We know it is possible to increase the quantity of sugars produced in each 24 hour photoperiod as much as three to four times higher than the baseline of what is considered ‘normal’ or common in most crops today. In addition, it is also possible to increase the ‘quality’ or the complexity of carbohydrates produced in each photoperiod. Plants with limited nutritional integrity produce lower volumes of simple sugars. Healthy plants produce much larger volumes of more complex sugars.
When the plant begins producing larger volumes of more complex sugars, the crop begins behaving differently. There isn’t a good way to describe this. Internode lengths become shorter, while growth is faster. Clusters of fruit or heads of grain have more kernels or fruit, and mature earlier. Very importantly, the crop begins contributing more carbon to the soil than it removes, even when 100% of the above ground biomass is removed.
Here are some thoughts Don Huber shared when I asked him about photosynthesis during our first podcast interview.
John: Don, one of the things I believe is quite important that we haven’t spoken about is the general impact of photosynthesis and the quality of photosynthesis—how photosynthesis can vary in crops and cover crops and how that influences the volume of root exudates. How can a grower increase the quantity of photosynthesis and increase the quantity of root exudates in the soil profile?
Don: You’re not going to have any photosynthesis if you don’t have manganese. Manganese is critical for splitting water; it provides the hydrogen that can then combine with carbon dioxide. You’re not going to have any photosynthesis without magnesium, which is part of the chlorophyll molecule. You’re not going to have a very efficient photosynthesis without iron and sulfur and all the other minerals, because your physiology is all tied together.
If you want to improve the efficiency of photosynthesis, the first place to look is mineral availability—having that system work. So, if you don’t have a backlog of sugar as fructose or glucose, you want that sugar to be stored as sucrose. That changes the osmotic relationship; it changes the overall physiology of the plant. You’re also not going to have any sucrose if you don’t have manganese, because manganese is responsible for your sucrose-phosphate synthase enzyme as a cofactor.
It’s a system that works together. If you don’t have sulfur, you won’t have enzymes, because most of your proteins are initiated with either cysteine or methionine—your sulfur amino acid. C4 plants have a more efficient photosynthetic pathway. They have PEP carboxylase, as well as rubisco enzymes—after the carbon dioxide from the air binds with the hydrogen that is split off of the water by manganese. So, you have C4 plants and C3 plants, and the physiology that’s involved—but all of them require the mineral nutrients. And any one of those deficiencies influences the overall efficiency of the whole process.