Young Blonde Girl With Blue Eyes Posing On Tree Trunks In The Deciduous Forest

In botany and horticulture, deciduous plants, including trees, shrubs and herbaceous perennials, are those that lose all of their leaves for part of the year. This process is called abscission. In some cases leaf loss coincides with winter - namely in temperate or polar climates. While in other areas of the world, including tropical, subtropical and arid regions of the world, plants lose their leaves during the dry season or during other seasons depending on variations in rainfall.
The converse of deciduous is evergreen, where green foliage is persistent year round. Plants that are intermediate, may be called semi-deciduous; they lose old foliage as new growth begins. Other plants are semi-evergreen and lose their leaves before the next growing season, but retain some during winter or during dry periods. Some trees, including a few species of oak have desiccated leaves that remain on the tree through winter; these dry persistent leaves are called marcescent leaves and are dropped in the spring as new growth begins.
Many deciduous plants flower during the period when they are leafless as this increases the effectiveness of pollination. The absence of leaves improves wind transmission of pollen for wind-pollinated plants, and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as the flowers can be damaged by frost or, in dry season regions, result in water stress on the plant. Nevertheless, there is much less branch and trunk breakage from glaze ice storms when leafless, and plants can reduce water loss due to the reduction in availability of liquid water during the cold winter days.
Leaf drop or abscission involves complex physiological signals and changes within plants. The process of photosynthesis steadily degrades the supply of chlorophylls in foliage; plants normally replenish chlorophylls during the summer months. When fall arrives and the days are shorter or when plants are drought stressed, deciduous trees decrease chlorophyll pigment production allowing other pigments present in the leaf to become apparent, resulting in non-green colored foliage. The brightest leaf colors are produced when days grow short and nights are cool but remain above freezing. These other pigments include carotenoids that are yellow, brown, and orange. Anthocyanin pigments produce reds and purple colors, though they are not always present in the leaves but are produced in the foliage in late summer when sugars are trapped in the leaves after the process of abscission begins. Parts of the world that have showy displays of bright autumn colors are limited to locations where days become short and nights are cool. In other parts of the world the leaves of deciduous trees simply fall off without turning the bright colors produced from the accumulation of anthocyanin pigments.