In Encyclopædia Britannica, Research Paper Example

An interesting example of leaf modification in angiosperms, or, to be more precise, of shoot system modification, is presented by Epiphyllum – about 15 species of plants belonging to the family Cactaceae and native to tropical and subtropical America, i.e. living in warm and often dry areas. The common name for Epiphyllum – leaf cactus – stresses its peculiarity: mostly flattened, nonspiny stems that function as leaves (do the most part of photosynthesis).

There shoot system is characterized by cladodes (also referred to as cladophylls or phylloclades). It means that these plants do not develop leaves at all but in compensation their stems become flattened and perform photosynthetic functions. The stems are very pulpy and store water, which is especially important for desert plants.

In fact, Epiphyllum presents an example of the extreme reduction of leaves in Cactaceae. Instead of leaves, Epiphyllum produces thin flat cladodes that superficially resemble leaves. The stems are usually about 1-5 cm in width and 3-5 cm thick and often have lobed edges.

Obviously, the flattened form of stems provides larger green surface capable of photosynthesis. Unlike cacti, Epiphyllum is not covered with spines, but has hair bristles or tiny spines in the areolar. The areolar contains extra-floral nectarines – the so called areolar glands. These glands are located in the axils of the cladode and produce a nectar juice rich in sugar which attracts natural pollinators like ants.

Another leaf modification adopted by Epiphyllum is stolons, or runners, which are used to spread to a larger portion of a substrate and can grow upwards, downwards or laterally.

References

Angiosperm. Leaf Modification. (2009). In Encyclopædia Britannica. Retrieved May 25, 2009, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/24667/angiosperm

Epiphyllum phyllanthus. In The Exotic Rainforest. Retrieved May 25, 2009, from http://www.exoticrainforest.com/Epiphyllum%20phyllanthus%20subsp.%20phyllanthus%20pc.html

Leaf Cactus. (2009). In Encyclopædia Britannica. Retrieved May 25, 2009, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/333776/leaf-cactus