Understanding The Environment There are three broad categories of environmental components interact to influence all life:
Understanding the many environmental factors and how they interact with each other to influence life is essential for good investigative science and is the key to successful experimenting with Fast Plants. Some environmental factors influence plant growth more than others. If one or more factors is reduced or increased such that normal development or functioning is disrupted, that factor is said to be limiting. In the case of Fast Plants, when a a factor is limiting the plants cannot grow to the best of their genetic ability and may appear stunted, diseased, or have difficulty reproducing. When a factor that can be measures becomes limiting, its observed effects can also be measured or quantified. Wisconsin Fast Plants Need 24 Hours a Day of Flourescent Light for Proper Growth and Development. Appropriate lighting is perhaps the most critical component of a plant's growing environment. Plants use energy from various regions of the visible spectrum to perform a number of functions essential to their growth and reproduction. Some seeds require red light to activate germination. Blue light is important for regulating elongation of stems and in guiding the direction of plant growth. Red and blue are the primary energy levels used for photosynthesis, whereas red and far red are important in the regulation of leaf expansion and certain pigment production systems. Light for Fast Plants is produced by fluorescent lamps which emit a mix of photons in the visible range that appear as white with warm (red) or cool (blue) tones in the mix. The quantity of photons reaching a surface is known as irradiance or photon flux density and is measured in micromoles (mM) or microEinsteins (mE) of photon flux per square meter per second. Irradiance of greater than 200 mEm-2s-1 is ideal for Fast Plants. Less than 100 mEm-2s-1 is inadequate. High light provides energy for photosynthesis to support the accelerated growth of the Fast Plants and also is the source of energy that regulates the form and color of the plants. Basic rapid-cycling Brassica rapa plants growing with normal nutrition and temperature under ideal lighting will be stocky and dark green with purple anthocyanin pigment strongly expressed in the stem, leaves and buds. The plants will bear many flowers which, when pollinated, will produce abundant seed in the normal life cycle of 35 to 40 days. Plants growing under the adequate, but less than ideal, will be somewhat less stocky and may require staking as the plants grow taller. Purple anthocyanin color will be less intense and seed set will be somewhat less than that from plants growing under higher light. Plants growing under less than adequate light will be spindly and tend to fall over easily. The leaves will be thinner and plants will have weak expression of the purple color in their stems and leaves. Such plants may not flower or will be delayed in flowering and will produce fewer flowers and seeds. Our experience with Fast Plants is that the more fluorescent light they receive, the better they grow. Fast Plants were purposely developed to grow under inexpensive, white fluorescent lamps and have been bred for many generations to perform well when illuminated continuously (24 hours/day) with the relatively high light intensity provided by either: Reflectors made from aluminum foil or reflective mylar (available from fabric or stationery stores) greatly increase the irradiance reaching the plants, particularly those around the edges of the lamps. Aluminum foil "curtains" (15 cm x 25 cm) taped on the lamp fixture to hang down to about the soil level will contribute to uniform lighting across the plants.
Keep the Fast Plants under constant 24 hour light to produce the best results. Be sure to make arrangements (with custodians, etc.) so light banks are not turned off at any time, especially on weekends. Ideally the growing tips of the plants should be kept 5 cm to 10 cm from the lights.
The temperature of the Fast Plants' growing environment will have an important influence on the growth of your plants. Temperatures that are too high or too low can affect the timing of developmental events such as seedling emergence and flowering. Optimal temperature is between 22°C and 28°C (72°F to 82°F).
Temperatures can be monitored under each bank using hi-low thermometers. Note fluctuations in the room temperature and variation in temperature among light banks.
The recommended "soil" is a mixture of one part peat moss and one part vermiculite, known as peatlite, serves as the root medium that anchors the plant roots, providing support for the stem and leaves. Physical characteristics of the root medium must be such as to provide adequate capillary wicking of water to the absorptive surfaces of the root hairs and epidermal cells, yet there must also be adequate channeling within the matrix of the root medium to enable air exchange for oxygen diffusion to the growing roots. Water: Water functions in many ways in plants, serving as the primary solvent supporting life's metabolic processes, generating turgor pressure (water pressure) for cell enlargement and growth, maintaining ionic balance and providing cooling via transpiration. Water is also the source of hydrogen reducing power when it is split by light energy in photosynthesis. Water enters the plant primarily through the root epidermis and hair cells, traveling through intercellular space and cortical cells to the xylem tissue where it is distributed throughout the plant. Within the root zone, water is found adhering to soil particles as a continuous film created through the cohesive forces of the water molecules. The adhesive forces that attract water molecules to the surfaces of soil particles and plant root cells pull the water into the minute channels within the soil and plant tissues via capillarity.
