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Plastochron
As the tip of a plant shoot grows, new leaves are produced at regular time intervals if temperature is held constant. This time interval is termed the plastochron (or plastochrone). The plastochrone index and the leaf plastochron index are ways of measuring the age of a plant dependent on morphological traits rather than on chronological age. Use of these indices removes differences caused by germination, developmental differences and exponential growth. Definitions The spatial pattern of the arrangement of leaves is called phyllotaxy whereas the time between successive leaf initiation events is called the plastochron and the rate of emergence from the apical bud is the phyllochron. Plastochron ratio In 1951, F. J. Richards introduced the idea of the plastochron ratio and developed a system of equations to describe mathematically a centric representation using three parameters: plastochron ratio, divergence angle, and the angle of the cone tangential to the apex in the area being ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf Plastochron Index
Leaf plastocron index is a measure of plant leaf age based on morphological development (the plastochron). It is useful in studying plant development requiring destructive measurement on multiple individuals. By measuring a metric against morphological age, instead of chronological time, one can reduce variations occurring between individuals, thus allowing greater focus on variations due to development. What is the leaf plastochron index? The leaf plastochron index, also referred to simply as the plastochron index (PI) as it is derived from, is a demography formula used to determine the developmental age and growing rate of a leaf or other growing plant organ.Erickson, R. and Michelini, F., 1957. THE PLASTOCHRON INDEX. American Journal of Botany, 44(4), pp.297-305. This formula was useful when first introduced as it allowed scientists to be able to track the progression and growth of a plant. According to ''American Journal of Botany'', the typical variation of the formula for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shoot (botany)
In botany, a plant shoot consists of any plant stem together with its appendages like leaves, lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spring, perennial plant shoots are the new growth that grows from the ground in herbaceous plants or the new stem or flower growth that grows on woody plants. In everyday speech, shoots are often synonymous with stems. Stems, which are an integral component of shoots, provide an axis for buds, fruits, and leaves. Young shoots are often eaten by animals because the natural fiber, fibers in the new growth have not yet completed secondary cell wall development, making the young shoots softer and easier to chew and digest. As shoots grow and age, the cells develop secondary cell walls that have a hard and tough structure. Some plants (e.g. bracken) produce toxins that make their shoots inedible or less palatable. File:Cucumber leaf.jpg, The sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllotaxis
In botany, phyllotaxis () or phyllotaxy is the arrangement of leaf, leaves on a plant stem. Phyllotactic spirals form a distinctive class of patterns in nature. Leaf arrangement The basic leaf#Arrangement on the stem, arrangements of leaves on a stem are opposite and alternate (also known as spiral). Leaves may also be Whorl (botany), whorled if several leaves arise, or appear to arise, from the same level (at the same Node (botany), node) on a stem. With an opposite leaf arrangement, two leaves arise from the stem at the same level (at the same Node (botany), node), on opposite sides of the stem. An opposite leaf pair can be thought of as a whorl of two leaves. With an alternate (spiral) pattern, each leaf arises at a different point (node) on the stem. Distichous phyllotaxis, also called "two-ranked leaf arrangement" is a special case of either opposite or alternate leaf arrangement where the leaves on a stem are arranged in two vertical columns on opposite sides of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllochron
The phyllochron is the intervening period between the sequential emergence of leaves on the main stem of a plant, also rendered as ''leaf appearance−1''. This measurement is used by botanists and agronomists to describe the growth and development of plants, especially cereals. The term phyllochron was first described in 1966. The interval between leaf appearances can be recorded in both standard measurements of time as well as thermal time (e.g. growing degree units). One phytomer unit is added over the course of one phyllochron. No significantly robust equation to predict phyllochrons has been developed. Variation Increases in phyllochron in cereals correlates with growing degree units in a slightly curvilinear fashion. In all cultivars of cereals, fluctuations in temperature are the primary factor that affects the length of the phyllochron. Less important secondary factors emerge in a number of different and sometimes contradictory studies on phyllochron response to variation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petiole (botany)
In botany, the petiole () is the stalk that attaches the leaf blade to the Plant stem, stem. It is able to twist the leaf to face the sun, producing a characteristic foliage arrangement (spacing of blades), and also optimizing its exposure to sunlight. Outgrowths appearing on each side of the petiole in some species are called stipules. The terms wikt:petiolate, petiolate and wikt:apetiolate, apetiolate are applied respectively to leaves with and without petioles. Description The petiole is a stalk that attaches a leaf to the plant stem. In petiolate leaves the leaf stalk may be long (as in the leaves of celery and rhubarb), or short (for example basil). When completely absent, the blade attaches directly to the stem and is said to be Sessility (botany), sessile or apetiolate. Subpetiolate leaves have an extremely short petiole, and may appear sessile. The broomrape family Orobanchaceae is an example of a family in which the leaves are always sessile. In some other plant group ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog to be present. Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is the dew point. The amount of water vapor needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of air decreases it will eventually reach the saturation point without adding or losing water mass. The amount of water vapor contained within a parcel of air can vary significantly. For example, a parcel of air near saturation may contain 8 g of water per cubic metre of air at , and 28 g of water per cubic metre of air at Three primary measurements of humidity are widely employed: abso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arid
Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata-Rocha, W., Monjardin-Armenta, S. A., Franco-Ochoa, C., & Zambrano-Medina, Y. G. (2021). The Identification and Classification of Arid Zones through Multicriteria Evaluation and Geographic Information Systems—Case Study: Arid Regions of Northwest Mexico. ''ISPRS International Journal of Geo-Information'', ''10''(11), 720. https://doi.org/10.3390/ijgi10110720 These areas tend to fall upon degraded soils, and their health and functioning are key necessities of regulating ecosystems’ atmospheric components. Change over time The distribution of aridity at any time is largely the result of the general circulation of the atmosphere. The latter does change significantly over time through climate change. For example, temperature increase by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoperiodism
Photoperiod is the change of day length around the seasons. The rotation of the earth around its axis produces 24 hour changes in light (day) and dark (night) cycles on earth. The length of the light and dark in each phase varies across the seasons due to the tilt of the earth around its axis. The photoperiod defines the length of the light, for example a summer day the length of light could be 16 hours while the dark is 8 hours, whereas a winter day the length of day could be 8 hours, whereas the dark is 16 hours. Importantly, the seasons are different in the northern hemisphere than the southern hemisphere. Photoperiodism is the physiological reaction of organisms to the length of light or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods. They are classified under three groups according to the photoperiods: short-day plants, long-day plants, and day ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
