What follows is an extensive list of all the science factors we have taken into account in our growing systems. Please feel free to dive deep into the science of growing plants, as we do here.
Let's start with the five core things you need to grow any type of plant:
- The plant itself (the root and canopy, which, begins with the seeds),
- Nutrients, and
- Atmosphere (air, humidity, temperature).
Species, Cultivar, and Variety
Cultivar and Variety are two terms used by gardeners and horticulturists, and they are often confused. Horticulturists use the scientific designation and gardeners and farmers use the day-to-day definition. A cultivar is a general name, and the variety is a specific variation that grows true to type, meaning that a plant grown from the seed of a specific variety will be similar to other plants of the variety.
For example, there is a white flowering Redbud that was found in nature. If germinated from seed, this variety, most, if not all would also be white flowering. Another example is Basil which is the species. The cultivar is Genovese. The varieties include Italian Large Leaf, Genovese, Eleonora and many more.
Varieties are selected and cultivated by humans. Some cultivars originate as mutations on plants. Other varieties can be hybrids of two plants. To propagate true-to-type clones, many cultivars must be propagated vegetatively through cuttings, grafting, and even tissue culture. Propagation by seed may produce something different than the parent plant. Sometimes the varieties will have the same scientific name and sometimes they will be different. Different seed suppliers will name the same seed variety differently and other times they will name different seed variety the same thing.
Roots and Canopy
Plants are divided into the canopy area and the root area. Our Growing Systems provide to the canopy (a plant's leaves and stems) a) photosynthesis (turning light into vitamins), b) CO2, c) respiration, and d) storage of nutrients. Our Growing Systems help the roots acquire water, oxygen, nutrients (both Macro and Micro), storage of nutrients, and anchorage of the plant. The canopy and root areas are measured and monitored differently.
The larger the root system, the healthier the plant. Each Variety of plant will have a different ratio to shoot (shoot is a measure of canopy) to root biomass as well as a different root structures. Our Growing Systems are designed to maximize root and canopy growth, which in turn will maximize the different Cultivar Measurement Factors (described elsewhere). The Tower design addresses the needs of the root system to receive liquid, nutrients, and oxygen. The Nutrient System provides the roots the nutrients required.
Photosynthesis is the process of capturing light energy and converting it to sugar energy, in the presence of chlorophyll using carbon dioxide (CO2) and water (H2O). In Photosynthesis, carbon dioxide (CO2) from the air and water from the soil react with the sun’s energy to form photosynthates (sugars, starches, carbohydrates, and proteins) and release oxygen as a byproduct. Our custom Lighting design provides the light, Our Atmosphere system provides the CO2 and airflow, and the Nutrient System provides the liquid and the nutrients necessary for Photosynthesis to occur. The Lighting Subsystem provides the Lighting needed for Photosynthesis.
As you can see, each subsystem supports each other subsystem. Its all very cool and seems high tech. We are able to simulate the best natural grow environments do on a consistent basis without interference of weather and insects and animals.
Respiration is the process of metabolizing (burning) sugars to yield energy for growth, reproduction, and other life processes. Plants convert the sugars (photosynthates) back into energy for growth and other life processes (metabolic processes). The chemical equation for respiration shows that the photosynthates are combined with oxygen releasing energy, carbon dioxide, and water.
In the canopy, the difference in water potential in the plant versus the surrounding air evaporates water from the plants. Gas exchange (Oxygen out and CO2 in) is mediated through pores (known as stomata) located mainly on the lower side of leaves. These gases move in and out of the plant through the leaves by diffusion. When CO2 levels are low inside the plant, the guard cells gain water and become turgid (they swell). They curve out, opening the stoma and allowing gases in and out. Water also evaporates through stomata. The root subsystem is part of the respiration system with scientific estimates between one-third and two-thirds of respiration occurring through the roots.
The Tower and Atmosphere Subsystem are designed to maximize Respiration in the canopy with the Tower substrate combined with a Nutrient Formula specific to a Variety, intended to maximize Respiration for the root structures.
