Angiosperms are the most developed flowering plants that have ovules enclosed in diploid tissues (Fathima, Shantha & Rajagovindan, 2007). These species of plants bear seeds encapsulated in ovaries which eventually mature into fruits. In Taxonomy, they fall under the class Angiospermae, or division Anthophyta or Magnoliophyta. The diversity is enormous as there are over 250,000 species. These different species are adapted to the environment as is manifested in the structural modifications of leaves, flowers, roots and stems. The structural modification of the yellow water-lily (Nuphar lutea), a hydrophyte will be reviewed. Hydrophytes include plants that live in water or substrates that are partially anaerobic as a result of excess water.
The plant is found in an aquatic environment, and has structural modification to survive in this environment. The leaves are large and wide to increase the surface area for transpiration as there is no need to conserve water. They have a very thin cuticle as there is no need to conserve moisture (Menezes, 2000). This is unlike xerophytes which have a thick waxy cuticle to conserve moisture. In addition the leaves have aerenchymas which are sets of small cells that are arranged to form very big air spaces. This is in the place of parenchyma/sclerenchyma which are plant tissues which offer mechanical strength. The air is essential in bolstering buoyancy as the water lily is spongy, soft and very light. Oxygen is essential but it is not readily soluble in water unlike carbon dioxide. The aerenchyma serve as oxygen reservoirs and they also transport oxygen to the parts submerged in water from the aerial parts. This process is aided by the water currents that are responsible for plant movement. Thus, the dense aerenchymas play a significant role in both flotation and gaseous exchange.
Consequently, the water lily remains afloat and is well exposed to light for the purpose of photosynthesis. The plant can form sufficient simple carbohydrates via photosynthesis due to the large presence of aerenchyma. Moreover, the aerenchyma has partition walls, and this greatly contributes to the plant’s mechanical strength.
Light penetration is aided by the possession of very thin leaves (Menezes, 2000). In addition, the yellow water lily has dense epidermal cells which are endowed with chloroplasts. The root system of water lilies is significantly reduced as there is ample water. Moreover, the root hairs are not existent on the roots. There is no need for an extensive root system to aid in water uptake. The inflorescence is strategically located at the top of the water surface. This is atop the floating leaves. This bright yellow inflorescence attracts flies which aid in pollination. Alcohol produced by the water lily can freely diffuse in the air and attract flies. After pollination, the flower develops into a green fruit that is bottle-shaped. It contains numerous seeds and the bottle shape is highly susceptible to disruption by the water currents upon maturation. This greatly aids in the process of seed dispersal by the water currents (Menezes, 2000).
Stems of the yellow water lily and roots grow horizontally at the bottom of the submerged water, and the petioles of the leaves grow upwards. This allows the plant’s length to extend up to over 5 meters. The floating leaves have a side out of water and another side submerged in water. Numerous stomata are found on the leaf part exposed to the atmosphere. This allows transpiration, and is the opposite of many terrestrial plants that have numerous stomata on the lower part of the leaf. The location of numerous stomata on the unexposed part of the leaf reduces the rate of transpiration thereby conserving water (Sakshield Education. n.d.).