Exploring the limits of crop productivity: A model to evaluate progress

The goal was to determine the limits of crop productivity when all environmental constraints were removed. Researchers define productivity as food output per unit of input. Researchers evaluated cultivars of wheat with reduced leaf size and number to decrease the leaf area index at high plant densities. These cultivars may also have an improved harvest index. Hydroponic studies indicate that 1 mM nitrate in solution is adequate to support maximum growth in these systems, provided iron nutrition is adequate. Wheat does not accumulate nitrate in leaves even when the solution nitrate concentration is 15 mM. Long-term photosynthetic efficiency (g mol (exp -1) of photons) and harvest index were not altered by photoperiod (16, 20, or 24 hours). Wheat does not need, nor benefit from, a diurnal dark period

Three Challenges of Controlled Environment Research

A presentation given to show ways to grow plants in controlled research environments to more resemble plants found in the wild

Toward an optimal spectral quality for plant growth and development: The importance of radiation capture

We have characterized the effects of individual wavelengths of light on single leaf photosynthesis but we do not yet fully understand the effects of multi-wavelength radiation sources on growth and whole-plant net assimilation. Studies with monochromatic light by Hoover, McCree and Inada nearly a half century ago indicated that blue and cyan photons are used less efficiently than orange and red photons. Contrary to these measurements, studies in whole plants have found that photosynthesis often increases with an increasing fraction of blue photons. Plant growth, however, typically decreases as the fraction of blue photons increases above 5 to 10%. The dichotomy of increasing photosynthesis and decreasing growth reflects an oversight of the critical role of radiation capture (light interception) in the growth of whole plants. Photosynthetic efficiency is measured as quantum yield: moles of carbon fixed per mole of photons absorbed. Increasing blue light often inhibits cell division, cell expansion, and thus reduces leaf area. The thicker leaves have higher photosynthetic rates per unit area, but reduced radiation capture. This blue-light-induced reduction in photon capture is usually the primary reason for reduced growth in spite of increased photosynthesis per unit leaf area. This distinction is critical when extrapolating from single leaves to plant communities

Super Dwarf Wheat for Growth in Confined Spaces

USU-Perigee is a dwarf red spring wheat that is a hybrid of a high-yield early tall wheat (USU-Apogee) and a low-yield, extremely short wheat that has poor agronomic characteristics. USU-Perigee was selected for its extremely short height (.0.3 m) and high yield . characteristics that make it suitable for growth in confined spaces in controlled environments. Other desirable characteristics include rapid development and resistance to a leaf-tip necrosis, associated with calcium deficiency, that occurs in other wheat cultivars under rapid-growth conditions (particularly, continuous light). Heads emerge after only 21 days of growth in continuous light at a constant temperature of 25 C. In tests, USU-Perigee was found to outyield other full dwarf (defined as <0.4 m tall) wheat cultivars: The yield advantage at a constant temperature of 23 C was found to be about 30 percent. Originally intended as a candidate food crop to be grown aboard spacecraft on long missions, this cultivar could also be grown in terrestrial growth chambers and could be useful for plant-physiology and -pathology studies

\u27Super Dwarf\u27 Rice: Temperature Studies

Detailed temperature studies are a prerequisite to the optimization of crop productivity because field studies at ambient CO2 provide only a general guide to optimal temperatures. Meristem temperature has a profound effect on crop development rate, and the optimum temperature usually decreases as the crop matures. Previous studies with semi-dwarf rice (Ai-nan-tsao & 29-Lu-1) indicated that temperatures above about 33 ºC reduce seed set if they occur during anthesis. In rice, high temperatures are especially detrimental if there is rapid dark-to-light temperature increase. Conversely, average day/night temperatures in the mid 20\u27s delay heading and cause an undesirable increase in vegetative biomass. We examined 3 temperatures prior to anthesis (30/24; 32/26; & 34/28). Temperature of all treatments was decreased to 30/24 at 3-d prior to anthesis and further decreased to 28/22 during grain fill to prolong the duration of grain fill and increase harvest index. Vegetative biomass was increased by 10% per oC with increasing temperature, but seed yield was not significantly increased at the warmer temperatures so harvest index decreased. Super dwarf rice continues forming tillers throughout vegetative growth, presumably because of the lack of apical dominance caused by a lack of active gibberellic acid. At the relatively low plant density used in this study (100 plants per m2), many late tillers were formed and 25 to 30% of the heads were sterile. We are now conducting density studies and adding low levels of GA to the nutrient solution to decrease late tillers and improve harvest index

Double-Ended High Pressure Sodium Fixtures Decline less than 6% over 2 years and 5000 hours

Double-ended (DE) high pressure sodium (HPS) lights with electronic ballasts are reported to age more slowly than the old mogul base technology with magnetic ballasts, but aging has not been well studied in a greenhouse environment. Both dirt accumulation and age can decrease output

Phytoremediation: Physiological procedures for scaling from laboratory to field

Plants can increase the removal of organic compounds from soil by three basic mechanisms: rhizosphere degradation; uptake, translocation, and volatilization of unmetabolized compounds; and uptake, metabolism or storage. The importance of each of these mechanisms is typically estimated from measurements made on plants in containers in controlled environments or from field studies of single plants and it is necessary to scale this data to the community level. Over the past century physiologists have developed and refined procedures for scaling from measurements made in small chambers to determine mass transport in ecosystems. Here we review procedures and apply the principles to scaling from measurements of volatile and non-volatile contaminants in small chambers to plant communities. Numerical examples from measured literature values are given

Residue from Sequestrene 138 Fe EDDHA Clogs Filters: Alternatives for Chelated Iron in Liquid Fertilizer Systems

Ferric iron rapidly precipitates as FeOH and becomes biologically unavailable, so chelated iron is commonly used in liquid fertilization systems to keep it in solution. The most common chelating agents in agriculture are: EDDHA (ethylenediamine-N,N\u27-bis(2-hydroxyphenylacetic acid) DTPA (diethylenetriaminepentaacetic acid) EDTA (ethylenediaminetetraacetic acid) and for monocots in deep-flow hydroponics, HEDTA (also called HEEDTA

Diffuse Light Panels Slightly Increase Canopy Light Use Efficiency but Decrease Light Intensity and Canopy Photosynthesis of Lettuce

Over-absorption of light by the upper canopy limits light to the lower leaves and thus reduces canopy light use efficiency (photosynthesis per unit absorbed light). The objective of this study was to determine if increasing the fraction of diffuse light could increase canopy light use efficiency and photosynthesis

Optimizing Concentrating Mirrors and Fiber Optics for Food Production on Mars

Growing food on Mars for long-term space exploration has many benefits including reduced costs and fuel requirements for lift-off, increased nutrition and psychological benefits for astronauts, and oxygen and water regeneration. However, there are also many complication including potential threats caused by the thinner atmosphere, which would force production underground or into a heavily armored base. Fiber optics and concentrating mirrors for photon delivery provide a more efficient system than more traditional electric systems. This technology transmits solar radiation, and the spectra can be altered by tuning the mirrors to only transmit photosynthetic photons. In order to reduce heat loads and optimize food production it is important to determine whether ultra-violet and far-red photons should be included or excluded from this system. The photons in this range can be either beneficial or detrimental depending on the crop, timing and intensity