The Respiration Formula is Sugar + Oxygen = Carbon Dioxide + Water + Energy. Respiration generates heat. The amount of heat given off is a function of both the respiration rate of the vegetable and the current temperature. The respiration rate doubles with each 10° C (18° F) rise in temperature and so the respiration rate and the heat generated by respiration is minimized by appropriate temperature management. Respiration continues after the plant has been harvested. Post-harvest, as the respiration rate increases, the shelf life decreases. In fact, temperature is considered the single most important factor effecting shelf life in the post-harvest environment.
Liquid in the roots is pulled through the plant by transpiration (loss of liquid vapor through the stomata of the leaves). Transpiration uses about 90% of the liquid that enters the plant. The other 10% is an ingredient in photosynthesis and cell growth. Transpiration serves three essential roles:
- Movement of minerals up from the root (in the xylem) and sugars (products of photosynthesis) throughout the plant (in the phloem). Liquid serves as both the solvent and the avenue of transport.
- Cooling – 80% of the cooling is from the evaporative cooling effects of transpiration. The canopy releases water through evaporation and respiration. This respiration removes water from the plant and increases the Turgor presser.
- Turgor pressure – Liquid maintains the turgor pressure in cells much like air inflates a balloon, giving the non-woody plant parts form. Turgidity is important so the plant can remain stiff and upright and gain a competitive advantage when it comes to light. Turgidity is also important for the functioning of the guard cells, which surround the stomata and regulate water loss and carbon dioxide uptake. Turgidity is also the force that pushes roots through the soil. It's part of the “crunch” of a vegetable, an important element of texture which forms the concept of taste. In our Growing Systems, the Atmosphere Subsystem provides for the canopy respiration and transpiration needs.
In nature, water and nutrients are provided to the plants “transported” through the roots located in soil. In the current versions of our Growing Systems the soil is replaced by a grow media or Substrate to provide anchorage for the roots and presenting the nutrients to the roots. There are a number of methods which the roots use to absorb nutrients, including mass flow and diffusion. The roots absorb nutrients dissolved in a liquid, which is normally water, high levels of dissolved oxygen within the liquid increases the absorption rate. Properties of the Substrate can directly increase the quality and quantity of the nutrient transport. These properties include the liquid holding capacity, soil strength, Cation Exchange Capacity (CEC) (ion charge which represents its ability to hold nutrients), texture, compaction or density, pore space (which provide air holding capacity), and temperature. The scientific literature has suggested the greater the compaction of the Substrate, the lesser the take up of certain minerals. The internal design of the Growing Plank has a direct impact on the ability of the roots to access the nutrients contained in the Nutrient Solution.
Prolonged light will damage plant roots, and high temperature in the root zone will cause heat stress to plants, as well as fruit and flower drop as a result of heat stress. Our Growing Systems' Growing Planks are designed to limit light into the root zone while providing access to air and temperature control.
Cultivar Measurement Factors
Cultivar Measurement Factors are the all the factors together used to measure the efficacy of the plants grown in our Growing Systems. The efficacy of the current versions of our Growing Systems is measured by the health of the plants, their usability as food, and their food safety. Plant health and usability have a large interplay, and in most cases what is good for one is good for the other, but not always. The special cases are when a plant is stressed in certain ways or lacking in certain nutrients. A stressed plant will store nutrients, which represents healthy vitamins for a human being. These stored nutrients affect the taste parameters. A specific Nutritional Formula can be created to maximize or minimize the value of one or more Cultivar Measurement Factors for a specific Variety.
