The O 2 budget of seagrasses is regulated by a complex interaction between several sources and sinks, which is strongly regulated by light availability and mass transfer over the diffusive boundary layer (DBL) surrounding the plant. Epiphyte growth on leaves may thus strongly affect the O 2 availability of the seagrass plant and its capability to aerate its rhizosphere as a defense against plant toxins. We used electrochemical and fiber-optic microsensors to quantify the O 2 flux, DBL, and light microclimate around leaves with and without filamentous algal epiphytes. We also quantified the below-ground radial O 2 loss (ROL) from roots (∼1 mm from the root-apex) to elucidate how this below-ground oxic microzone was affected by the presence of epiphytes. Epiphyte-cover on seagrass leaves (∼21% areal cover) resulted in reduced light quality and quantity for photosynthesis, thus leading to reduced plant fitness. A ∼4 times thicker DBL around leaves with epiphyte-cover impeded gas (and nutrient) exchange with the surrounding water-column and thus the amount of O 2 passively diffusing down to the below-ground tissue through the aerenchyma in darkness. During light exposure of the leaves, radial oxygen loss from the below-ground tissue was ∼2 times higher from plants without epiphyte-cover. In contrast, no O 2 was detectable at the surface of the root-cap tissue of plants with epiphyte-cover during darkness, leaving the plants more susceptible to sulfide intrusion. Epiphyte growth on seagrass leaves thus has a negative effect on the light climate during daytime and O 2 supply in darkness, hampering the plants performance and thereby reducing the oxidation capability of its below-ground tissue.

For decades, significant effort has been put into the development of plant detection and classification algorithms. However, it has been difficult to compare the performance of the different algorithms, due to the lack of a common testbed, such as a public available annotated reference dataset. In this paper, we present the Open Plant Phenotype Database (OPPD), a public dataset for plant detection and plant classification. The dataset contains 7590 RGB images of 47 plant species. Each species is cultivated under three different growth conditions, to provide a high degree of diversity in terms of visual appearance. The images are collected at the semifield area at Aarhus University, Research Centre Flakkebjerg, Denmark, using a customized data acquisition platform that provides well-illuminated images with a ground resolution of ∼6.6 px mm − 1 . All images are annotated with plant species using the EPPO encoding system, bounding box annotations for detection and extraction of individual plants, applied growth conditions and time passed since seeding. Additionally, the individual plants have been tracked temporally and given unique IDs. The dataset is accompanied by two experiments for: (1) plant instance detection and (2) plant species classification. The experiments introduce evaluation metrics and methods for the two tasks and provide baselines for future work on the data.

Most lumbricid earthworms harbor species-specific Verminephrobacter symbionts in their excretory organs (nephridia). These symbionts are vertically transmitted via the cocoon, where they colonize the embryos. Despite cospeciation for >100 million years with their hosts, Verminephrobacter lack genome reduction and AT bias typical of evolutionary old, vertically transmitted symbionts, caused by recurring bottlenecks. We hypothesized that biparental symbiont transmission into the cocoon enabled genetic mixing and relieved the bottleneck, and tested biparental transmission experimentally for V. aporrectodeae subsp. tuberculata, the specific symbiont of the earthworm Aporrectodea tuberculata, for which aposymbiotic worm lines are available. Virgin symbiotic and aposymbiotic adult worms were tagged, mated in pairs, separated before the start of cocoon production and their offspring assessed for Verminephrobacter. Specific PCR detected the symbionts in 41.5% of 188 juveniles produced by 20 aposymbiotic worms; fluorescence in situ hybridization showed a patchy but successful colonization of their nephridia. Symbionts were present in the mucus but absent in feed, soil, and spermatophora/nephridia of the aposymbiotic partner, suggesting symbiont transfer via mucus during mating. These results are consistent with the hypothesis that genome evolution in Verminephrobacter is distinct from other vertical-ly transmitted symbionts due to genetic mixing during transmission, partially facilitated by biparental transmission.

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