Plant Cuttings

Plants famously are generally immobile, fixed to one spot on the planet (Jean-François Briat). But, that doesn’t mean that they have no capacity to cover more surface area. Using structures such as above-ground runners (Margaret Quisenberry) and stolons an individual plant can extend its reach far beyond that of the original plant. And, if a new plant develops and roots where the runners contact the ground, one plant can establish a large colony of genetically-identical individuals. I.e. it will have ‘moved’ to cover a larger area. But, such movements – under the plant’s own steam – tend to be rather small-scale, over distances of a few dozen metres. To cover greater distances, plants require a bit of assistance, and a suitably-protected structure designed for long-distance transport. In the case of flowering plants, that structure is the seed (Hans Lambers); the assistance can be non-biological – e.g. water or wind (Melissa Petruzzello) – or biological, e.g. bats (Nancy Simmons et al.) or birds (Alice Moon).

Technically, the phenomenon of seeds being transported away from the parent plant is known as ‘chory’. And that is used as the suffix to describe the agent responsible for the transportation, e.g. hydrochory is transportation by water, and anemochory is where wind or air currents are employed. Zoochory (Michelle Ross]) is the umbrella term for a whole range of transportation types using animals. Broadly-speaking, where animals are concerned, seed carriage can be via the outside of the organism – epizoochory, or within the creature – endozoochory (Anna Traveset et al.).

For endozoochory to complete the job, the internalised seed needs to be expelled from the animal’s body. That externalisation is usually along with faeces. In which case, not only has the seed been transported away from the parent – with which established plant it might compete – poorly – for resources to establish itself as a separate individual – but is also deposited amidst plant-nourishing nutrients within the pile of ‘poo’, or ‘manure’.

Combining the human fascination with record-breaking feats by members of the animal kingdom (e.g. Matthew Wilson, Sarah McPherson, Petr H, and Jed Winer, and extending the range of organisms involved in zoochory, is work by Kenji Suetsugu et al. ((2024), Plants, People, Planet* https://doi.org/10.1002/ppp3.10519). Investigating the capacity of invertebrates (Blake Scarborough) to disperse seeds of Monotropastrum humile (a non-photosynthetic, mycoheterotrophic (Vincent Merckx et al., Ann Bot. 104(7): 1255–1261, 2009; doi: 10.1093/aob/mcp235) plant with dust-like seeds).

The researchers found that seeds were consumed principally by the camel cricket (Diestrammena brunneri), the woodlouse (Porcellio scaber), and the earwig (Anechura harmandi). Which can be fine, consumption is not necessarily the same as digesting the seeds and absorbing the breakdown products. Except, in the case of the woodlice and earwigs which “were more inclined toward seed predation”, as opposed to the crickets. However, although Suetsugu et al. note that the crickets were the main seed-dispersers, they did record instances where some seeds defecated by earwigs and woodlice not only remained intact, but were also viable. Suetsugu et al. (2024) therefore concluded that earwigs and woodlice “could also function as dispersal agents”. Furthermore, the small size of P. scaber (8–11 mm in length and 5 mm in width) “establishes a new record as the world’s smallest internal seed dispersal agent”**, and, A. harmandi is potentially “the lightest endozoochorous seed disperser known”*** . One wonders – not-unnaturally – if even smaller seed-dispersing organisms await discovery. However, that would probably be dependent upon finding seeds that are even smaller than the ‘dust-like’ ones of Monotropastrum humile…

* As interesting as this discovery is, it may not be immediately obvious why this work appears in Plants People Planet, a journal whose vision is: “to promote outstanding plant-based research in its broadest sense and to celebrate everything new, innovative and exciting in plant sciences that is relevant to society and people’s daily lives”. However, if you look at the journal’s stated Aims and Scope you find that one of the six broad themes in which it publishes is Plant Natural Assets, which includes: “Plants, human health and wellbeing; Crops and agro-ecology; Ethnomedicine and drug discovery; Phylogenetics of medical plants; Natural asset sharing policy (Nagoya); Plants and food security; Plant-insect interactions and ecosystem services; Environmental economics”. The penultimate category in that listing is presumably where Kenji Suetsugu et al’s paper fits. Although, it could also relate to the Plant Diversity theme, which covers “Coevolution and mutualisms”. In any event, Kenji Suetsugu et al. (2024)‘s paper seems to fit within the stated remit of Plants People Planet.

** If, like me, you were thinking “Hang on a minute, what about ants? Some of them are quite a bit smaller than woodlice (Ashley Smith), and also disperse seeds [myrmecochory]”. Then, yes, they are, and do. But, as far as I know, they don’t ingest seeds and then disperse them, which is the woodlouse ‘claim to fame’.

*** For more scicomm items about this investigation, see here, here, and Gennaro Tomma.