Orchids are the most fascinating plants in the entire plant kingdom. Even after more than a century of detailed study, many characteristics and behaviours of orchid plants are not documented or studied in detail.
Orchid blooms appear with duplicate floral parts – 2 lips, 2 spurs, 4 petals, 6 sepals, 2 columns etc. In some cases duplication of all flower parts happens in the same flower, but more frequently only one or two parts get duplicated. Interestingly, not all the flowers on an inflorescence show this variation, maybe a single flower to a few flowers show this freak appearance. This is due to mutations during the flower development.
Mutations in flowers are caused due to a limited gene-pool or some environmental factors. However, this phenomenon is so rare that the chances of finding an orchid plant with monstrous or freak flowers are 1 in 10,000 plants.
Several orchid species are deciduous, meaning they shed their leaves for some part of the year. Shedding of leaves helps the plant survive water loss in varying weather conditions. At the same time, many species tend to flower while they remain leafless. Flowering during leafless season increases the chances of better pollination and wind transmission of seeds.
Presented here is Dendrobium aphyllum (Roxb.) C.E.C.Fisch., during monsoon and winter months.
In orchid flowers, the basal part of the lip is often lobed, curved up to form a narrow structure with the column running along its open upper side. The apex part of the lip plays the role of a landing pad where the pollinator lands. The odour of the flower, the presence of pseudopollen, or the nectary glands make the pollinator crawl further inside. The anther cap is attached in such a way that it allows the pollinator to move forward without any obstruction. As the pollinator forces its way back, the pollinarium gets attached to the thorax of the pollinator and carried away.
(Note: Explained here is one of the several methods of the process of pollination in orchids.)
Ants are not known pollinators of any orchids. However, ants and orchids keep a mutually beneficial relationship – a complicated process least studied in the eastern Himalaya.
It has been recorded during my work that certain species of orchid flowers attract ants even before they open. The presence of ants scare away many insects that damage or fully destroy buds and flowers while they hunt for nectar, thus affecting the process of pollination and seed production.
As flowers play a critical role in the survival of many species, orchid plants developed the system by which they attract certain species of ants with their nectar and in-turn the ants help in protecting the flowers from many damage causing insects.
It is interesting to note that those insects that cause no damage to buds and flowers are not being attacked by ants. Indeed these friendly insects are mostly pollinators of these species.
The apex (point away from its attachment) of the spur is generally pointed, round, obtuse, or rarely truncated. However, few orchid flowers produce spurs with its apex bilobed (also referred to as 2-lobed).
The reasons that make the apex of the spur unique is a topic least researched. However, it has to be believed that this characteristic is related to certain pollinator behaviour.
Generally orchids are glabrous (smooth and hairless) plants. However, hairy characteristics in orchids are not uncommon, it can be very minute to a cm long, soft to stiff, silky to shiny etc., on stem, raceme, leaf, flower parts etc. What may be, all types of hairy outgrowths are whitish.
Rarely few orchid species are with brownish hairs. It is a characteristic seen only in a few genera.
In resupinate orchid flowers, when buds are formed they are upside down – meaning the lip and spur (if present) are on top side of the bud. As the buds develop, the pedicel twists either clockwise or anti-clockwise to invert the bud, thus arranging the lip and spur to the bottom side of the flower. This arrangement helps visiting pollinators.
(Note: Pics of spurred buds are used to make the lesson more easier).
Spur is the hollow slender extension from the base of the lip. Its length and size varies from species to species. It can be a minute globose to a few cm long cylindrical structure. Spurs are often straight, pendulous or slightly curved toward its apex in arrangement.
However, a few species in genera Aerides produce uncommon perpendicularly bent triangular shaped spurs.