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Are Greenhouse Gases Making More Powerful Herbs?

Our planet is remarkably resilient. Planet Earth has built in feedback systems that allow it, within reason to heal itself and maintain the global climate in the optimal zone to support life.

Greenhouse gasses are a case in point. When CO2 levels rise, plant life flourishes. The increased plant biomass, through the process of photosynthesis, converts the CO2 to oxygen. Oxygen levels rise CO2 levels are brought back to normal. This “Carbon Cycle” maintains the earth over millennia in a remarkable stable zone.

Most scientists agree that we are currently in a period of rising CO2. While rising CO2 levels will have many negative consequences for human life, what about plants? Is it possible that rising CO2 levels are actually a boon to plants? Will plants grow stronger over the coming decades?

There has been a lot of research on global warming as a whole. There is remarkably little research into the effect global warming is having on plants.

A fascinating study crossed my desk this week. Scientists looked at the effect of rising CO2 on the medicinal herb Jiaogulan (aka Gynostemma pentaphyllum). Higher CO2 levels and the expected accompanying higher temperatures do indeed turn out to be a boon to plants.

The jiaogulan grown in higher CO2 levels and higher temperatures grew faster and larger. The dry biomass, that is the weight of the jiaogulan after drying, was “significantly” higher. The high CO2 plants were also higher in sugar and in one type of gypenoside (Gypenosides-A).

However, the high CO2 jiaogulan was lower in total antioxidant capacity and lower in total phenol and flavonoids. This means, in short, that while there was more jiaogulan it was less potent and less flavorful.

 Interestingly, this bears out our own experience with seasonal variations in jiaogulan quality. Because jiaogulan is grown in tropical and semi-tropical climates and we harvest the leaves themselves not the fruit (yes, jiaogulan does produce a small inedible fruit), we can harvest jiaogulan year ‘round. But, we (and you) can discern the difference. The Winter/Spring harvests tends to be smaller leaved and more flavorful, whereas, the Summer/Fall harvests tends to be larger leaved but less flavorful.