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The nutrient content of a plant can be assessed by testing a sample of tissue from that plant. These tests are important in agriculture since fertilizer application can be fine-tuned if the plants nutrient status is known. Nitrogen most commonly limits plant growth and is the most managed nutrient.
Tissue tests are almost always useful, since they provide additional information about the physiology of the crop. Tissue tests are especially useful in certain situations;
Traditional tissue tests are destructive tests where a sample is sent to a laboratory for analysis. Any laboratory test (soil or tissue test) performed by a commercial company will cost the grower a fee. Laboratory tests take at least a week to complete, usually 2 weeks. It takes time to dry the samples, send them to the lab, complete the lab-tests, and then return the results to the grower. This means the results may not be received by the grower until after the ideal time to take action. [1] Nitrogen tissue tests that can be performed quickly in the field make tissue testing much more useful. [1]
Another issue with laboratory tissue tests is that the results are often difficult to interpret.
Non-destructive tissue tests have advantages over traditional destructive tests. Non-destructive tissue tests can be performed easily in the field, and provide results much faster than laboratory tests. [1]
To non-destructively assess nitrogen content, one can assess the chlorophyll content. Nitrogen content is linked to chlorophyll content because a molecule of chlorophyll contains four nitrogen atoms.
Nitrogen deficiency can be detected with a chlorophyll content meter.[ citation needed ] The meters determine chlorophyll content by shining a light through a leaf inserted in a slot and measuring the amount of light transmitted.
Chlorophyll meters use different units of measure. For instance, while Minolta uses "SPAD units", Force-A uses the Dualex Unit and ADC uses a Chlorophyll Content Index. All measure essentially the same thing, and conversion tables are available. [2]
While traditional absorption instruments have been very popular with plant scientists and have proved to work well with broad leaf species, they do have limitations. Limitations of absorption meters:
There are therefore samples which are not suitable for the absorption technique, these include small leaves, most CAM plants, conifer needles, fruit, algae on rocks, bryophytes, lichens and plant structures like stems and petioles. For these samples it is necessary to measure chlorophyll content using chlorophyll fluorescence.
In his scientific paper Gitelson (1999) states, "The ratio between chlorophyll fluorescence, at 735 nm and the wavelength range 700nm to 710 nm, F735/F700 was found to be linearly proportional to the chlorophyll content (with determination coefficient, r2, more than 0.95) and thus this ratio can be used as a precise indicator of chlorophyll content in plant leaves." [3] The fluorescent ratio chlorophyll content meters use this technique to measure these more difficult samples.
Fluorescent ratio chlorophyll content meters have the following advantages:
By measuring chlorophyll fluorescence, plant ecophysiology can be investigated. Chlorophyll fluorometers are used by plant researchers to assess plant stress.
Chlorophyll fluorometers are designed to measure variable fluorescence of photosystem II, or PSII. With most types of plant stress, this variable fluorescence can be used to measure the level of plant stress. The most commonly used protocols include: Fv/Fm, a dark adapted protocol, Y(II) or ΔF/Fm’ a light adapted test that is used during steady state photosynthesis, and various OJIP, dark adapted protocols that follow different schools of thought. Longer fluorescence quenching protocols can also be used for plant stress measurement, but because the time required for a measurement is extremely long, only small plant populations can probably be tested. NPQ or non-photochemical quenching is the most popular of these quenching parameters, but other parameters and other quenching protocols are also used.
Another test protocol based on fluorescence is the OJIP test. This method analyses the increase in fluorescence emitted from dark-adapted leaves when they are illuminated. The rise in fluorescence during the first second of illumination follows a curve with intermediate peaks, called the O, J, I, and P steps. In addition, the K step appears during specific types of stress, such as N-deficiency. Research has shown the K step is able to measure N-stress. [4]
Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, khloros and φύλλον, phyllon ("leaf"). Chlorophyll allow plants to absorb energy from light.
Hydroponics is a type of horticulture and a subset of hydroculture which involves growing plants, usually crops or medicinal plants, without soil, by using water-based mineral nutrient solutions. Terrestrial or aquatic plants may grow with their roots exposed to the nutritious liquid or the roots may be mechanically supported by an inert medium such as perlite, gravel, or other substrates.
A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.
Nitrogen deficiency is a deficiency of nitrogen in plants. This can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen available to break down carbon sources, making nitrogen unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.
Soil test may refer to one or more of a wide variety of soil analysis conducted for one of several possible reasons. Possibly the most widely conducted soil tests are those done to estimate the plant-available concentrations of plant nutrients, in order to determine fertilizer recommendations in agriculture. Other soil tests may be done for engineering (geotechnical), geochemical or ecological investigations.
Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig’s law of the minimum. The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil.
Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.