1) The food usability factors that are measured include Taste, Visual Appearance, Texture, Nutritional Value, Scent, and Shelf Life profiling. The primary measures for taste include the following: Bitter, Sweet, Salty, Sour , and Umami. The Taste Profile is further refined with terms like Savory, Astringency, and Tartness. Visual factors include: Color and Discolouration. Texture factors includes: Hardiness, Cohesiveness, Viscosity, Springiness, Adhesiveness, Fracturability, Chewiness, and Gumminess (Texture is a sensory property, Alina Surmacka Szczesniak - Food Quality and Preference 13 (2002) 215–225). Nutritional Value includes the USDA standard measurements such as: Proximates (water, energy, protein, etc.); i) Minerals (Calcium, Iron, etc.); Vitamins (C, A, B, etc.); Lipids (Fatty acids, cholesterol, etc.); Scent Profile includes Strong, Weak, Sour vs Sweet, and the specific scent; n) Shelf Life measures how many days the product (packaged or unpackaged) can maintain usability. Some of the specific measures for shelf life include ; o) oxidation level; and ethelyne release.
2) The factors that are measured for plant health include the following: a) BRIX level - sugar level; b) Yield amount – the weight of a plant in a particular time; c) Canopy weight: root weight ratio; d) Leaf size; e) Leaf count; f) Shoot count; g) Leaf (Canopy) biomass; and h) Shoot: root biomass ratio. 3) Food Safety factors focus on the safety of the vegetables. There a significant number of pathogens with the three most widely known by consumers being e. coli, listeria, and salmonella. The primary sources for pathogens are a) the nutrients used, b) the water used as part of the nutrient solution, c) the atmosphere and d) the people working within the environment. The primary measure for pathogens looks specifically for the pathogen, the general term used when measuring pathogens is the microbiological load.
The Nutritional Formula is a specific value of Dissolved Oxygen, Nutritional Solution, Temperature, Nutrient Formula, Atmosphere Formula, Lighting Formula, and the Nutrient Solution for a specific Variety to achieve a specific combination of Cultivar Measurement Factors.
The Cultivar Measurement Factors are primarily
- plant nutritional value,
- growing time and harvest weight.
The Nutritional Formula integrates multiple harvests of the same plant over time and is determined using a proprietary Variety Nutritional Formula technology. The Nutritional formula is continually adapted for a Variety, for the water used in a specific geographic location, and chemical analysis of the lot of the nutrients of the being used. There are multiple Nutritional Formulas for a specific Variety to address different measurements within the Cultivar Measurement Factors.
- Address different economic environments,
- different target taste profiles,
- nutritional profiles, or
- other specifications that are specific to a time or place or need.
The Nutritional Formula is dependent on the target Cultivar Measurement Factors, the Variety being grown, the time of day, the time in the growth cycle or time between harvests, the growth being achieved, and the current values of the various sensors.
Our Growing Systems enable the scientific method to be applied to the growing of any variety, which will enable, by a qualified researcher, the identifying of potential causes and effects when growing a plant.
Oxygen is an essential plant nutrient – plant root systems require Oxygen for aerobic respiration, an essential plant process that releases energy for root growth and nutrient uptake. Oxygen requirements for plants in flower tend to be more demanding in comparison to vegetative states, and differ based on the size of the root system, temperature, and nutrient uptake rates, and the specific stage of growth. Injury from low (or no) Oxygen in the root zone can take several forms and these will differ in severity between plant types.
Often, the first sign of inadequate Oxygen supply to the roots is wilting of the plant under warm conditions and high light levels. Insufficient Oxygen reduces the permeability of the roots to water and there will be an accumulation of toxins, so that both water and minerals are not absorbed in sufficient amounts to support plant growth.
In our Growing Systems, Oxygen is delivered to the roots through the way the Nutrients are delivered to the plants. The Oxygen in water is measured by the dissolved Oxygen (DO) level, which is vital for the health and strength of the root system as well as being necessary for nutrient uptake. Plants breathe just like all organisms via respiration. Common understanding is that plants produce Oxygen from CO2, but, the overall amount of Oxygen used is dwarfed by the amount produced by photosynthesis.
