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Hydrolife Magazine February/March 2017 (USA Edition)

It is amazing how an event from almost 20 years ago can remain fresh in the mind. It certainly doesn’t seem that long ago that Canadian Ross Rebagliati rocketed down Nagano’s Olympic giant slalom snowboard course, ripping through the finish line to claim the first-ever Olympic men’s snowboarding gold medal despite starting the final run in eighth position. Since then, Rebagliati has become a cultural phenomenon and advocate of marijuana use, and it is no coincidence that since that foggy day on Mount Yakebitai near Nagano, how we perceive the use of marijuana in society has changed for the better. Hydrolife recently caught up with Rebagliati to talk about Nagano, his thoughts on marijuana, and the launch of Ross’ Gold.

grow loss through

grow loss through transpiration. Leaves close stomata to reduce water loss, but doing so reduces CO 2 uptake. It's a dry world out there, and C3 plants constantly regulate stomatal openings to balance CO 2 uptake against water loss. Due to the large moisture gradient between leaves and the surrounding air, taking in CO 2 is costly in terms of water. Dr. Suman Chandra, lead author in several federally sanctioned studies on cannabis physiology, found that when CO 2 concentrations are raised well above ambient, cannabis responds by partially closing its stomata. Without the need for CO 2 driving them to open, the stomata naturally close to conserve water. This is important for several reasons. It means that cannabis water use, per unit area, may decrease with CO 2 fertilization. It also makes air mixing even more important, since partially closed stomata will slow CO 2 uptake. Finally, this can lead to higher leaf temperatures by restricting transpiration. TEMPERATURE AND LIGHT INTENSITY CO 2 fertilization allows cannabis to thrive at higher temperatures and utilize higher light intensities, but these two factors need to be considered together. Light comes with more heat, especially in HID illuminated environments. Both parameters shift the photosynthetic machinery into higher gear and CO 2 enrichment allows it to run faster and cleaner. However, even with CO 2, pushing too hard with light and/or temperature can send your plants into stressful conditions. The general recommendation for maximizing CO 2 fertilization in greenhouse crops is to raise the growth temperature by five to 10 degrees Fahrenheit above the ideal temperature in the absence of CO 2 enrichment. For cannabis, this means that the ideal bloom temperature is shifted into the mid to high 80s. It is important to note that ambient grow temperature does not usually represent the temperature that the plant canopy is experiencing. A room temperature in the low 80s will translate to canopy temperatures closer to the ideal for growth with CO 2 enhancement. Some strains may enjoy an even higher temperature, but I don't recommend running your space above 83oF unless you know your strains will respond favorably and you have tight control of other environmental parameters. Be cautious when pushing the temperature envelope, the difference between ideal and harmful can be a few degrees. IDEAL CO 2 LEVELS One of the most hotly debated aspects of CO 2 fertilization in cannabis cultivation is the proper concentration of CO 2. The only cannabis-specific research done is this area is presented in Dr. Chandra's publications. He found that raising CO 2 concentration to 700 ppm resulted in an instantaneous increase in photosynthetic productivity of 38-48 per cent, depending on strain. Unfortunately, his work doesn't discuss the effects of CO 2 fertilization at concentrations higher than 750 ppm. As CO 2 concentrations are increased well above ambient, the law of diminishing returns applies to the benefits. This means that the degree to which additional CO 2 increases productivity drops as ppms increase, ultimately reaching the point at which plant stress occurs. As with most things, too much CO 2 can have negative effects, leading to lower yields and leaf death at extremely high levels. The concentration at which CO 2 becomes detrimental to plant health varies widely between species. Tomatoes, for example, have an upper threshold of about 2,000 ppm, while chrysanthemums experience stress at concentrations greater than 1,200 ppm. In the absence of research to clarify the issue, “CO 2 FERTILIZATION ALLOWS cannabis to thrive at higher temperatures and utilize higher light intensities, but these two factors need to be considered together.” 42 grow. heal. live. enjoy. myhydrolife.com

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