Nutrient management is the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimal nutrient use efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport of nutrients (fertilizer) that may impact the environment. It involves matching a specific field soil, climate, and crop management conditions to rate, source, timing, and place of nutrient application.
Water content or moisture content is the quantity of water contained in a material, such as soil, rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 to the value of the materials' porosity at saturation. It can be given on a volumetric or mass (gravimetric) basis.
Non-photochemical quenching (NPQ) is a mechanism employed by plants and algae to protect themselves from the adverse effects of high light intensity. It involves the quenching of singlet excited state chlorophylls (Chl) via enhanced internal conversion to the ground state, thus harmlessly dissipating excess excitation energy as heat through molecular vibrations. NPQ occurs in almost all photosynthetic eukaryotes, and helps to regulate and protect photosynthesis in environments where light energy absorption exceeds the capacity for light utilization in photosynthesis.
Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria. Excited chlorophyll dissipates the absorbed light energy by driving photosynthesis, as heat in non-photochemical quenching or by emission as fluorescence radiation. As these processes are complementary processes, the analysis of chlorophyll fluorescence is an important tool in plant research with a wide spectrum of applications.
Plant stress measurement is the quantification of environmental effects on plant health. When plants are subjected to less than ideal growing conditions, they are considered to be under stress. Stress factors can affect growth, survival and crop yields. Plant stress research looks at the response of plants to limitations and excesses of the main abiotic factors, and of other stress factors that are important in particular situations. Plant stress measurement usually focuses on taking measurements from living plants. It can involve visual assessments of plant vitality, however, more recently the focus has moved to the use of instruments and protocols that reveal the response of particular processes within the plant
Soil microbiology is the study of microorganisms in soil, their functions, and how they affect soil properties. It is believed that between two and four billion years ago, the first ancient bacteria and microorganisms came about on Earth's oceans. These bacteria could fix nitrogen, in time multiplied, and as a result released oxygen into the atmosphere. This led to more advanced microorganisms, which are important because they affect soil structure and fertility. Soil microorganisms can be classified as bacteria, actinomycetes, fungi, algae and protozoa. Each of these groups has characteristics that define them and their functions in soil.
The Indian Institute of Spices Research (IISR) is an autonomous organization engaged in agricultural research related to spices in India. The institute has its headquarters in Moozhikkal, Silver Hills, Kozhikode, Kerala and is a subsidiary of Indian Council of Agricultural Research (ICAR), New Delhi, under the Ministry of Agriculture, India.
The Dualex is an optical sensor developed by Force-A for the assessment of flavonol, anthocyanin, and chlorophyll contents in leaves. The sensor is a result of technology transfer from the CNRS and University of Paris-Sud Orsay. It allows to perform real-time and non-destructive measurements. The main applications are plant science and agriculture research.
Multiplex sensor is a hand-held multiparametric optical sensor developed by Force-A. The sensor is a result of 15 years of research on plant autofluorescence conducted by the CNRS and University of Paris-Sud Orsay. It provides accurate and complete information on the physiological state of the crop, allowing real-time and non-destructive measurements of chlorophyll and polyphenols contents in leaves and fruits.
Some types of lichen are able to fix nitrogen from the atmosphere. This process relies on the presence of cyanobacteria as a partner species within the lichen. The ability to fix nitrogen enables lichen to live in nutrient-poor environments. Lichen can also extract nitrogen from the rocks on which they grow.
Non-invasive micro-test technology (NMT) is a scientific research technology used for measuring physiological events of intact biological samples. NMT is used for research in many biological areas such as gene function, plant physiology, biomedical research, and environmental science.
Seventeen elements or nutrients are essential for plant growth and reproduction. They are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), nickel (Ni) and chlorine (Cl). Nutrients required for plants to complete their life cycle are considered essential nutrients. Nutrients that enhance the growth of plants but are not necessary to complete the plant's life cycle are considered non-essential. With the exception of carbon, hydrogen and oxygen, which are supplied by carbon dioxide and water, and nitrogen, provided through nitrogen fixation, the nutrients derive originally from the mineral component of the soil. The Law of the Minimum expresses that when the available form of a nutrient is not in enough proportion in the soil solution, then other nutrients cannot be taken up at an optimum rate by a plant. A particular nutrient ratio of the soil solution is thus mandatory for optimizing plant growth, a value which might differ from nutrient ratios calculated from plant composition.
A light-induced fluorescence transient (LIFT) is a device to remotely measure chlorophyll fluorescence in plants in a fast and non-destructive way. By using a series of excitation light pulses, LIFT combines chlorophyll fluorescence data with spectral and RGB information to provide insights into various photosynthetic traits and vegetation indices. LIFT combines the pump-probe method with the principle of laser-induced fluorescence.
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