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The Lotus Seed Survival Tactic
The seed of the Lotus ( Nelumbo sp. ) is a very hard nut and is almost completely impermeable to water. It remains viable for many years; some evidence indicates over two hundred years at least. If the seed is placed into an ideal habitat for growth, it may still remain dormant for many decades before sprouting. It seems almost counterintuitive that being resistant to sprouting has a survival advantage.
Researchers who have worked with the plant have theorized on why having seeds that are so difficult to germinate is advantageous to survival. The probable reasons for this survival tactic in the genus Nelumbo are two fold. The first is that when the lotus occupies an area, it spreads rapidly by vegetative means until every suitable site is covered. If a seed sprouts in such an environment, it will have little chance for survival because it will be shaded out. The second reason is that the tubers of the lotus are very nutritious. Humans also find them good food ( you can find them as a fresh or canned vegetable in Asian food markets) . If any aquatic herbivore ( muskrat, beaver) pair happens upon the growing site, it will establish a home there and raise a family of several generations until the entire stand is devoured. If the surviving dormant seeds then proceed immediately to germinate, the succeeding generation would also be eaten. Consequently, until the herbivores move out for lack of food, it is best for the seeds to remain dormant for a while. Nelumbo seeds are either round and the size of a green pea or oval and the size of a shelled peanut. One end of the seed has a sharp point which is the remains of the floral stigma. On the opposite end is a tiny dimple, a remnant of where the seed was attached to the mother plant The seed color can vary from gray to dark brown or black. The shell is very hard and consists of two layers which are tightly bonded together. Inside the shell are two paper thin brown colored seed coats which enclose the twin cream colored cotyledons. This feature is what places the Nelumbo genus into the Dicotyledon subclass of flowering plants ( Angiosperms) . Between the cotyledons is the Nelumbo embryo which consists of two prominent inrolled leaves with attendant stem. The leaves are doubled over against the stems because of the tight space. When the seed sprouts, the stems elongate to push the inrolled leaves up to the water surface. On the way up, the doubled over leaves straighten up and unroll after they reach the surface. There they become the round water- repellent floating leaves which are so characteristic of the Nelumbos. There are no intermediate underwater leaves that are typical for the waterlily family ( Nymphaeaceae) . This is one of the many reasons for the recent assignment of the Nelumbo genus into its own separate family, the Nelumbonaceae.
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