In our Growing Systems, the Oxygen supplied for plant root uptake is provided by Dissolved Oxygen (DO) located in the Nutrient Solution and as part of the Nutrient Delivery Formula. Solubility of Oxygen in water depends on the water temperature, the partial pressure of Oxygen, the atmospheric pressure, the salinity of the liquid and the area of liquid exposed to the air. Under normal conditions (20 C, 1 atmosphere of pressure and air with a normal Oxygen content), the maximum amount of dissolved Oxygen is 9 ppm.
The Atmosphere Formula specifies the Growing Room air temperature and humidity, Growing Unit air temperature and Humidity, and management of Growing Room VPD (Vapor Pressure Deficit), as well as Growing Unit VPD, management of Air Flow velocity, volume direction, oxygen content, and level of CO2. The Atmosphere Formula is delivered through the Atmosphere Subsystem with specific values for a particular Variety and the Environment Control Unit for the Growing Room or group of Growing Units within the Growing Room. The Atmosphere Formula primarily is for the Inter-Harvest Time period, it will be adjusted during Harvest Time.
The Lighting Formula consists of the DLI (Daily Light Integral), the specific spectrum used, the length of time a spectrum is given to the plants, the intensity of the light, and the order in which each spectrum will be presented. For example, to simulate a full day light schedule, the beginning (simulated dawn) spectrum will be different than end (simulated dusk) spectrum. During the middle (simulated morning, mid-day, and afternoon) the spectra will change. The Lighting Formula can be changed to maximize the efficacy of any Cultivar Measurement Factor for the Cultivar.
Our Lighting Formula is unique to a Variety and Cultivar Measurement Factor. The Lighting Formula can be used to simulate any daylight sequence in the world. Thus when growing a specific type of grape, a California light or Southern France light can be simulated to enable the grape to be used for a French style wine or a California style wine.
A Lumen is a measure of the total quantity of visible light emitted by a source. Lumens (or alternatively Foot-candles) is a “photometric” measurement based on the amount of visible light detected by the human eye, and is not intended for measuring plant photosynthesis requirements. Lumens provide an instantaneous light intensity at the time the reading is taken, which provides a measure of the amount of light produced by a specific lighting system. A group of lights together can be summed up for a total number of Lumens produced. As light travels in many directions it is also possible to measure the amount of light of many sources arriving at a specific spot. The distance from a point source of light, the amount of light energy diminishes according to the square of the distance (the inverse square law). Thus the difference between 12 inches and 11 inches from a light source is significantly different than the difference between 6 inches and 5 inches. Therefore, the distance from the light source and the plant is significant. The amount and specific light frequencies delivered to the plant is a form of electromagnetic radiation and varies in duration (energy over time), quality (wavelength or color), and intensity (the amount of light at each wavelength or color).
Lumens are used to measure the amount of light produced by the Lighting Unit component of our Growing Systems.
Photosynthetically Active Radiation (PAR)
In growing, the important measure of light is Photosynthetically Active Radiation (PAR). Current scientific literature believes PAR is best measured by light with a wavelength between 400 to 700 nm. Increasing energy in the PAR range increases plant photosynthesis, (the plant’s most basic metabolic process). Each Variety and Cultivar crop has an optimal light intensity that maximizes photosynthesis and plant growth. Without enough light growth, quality declines. And when there is light beyond a specific point for a specific Variety, there is no additional photosynthesis or growth. The total amount of PAR over a specific time is computed in the DLI portion of the Nutrition Formula. In summary, Lumens is the measure of the light coming from the Lighting Unit and the PAR is the measure of that light as it falls on a specific plant located in a Tower.
Daily Light Integral (DLI)
In nature, natural light continuously changes and a single measurement in time does not represent the amount of light a plant has received in a day. Instantaneous light is micromoles (μmol) per square meter (m2) per second (s-1), or: μmol·m2s-1 of PAR. This “quantum” unit quantifies the number of photons (individual particles of energy) used in photosynthesis that fall on a square meter (10.8 square feet) every second. This light measurement is also an instantaneous reading. Daily Light Integral (DLI) is the amount of PAR received each day as a function of light intensity (instantaneous light: μmol·m2·s-1) and duration (day). It is expressed as moles of light (mol) per square meter (m2) per day (d-1), or: mol·m2·d-1 (moles per day). In the Nutrition Formula, a specific Variety will receive a unique DLI.
