Many plants developed unique adaptations such as protective seed coatings or eatable fruits/seeds that aid in seed dispersal by animals. Birds are among the animals that perform endozoochoric diaspore dispersal. In this study, we used mechanically demucilaginated seeds and seeds covered with artificial mucilage with the aim of determining the protective potential of the mucilage envelope against seed digestion during endozoochory by birds. We removed the mucilage from the seeds of Plantago lanceolata, Plantago ovata, Plantago psyllium, and Linum usitatissimum and fed the seeds to pigeons. Using naturally non-mucilaginous seeds of Amaranthus albus, Brassica napus and Nigella sativa, we tested the survival of diaspores covered with artificial mucilage (P. ovata husk) in the digestive systems of pigeons. Among the demucilaginated diaspores (2700 per taxon), no seeds of L. usitatissimum, 1 seed of P. lanceolata, 1 seed of P. ovata and 7 seeds of P. psyllium passed through the bird gut intact. This indicated that after removing the mucilage envelope, few diaspores can pass through the digestive system. Among diaspores with artificial mucilage, 7 seeds (from 8100 total) passed through the bird gut intact. This indicated that the artificial mucilage did not support the survival of the seeds as they passed through the pigeon digestive system. Furthermore, germination experiments revealed a decrease in the germination rate of demucilaginated seeds. They moulded rapidly, and only a few of the seeds germinated. The results of this study demonstrate the significant role of the mucilage in preventing digestion and supporting diaspore germination during endozoochory.

With the help of instrumented indentation, the mechanical behavior of a variety of biological systems was studied: the waxy zone of the pitcher plant (Nephenthes alata) adapted for attachment prevention, the head-to-thorax articulation system of a beetle (Pachnoda marginata) as an example of friction minimization, and the wing arresting system of the dung beetle (Geotrupes stercorarius) adapted for mechanical interlocking. We demonstrate that nanoindentation can successfully be applied to compliant and highly structured biological composite materials. Measuring the mechanical performance of these surfaces can provide important information for understanding the overall functioning of these systems. Tests on fresh and dried samples show the influence of desiccation on the results and point out the importance of native conditions during the measurements. However, these preliminary results also point to current limits of the test method and the need for adapting it and current theories to meet the specific requirements of biological materials.