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.^[1] The interval between leaf appearances can be recorded in both standard measurements of time as well as thermal time (e.g. growing degree units).^[2] One phytomer unit is added over the course of one phyllochron. No significantly robust equation to predict phyllochrons has been developed.^[3]

Variation

Increases in phyllochron in cereals correlates with growing degree units in a slightly curvilinear fashion.^[4] In all cultivars of cereals, fluctuations in temperature are the primary factor that affects the length of the phyllochron.^[3] Less important secondary factors emerge in a number of different and sometimes contradictory studies on phyllochron response to variation in light, CO₂ level, irrigation, nitrogen availability, salinity, soil properties, planting depth, planting time, and genotype.^[3][4] In cereals, the phyllochron may vary in speed between the main stem and the tillers.^[4] The phyllochron may or may not be equal to the length of time taken for one leaf to grow.^[2] It is more accurate to determine the value in a laboratory study than in the field,^[5] as field studies have not always noted the non-linear relationship of temperature and leaf appearance.^[3]

See also

• Phenology
• Phytomer
• Plant development
• Plastochron