Rowland, D. | bioRxiv Science

bioRxiv2021

Spatial and Texture Analysis of Root System Architecture with Earth Mover's Distance

PurposeRoot system architectures are complex and challenging to characterize effectively for agronomic and ecological discovery. MethodsWe propose a new method, Spatial and Texture Analysis of Root SystEm distribution with Earth movers Distance (STARSEED), for comparing root system distributions that incorporates spatial information through a novel application of the Earth Movers Distance (EMD). ResultsWe illustrate that the approach captures the response of sesame root systems for different genotypes and soil moisture levels. STARSEED provides quantitative and visual insights into changes that occur in root architectures across experimental treatments. ConclusionSTARSEED can be generalized to other plants and provides insight into root system architecture development and response to varying growth conditions not captured by existing root architecture metrics and models. The code and data for our experiments are publicly available: https://github.com/GatorSense/STARSEED.

plant biology↗

bioRxiv2021

Citrus photosynthesis and morphology acclimate to phloem-affecting huanglongbing disease at the leaf and shoot levels

Huanglongbing (HLB) is a phloem-affecting disease of citrus that reduces growth and has impacted global citrus production. HLB is caused by a phloem-limited bacterium (Candidatus Liberibacter asiaticus; CLas). By inhibiting phloem function, HLB stunts sink growth, including reducing production of new shoots and leaves, and induces hyperaccumulation of foliar starch. HLB induces feedback inhibition of photosynthesis by reducing foliar carbohydrate export. In this work we assessed the relationship of bacterial distribution within the foliage, foliar starch accumulation, and net CO2 assimilation (Anet). Because HLB impacts canopy morphology, we developed a chamber to measure whole-shoot Anet to test the effects of HLB at both leaf and shoot levels. Whole-shoot-level Anet saturated at high irradiance, and green stems had high photosynthetic rates compared to leaves. Starch accumulation was correlated with bacterial population, and starch was negatively correlated with Anet at the leaf level but not at the shoot level. Starch increased initially after infection, then decreased progressively with increasing length of infection. HLB infection reduced Anet at the leaf level, but increased it at the whole shoot level, in association with reduced leaf size and greater relative contribution of stems to photosynthetic surface area. Although HLB-increased photosynthetic efficiency, total carbon fixed per shoot decreased because photosynthetic surface area was reduced. We conclude that the localized effects of infection on photosynthesis are mitigated by whole shoot morphological acclimation over time. Stems contribute important proportions of whole shoot Anet, and these contributions are likely increased by the morphological acclimation induced by HLB.

plant biology↗