is a notably shorter growing season and does result in cassava with lower starch yields. Nevertheless, using rice paddy fields to increase cassava production could increase production and income for farmers on land that would not otherwise be used for production. Poramate Banterng, a crop breeder who works with the cassava breeding program in Khon Kaen University, and colleagues recently conducted a study in Thailand evaluating the performance of four cassava genotypes grown in rice paddy fields during the off-season. The results of this research were recently published in Crop Science (http://doi.org/10.2135/cropsci2018.07.0435). Four cassava genotypes were grown at five sites in Thailand. The four genotypes were selected based on maturity and aboveground structure (i.e., branching), including medium maturity and branching (Kasetart 50), late maturity and nonbranching (Rayong 9), late maturity and branching (Rayong 11), and early maturity and branching (CMR38-125-77). Cassava was planted in December and harvested in June. During the study, weather conditions were monitored at each site, and crop data were collected at 30-day intervals including the final harvest at 180 days after planting. Crop data included leaf area, growth rates (leaf, stem, and root), and root starch content. The main finding of this study was that the genotype selected for early maturity and branching characteristics (CMR38-125-77) had the best performance. This genotype had a higher mean performance and stability for storage root fresh weight, storage root dry weight, and total dry weight when compared with the other genotypes. Banterng points out that collecting data throughout the growing season helped in identifying physiological determinants of both storage root yield and total biomass; for example, the change in net assimilation rate from 120 to 180 days after planting and the change in storage root growth rate from 90 to 180 days after planting. Understanding how these traits relate to cassava biomass could aid in selecting and developing cassava that can be grown in rice paddy fields during the off-season. Three different land areas for crops production. Cassava growing period in paddy field after rice. “The results from this study indicate that cassava may be a viable alternative crop in upper paddy fields during the off-season of rice,” Banterng says, “and this could help to increase food, feed, and bioenergy production in Thailand.” Banterng also recognizes that growing cassava in rice paddy fields rather than leaving them fallow could affect the nutrient balance, resulting in a need for monitoring soil fertility and possibly the addition of fertilizers. “Presently, some of the farmers in Thailand are interested in this growing system because they can earn more money from their own land areas during the dry season. Therefore, breeding for early bulking and drought tolerances and [studying] nutrient balance and fertilizer management for this growing system are also necessary.” If a large number of farmers were to implement this practice, there will be a need for research to determine the best management practices to sustain both cassava and rice production in this region. Check out the original full-length article, “Cassava Growth Analysis of Production during the Off-Season of Paddy Rice,” in Crop Science: http://doi.org/10.2135/cropsci2018.07.0435.

Cassava Growth Analysis of Production during the Off‐Season of Paddy Rice

Cassava (Manihot esculenta Crantz) grown in upper paddy fields after rice (Oryza sativa L.) could increase cassava yield and improve land use efficiency. The objective of this study was to evaluate growth, yield, and starch content of four cassava genotypes grown after the harvest of rice in upper paddy fields in Thailand. Four cassava genotypes—cultivars Kasetsart 50, Rayong 9, and Rayong 11—and line CMR38‐125‐77 were evaluated during the 2015–2016 and 2016–2017 growing seasons for five environments. Each experiment had a randomized complete block design with four replications. Soil characteristics were assessed prior to planting, and crop growth and development and local weather conditions were recorded during the experiments. Environment affected all traits, but genotype and genotype × environment effects were nonsignificant for starch content at 180 d after planting (DAP) and for leaf growth rate (LGR) at 120 to 180 DAP. Average storage root dry weights across five environments were 4301, 3933, 3128, and 5824 kg ha−1 for Kasetsart 50, Rayong 9, Rayong 11, and CMR38‐125‐77, respectively. CMR38‐125‐77 was the most stable genotype for storage root fresh and dry weights, and total dry weight. Physiological determinants of both storage root yield and total biomass of cassava were crop growth rate (CGR) and net assimilation rate (NAR) for 30 to 90 DAP and LGR, stem growth rate (SGR), CGR, and NAR for 120 to 180 DAP, as well as storage root growth rate (SRGR) for 90 to 180 DAP. Leaf growth rate during 120 to 180 DAP is likely to be a new criterion for supporting cassava varietal selection. This investigation showed the feasibility of growing cassava between paddy rice seasons.

Understanding carbon utilization routes between high and low starch-producing cultivars of cassava through Flux Balance Analysis

Analysis of metabolic flux was used for system level assessment of carbon partitioning in Kasetsart 50 (KU50) and Hanatee (HN) cassava cultivars to understand the metabolic routes for their distinct phenotypes. First, the constraint-based metabolic model of cassava storage roots, rMeCBM, was developed based on the carbon assimilation pathway of cassava. Following the subcellular compartmentalization and curation to ensure full network connectivity and reflect the complexity of eukaryotic cells, cultivar specific data on sucrose uptake and biomass synthesis were input, and rMeCBM model was used to simulate storage root growth in KU50 and HN. Results showed that rMeCBM-KU50 and rMeCBM-HN models well imitated the storage root growth. The flux-sum analysis revealed that both cultivars utilized different metabolic precursors to produce energy in plastid. More carbon flux was invested in the syntheses of carbohydrates and amino acids in KU50 than in HN. Also, KU50 utilized less flux for respiration and less energy to synthesize one gram of dry storage root. These results may disclose metabolic potential of KU50 underlying its higher storage root and starch yield over HN. Moreover, sensitivity analysis indicated the robustness of rMeCBM model. The knowledge gained might be useful for identifying engineering targets for cassava yield improvement.

Reprogramming of the cambium regulators during adventitious root development upon wounding of storage tap roots in radish (Raphanus sativus L.).

ABSTRACTCambium contains a stem cell population that produces xylem and phloem tissues in a radial direction during the secondary growth stage. The growth of many storage roots, including in the radish, Raphanus sativus L., also depends on cambium. Interestingly, we observed numerous adventitious roots (ARs) emerging from the cambia of cut surfaces when the bases of radish storage tap roots were removed. Previous studies in Arabidopsis showed that the WOX11/12 pathway regulates AR initiation and meristem establishment in an auxin-dependent manner. Here, we provide evidence indicating the evolutionary conservation of the WOX11/12 pathway during the AR development in radishes. Additionally, we found that expression of two cambium regulators, PXY and WOX4, is induced in the cambium regions that are connected to emerging ARs via vascularization. Both AR formation and genes associated with this were induced by exogenous auxin. Our research suggests that some key cambium regulators might be reprogrammed to aid in the AR development in concert with the WOX11/12 pathway.This article has an associated First Person interview with the first author of the paper.

Root zone temperature alters storage root formation and growth of sweetpotato

AbstractLarge mounds amended with plant residues are a common cultivation method for sweetpotato (Ipomoea batatas) in the western parts of the Papua New Guinea highlands, with a suggested benefit of elevated root zone temperature (RZT) from decomposition. This study aimed to evaluate whether RZT affects the formation and growth of sweetpotato storage roots. Experiments evaluated the effects of a constant elevated RZT on the Beauregard cultivar and of a short‐term increase in RZT on the Beauregard and Northern Star cultivars. Plants were grown in 18‐L pots divided into a control compartment (constant RZT at 20°C) and a treated compartment (RZT at 30, 40 or 50°C). Constant elevated RZT was maintained until harvest, while short‐term increase in RZT occurred in weeks 2 and 3 only. Constant elevated RZT did not affect the total number of storage roots, but RZT of 30°C and above reduced the dry‐biomass of storage roots. The short‐term increase in RZT did not alter the total number or dry‐biomass of storage roots in Beauregard, while both of these attributes were reduced at RZT of 40°C or above in Northern Star. Elevated RZT inhibited dry‐biomass accumulation of storage root, with a more pronounced impact at constant elevated RZT. These results demonstrate that any benefits of the mound culture on sweetpotato yield production do not arise through the influence of temperature elevation.