Just Add Water–The Nodes Know

Author

Mpule Clarke

Published

July 23, 2024

Just Add Water–The Nodes Know

An overview of the involvement of nodes in Mentha L. sp propagation

                                            



Figure 1. Mentha L. sp. (Mint)


Mint (Mentha L. sp.) classification (USDA Plants database, n.d):

Kingdom: Plantae- Plant

Subkingdom: Tracheobionta- Vascular plant

Superdivision: Spermatophyta- Seed plant

Division: Magnoliophyta- Flowering plant

Class: Magnoliopsida- Dicotyledon

Subclass: Asteridae

Order: Lamiale

Family: Lamiaceae Martinov- Mint family

Genus: Mentha L.


Mint (Mentha L.) is a flowering plant whose physiology and genetics allows it to be easily multiplied and nursed by novice gardeners (like myself). I don’t consider myself to have much of a green thumb but, this angiosperm (Prakash et al., 2016) is definitely helping my image! In this article we will explore an overview of why these little guys are so viable in water and how the molecular mechanisms of nodes in conjunction with the plant’s vegetative organs facilitate successful propagation in water.

Before getting into the workings of plant nodes we must first establish vital context and for this we will take a bird’s eye view of the plant and gradually zoom in, until we get to the molecular mechanisms as the article(s) progress. Nodes are located on the stems of most plants; stems, leaves and roots are all referred to as vegetative tissue (Rost et al., 1984). Vegetative organs of plants are the drivers of nutrition and growth; they are not responsible for reproductive processes however, they collectively prepare the plant to fulfil its reproductive cycle. 

Roots absorb water and minerals from the growth media (soil, water, agar, etc.);

Figure 2. Mint roots following propagation.

leaves facilitate photosynthetic processes;

Figure 3. Mint leaves (removed from stem for water propagation)

stems transport nutrients and water between organs as well as “sprout” new leaves and flowers;

Figure 4. Mint stems (clipped from plant for propagation)

the shoot apex is the origin of leaf formation as well as all new cells on the plant’s shoot;

Figure 5. Shoot apex of mint shoot. 

the root apex produces all new cells on the plant’s root.

Figure 6. Mint root apex. 

Now that we’ve set the macroscopic stage, we can adjust our focus to the star of this article: the node. Have you stared at a plant long enough to notice how its leaves grow on its stem? They vary by plant, however leaves are generally derived by nodal cells at variable intervals on the plant’s stem. The lengths of these intervals are not necessarily standard, but specific to the plant in question. The location where leaves protrude from the stem is called a node (Rost et al., 1984). The space between two nodes is called an internode (Rost et al., 1984).

Figure 7. Mint nodes (blue), mint internodes (red).

Nodal cells are considered to be meristematic (undifferentiated) (Buchanan et al., 2015), this indicates that some factor can influence its functionality.  In the instance of this mint propagation experiment series,  the removal of lower leaves

Figure 8. Mint stem cuttings with lower leaves removed

 and water submersion of those stems

Figure 9. Mint stem cuttings submerged in water for propagation

will trigger signals for root formation (differentiation) mechanisms at the exposed nodes. 

Figure 10. Roots grown from propagated stem nodes (Mint).

These nodal cells were influenced by the mint’s vegetative tissue, namely the leaves and shoot apex, to initiate root formation in order for successful propagation to occur. Next week we will continue our molecular investigation of Mentha L. sp. propagation; in the subsequent posts we will adjust our lenses to understand the intricate mechanics of Mint propagation in water. 



Questions to ponder until next time:

  1. What exactly are leaves?

  2. Why do they need light?

  3. Why does the light requirement vary by plant?

  4. Where does the energy harvested through light ultimately go?

Take care,

Mpule Clarke.



References

Buchanan, B. B., Gruissem, W., & Jones, R. L. (2015). Biochemistry and molecular biology of plants. John Wiley & Sons.

Prakash, O., Chandra, M., Pant, A., & Rawat, D. (2016). Mint (Mentha spicata L.) Oils. In Elsevier eBooks (pp. 561–572). https://doi.org/10.1016/b978-0-12-416641-7.00064-x

Rost, T. L., Barbour, M. G., Thornton, R. M., Weier, T. E., & Stocking, C. R. (n.d.). Botany: A brief introduction to plant biology. Wiley.

USDA Plants Database. (n.d.). https://plants.usda.gov/home/classification/45882