What are bromeliads: Difference between revisions

About half of the known Bromeliad species live epiphytic, meaning they grow on other plants, but without feeding on them. '''They are no parasites''', what they are often erroneously called and – alas - are treated likewise by locals. However Bromeliads can also be found living on rocks (litophytic) or on the ground (terrestrial). As their habitats dry out severely sometimes, some of them started building a funnel or a cistern with the use of the base of their leafs, to catch and keep water. The biggest species can this way store up several liters of water, which assists them to compensate rather long dry periods. At the same time these minuscule lakes represent a self-contained biotope and provide living space for several other creatures, often to the benefit of both. The funnels serve insect species as breeding place for their nymphs, tropical tree frogs live and spawn in them, and even several water plants grow there. Even crabs have been found in Bromeliad cisterns. In nutrient-poor regions a few Bromeliads actually have developed the ability to live as carnivores.  

Bromeliads are indeciduous, hardy herbaceous perennials. Rarely species occur which are deciduous in the dry season, like for example ''Pitcairnia heterophylla''. Her main shoot flowers only once and dies after the maturation of her seeds. This dieback takes place only gradually, because at the same time they produce replacing offshoots (called pups) which guarantee the continuance of the shoot system and can be used for multiplication. Only a few species die ultimately after bloom and maturity of the seeds. In the majority of cases the Bromeliads possess a compressed axis, of which results a leaf rosette as the typical shape. There exist some species though whose axis is not compressed and which develop small stems.

The parallel nerved foliage is arranged alternate and convoluted, less commonly distichous, like in the subgenus ''Diaphoramthema'' of the genus ''Tillandsia''. The leaves usually do not own a leaf stalk (with the exception of some ''Pitcairnia'' species). The edges can be straight or spiny. Some Tillandsias curl up their leaf apexes like a corkscrew in order to cling onto the surrounding boughs aud branches.

All representatives have in common the so called "absorbant hairs" or "scales" (foliar trichomes) on their leaves. Depending on habitat and way of life the scales enclose the leave partly or entirely and give it a striped design or a grey up to white shimmer. The pubescence thereby carries out more than one purpose. In sunny places they reflect the sunlight and by that they reduce the loss of water caused by evaporation. At the same time they multiply the surface of the leave to a great extent and thereby enlarge the accumulation of dew on the leaves in sites with low precipitation. The dew and it’s solute nutritive substances are absorbed by the trichomes like by blotting paper and are conveyed into the leave. Some Bromeliads have perfected this technique to an extend that they almost dispense with roots and subsist exclusively by way of the scales, like the well known Louisiana moss (''Tillandsia usneoides'').

Like all other monocotyledonous plants Bromeliads always have trifoliate flowers. That indicates that the number of all organs of the plant is divisible by three. That is: Three sepals, three petals, six stamens  and the ovary, consisting of three carpels. Often the signaling to attract potential pollinators is increased by very decorative bracts. Bromeliads predominantly have male and female flower organs combined in one flower. Only a small number of species produce unisexual flowers. They are called dioecious, meaning the whole plant is either male or female (f. e. the genera ''Androlepis'', ''Hechtia'' and some species of ''Catopsis'' and ''Aechmea''). In Bromeliads scent occurs regrettably seldom. The inflorescences are plain or compound racemes or panicles shaped very differently. Whereas the genus ''Neoregelia'' builds his flowers sunken deeply in the cistern, sometimes even hard to spot, the inflorescence of ''Puya raimondii'' with his thousands of individual flowers may be higher than 8 (!) meters. This species has, by the by, made it’s way into the “Guinness book of records” as the plant with the tallest inflorescence in the world.