Totally Potent!

or, How I Learned to Stop Worrying and Let Plants Do Their Thing

Russell Mertel

One of our super plants in the PNW! - Sitka Willow

I have been fascinated by the vitality and adaptability of plants since I was a young child, when my parents set aside a 4-square-foot plot for me to grow radishes and learn about gardening. I’ll spare you any painful puns of seeds being planted or a passion taking root, but I’ll say I can easily recall, decades later, how fresh and delicious was the sandwich my mom made from the spoils! Since then, and over the years, propagation, cloning, grafting, mutualism, decomposition, and nutrient cycling have become special horticultural interests for me. I am thrilled to share a moderately deeper examination of a foundational mechanism of plant growth – totipotency – and how it influences the use of plants in conservation and restoration, as well as how it can complicate these objectives when it occurs in undesirable plants.

What is Totipotency?

Put simply, totipotency describes the capacity of a single cell to divide and differentiate into specialized cells. Totipotency is not unique to plants (think of stem cells in animals!) but is utilized by them in remarkable, novel ways.

Totipotency in Plants

Plant cell totipotency was proposed by botanist Gottlieb Haberlandt in 1902. Haberlandt’s hypothesis was that entire plants could be cultivated from individual somatic cells – which is to say, all of the cells which make up the body of an organism with exception to reproductive cells. Recall how totipotent animal cells tend only to occur in early development with undifferentiated cells. In plants, cells that have already differentiated (e.g. into roots, stems, leaves, etc.) are able to produce cells of other types. Subsequent experiments have supported Haberlandt’s hypothesis. Picture a leaf cutting of an aloe vera, which has been transplanted and eventually grows new roots! By contrast, an animal’s teeth could not grow new gums. In reality, not all plant cells are totipotent, and oftentimes, the totipotency of somatic plant cells is only expressed under specific conditions (i.e. with the assistance of rooting hormones, nutrients, ideal soil conditions, etc.)

Totipotency in the Field

The ability of plants to clone themselves from discrete pieces is both incredibly useful, and severely problematic. The totipotency of willow cells, as well as their preferred habitat and growth habit, make it ideal in stream restoration in its native range, where relatively small pieces taken from a single willow tree can be planted in the ground with minimal pretreatment and produce entire trees which provide shade to the stream and support the cultivation of other native plants. The presence of indolebutyric acid in willow is also useful in encouraging totipotency in the cells of other plants, making it a valuable horticultural resource. Conversely, totipotency in invasive plants can present challenges to conservation and restoration efforts. For instance, almost all Japanese knotweed in North America, considered one of the world’s worst invasives outside of its native range of Japan, was cloned from a single genotype by vegetative fragmentation – chunks of knotweed broke off and grew clones; it is now present in much of North America, including 42 states of the USA as well as 8 Canadian provinces

Nitty Griddy - Totipotency vs. Pluripotency

Getting more into the science! totipotent cells within an organism can differentiate into any type of cell found in a mature individual. In animals, totipotent cells are found in early development, and eventually differentiate into pluripotent cells which then go on to differentiate into multipotent cells, and finally, specialized tissues like muscular tissue and neurons (among others!) Notably, totipotent cells in animals tend to be undifferentiated, reproductive cells.

Sources

Biology Online. (2022, June 16). Totipotent. Biology Articles, Tutorials & Dictionary Online. https://www.biologyonline.com/dictionary/totipotent

Su, Y., Tang, L., Zhao, X., & Zhang, X. S. (2020). Plant cell totipotency: Insights into cellular reprogramming. Journal of Integrative Plant Biology, 63(1), 228–243. https://doi.org/10.1111/jipb.12972

Kumar, S. (2015, October 26). Totipotency: Meaning, Expression and Importance | Plant Tissue Culture. Biology Discussion. https://www.biologydiscussion.com/plant-tissues/totipotency/totipotencymeaning-expression-and-importance-plant-tissue-culture/14641

Grevstad, F.S., R.L. Winston, R.S. Bourchier, R. Shaw, J.E. Andreas, and C.B. Randall. 2018. Biology and Biological Control of Knotweeds. USDA Forest Service, Forest Health Assessment and Applied Sciences Team, Morgantown, West Virginia. FHTET-2017-03.