In Wisconsin Fast Plants growing systems, capillary wicking material is used to pull water from a reservoir to the root medium (soil) which has strong capillary properties. There is an unbroken continuity of water from the soil into and throughout the plants. (See figure at right.) Through this water course, the plant also gains access to inorganic nutrients. Gravity acts as a vertical counter force opposing the cohesive forces of water and adhesive forces of capillarity.
The atmospheric relative (RH) humidity of a classroom can affect the rate of transpiration and water uptake by plants. Under low relative humidity there can be rapid water uptake from the reservoirs. When reservoirs run dry, capillarity is broken and plants will desiccate and die. When plants begin to wilt, it is an indication that transpiration is exceeding water uptake. In some climates this occurs when there has been a rapid drop in atmospheric relative humidity. In these cases plants usually adjust by reducing transpiration and regaining their turgor pressure. If wilting persists in a Wisconsin Fast Plants growing system, check the reservoir and examine the capillary wicks and matting to be sure they have not dried out and broken the capillary connection between roots and reservoir. If the atmospheric relative humidity is very high (>95% RH), mature anthers in flowering Fast Plants may fail to open (dehisce) to expose their pollen. This occurs when plants are grown in closed containers in which the relative humidity builds up. It can be remedied by circulating air over the plants with a fan; mature anthers will then usually dehisce within a few minutes.
Inorganic nutrients are added to the root media in a balanced nutrient mixture, such as PetersŪ Professional All-Purpose Plant Food, water soluble 20-20-20 N-P-K plus minor elements. PetersŪ Professional contains available NPK at 20% by weight (20-20-20). Primary nutrient sources are urea, ammonium, phosphate, and potassium nitrate plus minor elements. A soluble blue dye is added or mixing.
A standard Fast Plants nutrient solution contain 7 grams of PetersŪ 20-2-20 fertilizer powder per liter of water, The nutrient solution can be applied to the growing substrate at the rate of 2 ml of solution on days 3, 7, 14, 21, and 28 for each plant that will be grown to maturity. If nutrients are added to the water reservoir in a continuous nutrient culture, the standard PetersŪ solution should be diluted to 1/8 strength.
Ambient air contains nitrogen (78%), oxygen (21%), hydrogen and helium (<1%). Carbon dioxide in air is approximately 350 parts per million and is the primary source of carbon incorporated into organic molecules via photosynthesis. Controlling Undesirable Pests: Fungi and bacteria rarely attack the above-ground parts of plants as long as the relative humidity is less than 95% and there is good air flow. The best control for fungi and bacteria is sanitation. Be sure to use pathogen-free root media (soil)- most commercially available peatlite mixtures are sanitized and pathogen-free. Keep the root media well aerated and drained by not packing it in the growing containers. After growing, it is important to rinse, then soak all pots, reservoirs, capillary mats and wicks for at least 30 minutes in a 10% chlorine bleach solution. Do not reuse root media.
The continuously illuminated plants can be attractive to many insects, especially at night. Daily surveillance and removal of insects is good practice. Sticky yellow pest control cards work well to trap incoming insects and flies emerging from the soil. The sticky strips available from garden stores can be cut and stapled to bamboo grilling skewers and mounted in film cans filled with sand and placed among the plants. These are very effective for white flies, aphids, fungus gnats and thrips. If colonies of aphids, white flies or thrips appear or evidence of larval feeding is observed (holes chewed in leaves or flowers), plants may be sprayed with insecticidal soap or another safe chemical control agent. Read labels carefully before applying chemicals. Surveillance and careful removal by hand is the best control practice. Keep insects under control if possible to prevent the spread of disease.
The most common residents with Fast Plants are algae. Most do not affect plant growth but can become unsightly and occasionally will build up in reservoirs and wicking to consume nutrients and retard water flow. Algae growth can be suppressed by adding copper sulfate (CuSO4.5H2O) to the nutrient solution at a final concentration in the reservoir of between 50 and 100 parts per million (milligrams/liter). You probably have algae if you notice a green, moldy-type layer on the surface of the soil. Fast Plants can be grown in a variety of different growing systems and under different lighting options. The three most common growing systems and lighting systems are: |
