If you've not yet seen the Wet Wilts video above, give it a looksie! I simplified the role of the Casparian strip in the video, the deeper science is even more exciting!
The information below was sourced from Plant Physiology (Fifth Edition) by Lincoln Taiz and Eduardo Zeiger.
Before the Casparian strip, water enters a plant through three pathways:
- Symplast and transmembrane pathway: Moving through a network of interconnected cells.
- Apoplast pathway: Moving through the space between cells.
- Transmembrane pathway: Moving in and out of cells.
Before entering the core of a plant (endodermis), all water must move to the symplastic pathway. To enter this pathway, water (and solutes) must pass through the plasma membrane of a cell. Water movement across plasma membranes is dependent on aquaporins. Aquaporins are proteins in a cell's membrane that serve as channels for water transport. The permeability of aquaporins is influenced by several factors including temperature, anaerobic conditions, and pH. 'Wet Wilts' as described in the video occur because of anaerobic conditions. The reduced respiration rates in response to anaerobic conditions “can lead to increases in intracellular pH. This increase in cytoplasmic pH alters the conductance of aquaporins in root cells, resulting in roots that are markedly less permeable to water. The fact that aquaporins can be gated in response to pH provides a mechanism by which roots can actively alter their permeability to water in response to their local environment.” Wow science is awesome. To sum it up:
- Low oxygen environment leads to reduced respiration in root zone
- Reduced respiration leads to increased cytoplasmic pH
- Higher cytoplasmic pH leads to reduced permeability in aquaporins
- Reduced permeability in aquaporins leads to 'wet wilt'
When will you see wet wilt?
- High light levels: full sun or powerful grow lights increase transpiration and water uptake demand
- Poor drainage: leads to low oxygen levels in root zone reducing permeability of aquaporins
- Low humidity: increases transpiration thus increasing water uptake demand
- Large plants: large plants often transpire more than small plants, increasing uptake demand
Products used in this video
My partnership with Hydrofarm does not force me to show specific products, I only choose my favorites to feature. Here are the products I used in this video: