Photosynthesis - 101a

Photo credit: Marc Suderman

Photosynthesis – Everyone, everywhere benefits from plants; specifically from Photosynthesis. It’s the plant process that takes water (6H₂O), carbon dioxide (6CO₂) and sunlight (energy) and transforms them, into glucose (C₆H₁₂O₆) and oxygen (6O₂) during daylight hours. This supplies food for plants and oxygen (and food) for the rest of us. It is the most vitally important activity on earth.

Approximately 95% of all plant structures are made up of carbon, hydrogen, oxygen…95%! These are taken from the air via the photosynthetic process. While this is a plant activity, it is dependent upon a living, nutrient-rich soil for supplying water and the necessary mineral nutrition, which cannot be gotten from the air. The mineral nutrition is the part where we have a direct effect; the 5%. To make this dynamic system work well requires “give-and-take” action. There’s a symbiotic relationship between plants and soil (biology). Plants need what only the microbes can provide and are unable to get for themselves and vice versa. Plants make sugars and soil microbes eat sugars. Soil microbes liberate soil-bound minerals that plants cannot release, but need for survival; interdependence. Of the sugars produced, plants use ⅓ of these photosynthates within the canopy and the remaining ⅔ are sent down into the root system. This is a win-win arrangement. The more diverse and active the rhizosphere (the area surrounding plant roots where microbes live), the more the food demand will be, but this also means there is more reproduction too. This will improve nutrient translocation for better plant health and therefore higher glucose production for better rootzone health. This creates, in effect, a perpetuating action between soil and plant.

Plants are made to be in the sun. They are designed to absorb sunlight and the heat that comes with it. Summer brings plenty of sunlight and higher temperatures. A healthy canopy should provide food and protection to the developing crop, but sometimes there are limitations to the canopy’s effectiveness. These can be a challenge at critical stages of development and can cause problems for growers. A good understanding of the key growth stages for your crop is important. This can help you better plan for potential stressors, like weather, drought, bloom, fruit set, fruit fill, etc. Designing a fertility plan for the nutrient demands of growing crops (before they need them) and emphasizing key nutrients, like phosphate, magnesium, iron, boron, manganese, etc. to lessen plant stressors and promote better plant/soil health via the photosynthetic process, is in your best interest. Dan Skow wrote, in Mainline Farming for Century 21, “In photosynthesis there is one limiting factor, in putting sugars into plants, namely phosphate...” For instance, excessive light and heat can cause plant stress. The Stress is not the problem, but a symptom of the Problem, namely nutrient deficiency. Considering every nutrient, with the exception of nitrogen, enters the plant in phosphate form, shows how key a nutrient this is to overall plant health and function. In calcareous soils, this is a challenge. Adding specialized soil microbiology will provide an ample soil phosphate supply and plants respond by building larger, thicker, hardier leaves that are better suited to care for themselves. These are plants’ solar panels and the better they are equipped for “catching” sunlight, the better the sugar production. “The number of layers [in the mesophyll] varies, principally due to nutrition. More layers mean a thicker leaf, more photosynthesis, and more crop.” wrote Dr. Arden B. Andersen in Science in Agriculture. Thicker leaves have a larger storage volume and higher solute (sugars) content. As a result, this gives a plant more resistance to rising ambient temperatures and helps to regulate its internal temperature better. This also allows the guard cells of the stomata to remain open longer into the day before shutting down to conserve water. More photosynthetic production yields more energy and more energy equates to more plant health. It takes healthy plants to grow nutrient-rich food. The crop produced can be nothing more than the “nutrient-template” provided it from the diet of the parent-plant; “Garbage in, garbage out” or “You are what you eat”. Making assumptions about the soundness of your fertility plan without verifying with timely tissue testing can prove to be costly. Growing high quality fruits or vegetables doesn’t just happen. It’s a lot like trying to hit a moving target. It requires a good plan and execution to get good canopy efficiency. The opposite is also true, if anything occurs to limit a plant’s ability to absorb sunlight and build photosynthates. I mention this because; summer is a critical time for fruit bud development which happens concurrently with all other plant operations and can place added energy/nutrient demands, onto a plant. Deficiencies, at this stage, can ill-affect production for the coming year. Remember, the higher the photosynthetic efficiency, the better equipped a plant is to address all plant issues. This includes generating high quality crops and higher quality equals better ship-ability and shelf-life. But, to do this takes energy (sugars). Plants “bundle” sugars to form primary and secondary metabolites. It takes ten times more energy to produce secondary plant metabolites than glucose. Without secondary metabolites, strong, high quality, nutrient dense fruits or vegetables are not possible. This is directly dependent upon how well plants photosynthesize. Bottom line: When plant glucose production fails to meet plant demands, crop quality suffers. Don’t let this happen to you!

 

 

Photosynthesis, on the surface, can be assumed to be nothing more than the plant activity of absorbing sunshine and growing. But, it is a very complex process; one that works for you, but can be limited or benefitted by your fertility plan, both in the soil and the plant. Nutrition has a major influence on crop yield, plant health and soil response. Fertilizing a crop, with good intentions doesn’t guarantee good results. Regular and timely tissue and soil testing are useful tools for tracking your growing progress. Fertilizers and lab testing cost you money, but so does delivering a crop that has sub-par quality, size, color, brix, firmness, etc. on your bottom line. Utilizing test results to make timely nutrient decisions is good stewardship. Good stewardship is also making sure your plant’s canopy is functioning at a high level of efficiency to support your efforts to produce the best crop possible each and every year.

Here’s to your harvest success!