The Nutrient Solution is a formula composed of a liquid, Dissolved Oxygen, temperature, and Plant Nutrients. In our Growing Systems, water (H2O) treated to remove all microbiological load is the preferred liquid. The specific Nutrient formula changes according to the Variety being grown in the Growing Unit and the Plant Growth Stage. As the plants are continuously growing and changing they need different amounts of nutrients, thus the formula for the Nutrient Solution is continuously changed. The formula can be adjusted if the plant is receiving light (performing photosynthesis) or not. The formula is established for a particular Variety in the Variety Nutritional Formula. Different versions of our Growing Systems enable the plants to receive a certain specific Nutrient Solution on a specific day within the Plant Growth Stage.
Nutrient Delivery Formula
The Nutrient Solution is delivered to plants through the roots using the Nutrient System. The actual amount of Nutrient Solution delivered to the Tower is based on the pump, the number and size of the apertures, the length of time the pump is operating and the frequency with which the pump operates. When the Nutrient Solution is not being delivered to the Nutrient Delivery Chamber the Nutrient Solution provided previously to the Tower drains via gravity. This allows the Substrate to dry and roots to receive oxygen.
Plant Growth Stage
Plant growth is separated into different stages:
a) Nursery Stage – From seed to first harvest.
b) Continuous Harvest Stage – For continuous harvest crops, the time during which the vegetables are harvested.
c) Inter-harvest Period – From Harvest to Harvest. This time period can be between 7 and 22 days for Cut-And-Come-Again harvested crops. The Inter-Harvest Period is measured in days, and the Nutritional Formula is modified to reflect the number of days after a harvest and before the next harvest. The plant needs recovering time immediately after each harvest. Each Variety is known to have a different recovery time period.
Nutrients refer to Macro-Nutrients and Micro-Nutrients needed by the plant. The terms Macro and Micro refer to the relative volume of the elements within the Nutrient Solution. The percentage of a specific macro-Nutrient is significantly higher than the Micro-Nutrient. The amounts of a specific nutrient are dependent on the amount expected in the harvested cultivar and variety plant as well as a ratio between certain elements. Each Variety has a unique and specific amount of Macro and Micro-Nutrients depending on which Cultivar Measurement Factor being optimized.
Macro-Nutrients and Micro-Nutrients
Macro-Nutrients include: Carbon (C), Hydrogen (H), Oxygen (O) provided by the air and as CO2 through the Atmosphere Subsystem and Water (H2O) in the Nutrient Solution. Explicitly added in the Nutrient Solution is Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulfur (S). The Micro-Nutrients added to the Nutrient Solution include Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo) and Zinc (Zn). The specific amounts and the ratio of each element to each other are specific to a Nutritional Formula for a Variety.
The Airflow refers to the movement the air in the plant canopy. The Airflow requirement is specific for a Variety. Too high an Airflow will increase plant Respiration rate beyond the Transpiration rates and cause plant stress. Too low an Airflow will reduce Transpiration and affect the efficacy of the Cultivar Measurement Factors. The Airflow is managed by the Atmosphere Subsystem. Airflow can be used to create a wind-like environment, which will effect the turgidity of the plant, which affect the “crunch” of certain leafy vegetables. The Atmosphere Subsystem can also be used to release the CO2 directly into the canopy area.
Many fruiting plants require pollination. In the wild they require wind, insects, and or animals. The density of the planting in the current versions of our Growing Systems enable an increased Airflow to act as simulated wind for pollination. The efficacy of this method is dependent on the Variety. The Airflow within our Growing Systems is strong enough to assist in the pollination of the plants.