As the tip of a plant
shoot
Shoot most commonly refers to:
* Shoot (botany), an immature plant or portion of a plant
* Shooting, the firing of projectile weapons
* Photo shoot, a photography session; an event wherein a photographer takes photographs
Shoot may also refer t ...
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
In botany, phyllotaxis () or phyllotaxy is the arrangement of leaves on a plant stem. Phyllotactic spirals form a distinctive class of patterns in nature.
Leaf arrangement
The basic arrangements of leaves on a stem are opposite and alterna ...
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 considered.
Orthostichy, Parastichy and Plastochrone Ratio in a Central Theory of Phyllotaxis
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Emerging phyllodes or leaf variants experience a sudden change from a high 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 t ...
environment to a more 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 ...
one. There are other changes they encounter such as variations in light level, photoperiod
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 season ...
and the gaseous content of the air.
References
Botany
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