The Physiology of Cannabis: A Webinar in Review

Led by Jim Pryor and Matthew Dent from Can-Hub, this webinar gives viewers an overview on the fundamentals of cannabis physiology presented by Current’s senior plant scientist, Hans Spalholz, Ph.D.

During the webinar, Hans covers several topics related to the basics of cannabis. You can view the full presentation on demand and read on for a summary of the main points.



1. What is cannabis? The biology, the product, and the taxonomy.
Hans discusses how the taxonomy of cannabis can be viewed from three perspectives: genetics, functionality, and chemotyping.

Genetics are the building blocks of cannabis and are always evolving, while the growing environment is the structure that is built on top of those genetic foundations. With chemotyping, a combination of genetics and environmental influences lead to different chemical profiles, which are the internal elements that you can taste and smell within a cannabis plant. Hans emphasizes that cannabis is not all genetically uniform, as variations are very common. As a result, evolution often tells growers how to manage their crops.

2. How biology influences the management of the crops in terms of the different grow stages and strategies for those stages.
Hans outlines the three main functionality types of plant taxonomy, which include: fiber, seed, and cannabinoid/medicinal cannabis. Along with discussing the characteristics of each type, Hans defines photobiology and how understanding the photoperiod of each grower can lead to a better understanding of their lighting regiment needs in their growing operations.

A point of emphasis for Hans is that seed exclusion and pollination prevention is critical to maintaining top plant quality in cannabis operations. Hans also explains how there is such a thing as a cannabis plant that is too healthy. He reveals how to maintain a balancing act with light by pushing the plant to root as fast as possible, without stressing the plant with too much light.

3. What marks and influences cannabis quality?
Hans explains what to focus on and look for during each stage of the plant growth cycle, concluding that the last two weeks of the growing cycle are the most important to ensuring a successful harvest. He also goes into detail about what makes a quality crop in cannabis. Hans puts a large emphasis on flower quality as a good indication of overall plant quality. He explains how other elements such as color concentration, size of bud, and history/level of sanitation within a cannabis operation can either increase or decrease the quality of a cannabis plant.

Top Viewer Questions
Hans wrapped up the webinar by taking viewer questions. Here are the inquiries that got the most interest.

Q: In different growing systems, can a plant in flowering go to a vegetative state if there is a spell of warm weather?
A: For the most part, no. Warm weather may decrease flower quality, but biologically the plant cannot revert back to a vegetative state. In some instances, it has been shown that plants can be manipulated back into a vegetative state, but the amount of resources and energy needed to do so doesn’t make it viable for commercial growers.

Q: Do you think breeders are moving more toward tissue culture in an attempt to get that uniformity and retain some of the genetics within cannabis?
A: Yes, tissue culture has its role to play, especially during the early stages of cultivar development. An extra tissue culture is used when they’re trying to introduce new genetics that are pure and clean. It’s an extra measure of sanitation and security to ensure that you are getting good, quality material into your greenhouse. It is, however, somewhat cost prohibitive.

Q: Are there any visible triggers that would give a grower an indication of when they need to push their plants into the vegetative stage, or is it based on grower experience with that crop?
A: A little bit of both. Experienced growers will always be checking root development, as that is their largest indicator. Each grower will have their own metric and threshold for that. It is looking at the roots that’s important.

If you’re interested in learning more about growing cannabis, register for the second part in this webinar series, “Uncovering the Right Light Quality & Quantity for Your Cannabis Crop.”