ASHS 2025 Conference

A forum for discussion of potential collaborations with regards to plant growth and culture – i.e. propagation, root growth, water management, weed control, PGRs, plant nutrition, etc.

The most economically important physiological process in sweetpotato is storage root initiation. The number of adventitious roots (ARs) that undergo storage root initiation can vary within and among individual plants. This extends to entire fields, which can vary in storage root yield by up to 50%. This unpredictability is further compounded by the fact that crop yield can only be evaluated post-factum and above-ground growth frequently provides little or no indication of productivity in commercial production settings. Significant progress has been achieved in understanding the environmental, physiological, and molecular cues of storage root formation but current evidence cannot be reconciled with root system architecture variability. Functional-Structural Plant Models (FSPM) such as OpenSimRoot are used to explore and understand the complex interactions among morphological and architectural traits, environment variables, and source-sink relations. OpenSimRoot is capable of simulating spatiotemporal dynamics of plant growth, including 3D root architecture, nutrient and water acquisition, and carbon processes underlying plant growth, but requires extensive parameterization. Here we describe the parameterization of OpenSimRoot to model the timing of storage root initiation and initial bulking stages. The model was parameterized using data from sweetpotato cultivar ‘Beauregard’ grown under greenhouse and irrigated field conditions, along with available data from literature. We will outline subsequent work that links root system architecture to storage root initiation, leading to future studies on the dynamics of carbon-related processes that determine the competency of adventitious roots to become storage roots.

Plastic pollution is an emerging concern for both aquatic and terrestrial ecosystems. Recent studies, primarily focused on cereals and vegetable crops, have demonstrated that nanoplastics (NPs) can enter root tissues and translocate throughout the plant. However, the accumulation and impact of NPs in woody perennial crops, particularly citrus, remain largely unexplored. This study investigated the effects of green, fluorescent polystyrene nanoplastics (PS-NPs) of two particle sizes (20 nm and 50 nm diameter) on citrus root development, nutrient uptake, and root anatomical features. ‘US-942’ citrus rootstock plants were grown under sterile aeroponic conditions and treated with PS-NPs for 15 and 30 days. Root system architecture traits, including total root length, surface area, and number of forks, were analyzed using WinRHIZO™ software. Concurrently, macronutrient and micronutrient concentrations (N, P, K, Mg, S, B, Fe, Cu, Mn) were assessed in plant tissues, and root anatomy was examined using fluorescence and light microscopy. Exposure to 20 nm PS-NPs significantly reduced total root length (–28%), surface area (–31%), and the number of root forks (–35%) at both timepoints compared to controls. Nutrient uptake was also adversely affected, with notable reductions in N, P, K, Mg, and several micronutrients. Microscopic analyses revealed that both PS-NP sizes were retained at the root surface, with no evidence of internalization or translocation into root tissues. However, alterations in epidermal and cortical cell layers suggested structural stress responses, despite the development of intact apoplastic barriers near root tips. These findings highlight the potential phytotoxic effects of PS-NPs on citrus, particularly at smaller particle sizes, and suggest that while internal uptake may be limited in woody perennials, surface-level interactions may disrupt root development and function. This study contributes to a growing understanding of nanoplastic interactions in horticultural tree crops and raises important questions regarding long-term impacts on soil-plant systems.

The plant root system is vital for nutrient uptake and plays a significant role in abiotic stress adaptation and defense. In sweetpotato, optimum root system architecture (RSA) development determines storage root (SR) yield potential. Root architectural responses to simulated natural lead levels (Pb) during the establishment and SR formation phases were characterized in two sweetpotato cultivars with known contrasting storage root yield potentials. Cultivars ‘Bayou Belle’ (BB) and ‘Beauregard’ (BX) grown on sand substrate were provided with 0.5X Hoagland’s nutrient solution with varying levels of Pb: 0, 10, 20, and 30 mg⋅L-1. The first experiment sampled entire root systems at 5, 10, and 15 days, corresponding to key adventitious and SR development stages. The cultivars varied in RSA attributes in response to Pb levels. In contrast to the cultivar BB, BX provided with 10 mg⋅L-1 Pb showed 83%, 21%, and 15% increases in main root length relative to the untreated controls at 5, 10, and 15 days, respectively. The cultivar BB consistently showed increased lateral root number and length relative to BX across all treatment levels. A second experiment was performed to produce SR samples at 50 days. The cultivar BX accumulated a 200- and 300-fold increase in Pb in SR at 20 and 30 mg⋅L-1 Pb, respectively, relative to BB storage roots at similar Pb levels. There were no differences in Pb accumulation across treatment levels in the cultivar BB. These findings are consistent with the hypothesis that increased root mass was associated with low accumulation of Pb and provide a basis for incorporating RSA traits in selecting Pb-tolerant cultivars.

Cowpea is an excellent crop for growers with small-to-medium farms and marginal lands prevalent throughout the southeast, but a thorough understanding of its response and tolerance to aluminum toxicity is lacking. This study characterized the transcriptome of two cowpea varieties, the tolerant Mississippi Pinkeye 2 Purple Hull (MSP2PH) and sensitive White Acre (WA), using RNA sequencing 6, 24, and 48 hours after treatment with 50µM AlCl3. RNA integrity number (RIN) scores of all samples were above 9.0 indicating high-quality, and the total number of reads from each sample ranged from about 20,000,000 – 60,000,000. Sample groups clustered by variety, treatment, and time point after principal component analysis. A threshold of 1 log-fold change (logFC) and a false-positive discovery rate of p ≤ 0.01 was used to identify differentially expressed genes (DEGs) for all comparisons. The number of DEGs between plants of the same variety under control and aluminum-toxic conditions at 6, 24, and 48 hours after treatment were 308, 385, and 173 for MSP2PH and 935, 1029, and 1208 for WA. 12 and 58 of these DEGs were detected across all three time points for MSP2PH and WA, respectively. Among DEGs between MSP2PH and WA that were unique under aluminum treatment there were 401, 613, and 623 at 6, 24, and 48 hours, respectively, with 58 across all time points. The number of common DEGs detected that were unique between MSP2PH samples under aluminum and control and those between MSP2PH and WA under aluminum only were 24, 67, and 19 after 6, 24, and 48 hours, respectively. Furthermore, three DEGs across all time points were detected using these criteria, and all were up-regulated in MSP2PH. One of these genes is annotated as a leucine-rich repeat (LRR) receptor-like kinase, which are well-known to regulators of aluminum-toxicity response and tolerance. Arabidopsis homologues for corresponding genes from different up- and down-regulated DEG sets were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment analysis. The number of enriched genes categorized into specific GO terms varied by time point, treatment, and variety. The number of transcription factors up- and down-regulated from specific transcription factor families were also evaluated for select comparisons and showed similar variability. These findings provide insights into expression pathways involved in aluminum toxicity tolerance and response while providing candidate genes that may be used to develop aluminum-tolerant cultivars.