PLANTS: HOW THEY LIVE AND HOW THEY ARE MADE
Unipar helical rope (Hypericum perforatum)
CIMA BIPARA OR DICASIO
Cima unipara scorpioid (Heliotropium europaeum)
INFIORESCENCE (fr. Inflorescence sp. Inflorescencia ted. Blütenstand ingl. Inflorescence). - The flowers of the Anthophytes or Phanerogams are isolated only exceptionally but are mostly collected in good numbers, with a given order of development and with a determined and constant arrangement for each plant, on systems of branches and twigs which are called inflorescences. These are distinguished from the ordinary vegetative ramifications above all for having their more numerous and denser branches and for the almost constant presence of scaly bracts and bracts, in whose axils are respectively the floriferous twigs and the single flowers.
Although it is generally easy to distinguish a flower from an inflorescence, however in some cases it is very difficult to understand if we are dealing with a single flower or with a complex of flowers as, for example, in the inflorescences of certain Conifers and especially in the very contracted ones of the Euphorbia.
The inflorescences, very complex and of very varied shapes but always distinguishable from the vegetative portion of the plant, are especially characteristic of the Angiosperms, to which the following information refers particularly. The production of branches in the region of the stem that bears the flowers takes place according to the same general laws that regulate it in the vegetative stems, therefore there is terminal and lateral branching and the latter, by far the most frequent, occurs with the two types of raceme or bunch and top. In the first case the main axis or rachis of the inflorescence (which in the section interposed with the flowers is called stalk) and possibly also its branches retain, at least potentially, the ability to continue to stretch indefinitely in the second case instead they lose more or less soon this capacity, because their apex ends directly in a flower, hence the distinction of two types of inflorescences: indefinite and definite. The former, due to the fact that in them the flowers in their subsequent development tend towards the apex of the stem which is the center of the figure of the inflorescence, are also called acropetes or centripetal, the latter, on the other hand, for similar reasons are called basipetes or centrifuges. Always in relation to the branching, the inflorescence can be simple or composed, according to whether the stalk bears the flowers directly or branches out in 2 °, 3 ° axes. order, either in its entire length, or only at its base, and only the last twigs give rise to the flowers.
In compound inflorescences it often happens that the subsequent ramifications instead of being all of the same type (homotypic or uniform inflorescences) may present different types mixed together (heterotypic or mixed inflorescences), such as, for example, in many Asteraceae and Graminaceae that they respectively have the typical flower heads and spikelet inflorescences gathered in corymbs, antelee, panicles and other complex types.
The varying length of the stalk and of the flower peduncles also contributes to giving their varied and characteristic appearance to the inflorescences. If these are so short that they appear to be missing, the flowers appear sessile, and if they have a visible length this may be the same for all or vary from one to the other. The stalk, which in general is more or less long, can in some cases remain very short and then, in order to insert the flowers, it acquires in width what it has lost in length and takes on a conical or hemispherical shape, or horizontally expanded into a plate and more or less concave cup, called common or overall receptacle to distinguish it from that of each flower. Sometimes the flattening of the stalk takes place from the sides rather than in a horizontal plane, such as eg. in Urtica membranacea and Celosia cristata commonly cultivated in gardens.
As for the single flowers, also for the inflorescences the position they occupy on the plant can vary. Generally they are terminal when instead they are lateral they usually appear in the axilla of the leaves (axillary inflorescences) or outside it - opposite or alongside - (extra-axillary inflorescences) or again in the bifurcations of the stem (wing inflorescences, for example, in the oleander). Sometimes there is also the case of originally axillary inflorescences which later become extra-axillary by displacement caused by successive growth phenomena.
Also the bracts and the bracts or profiles, in whose armpits the branches of the stalk and the single flowers are born respectively, can vary in shape, size, color, etc., up to completely missing in some cases (Crucifers). Mostly they are similar to the vegetative leaves of the plant, but diminished without petiole if those were provided, of the same herbaceous consistency as them and green in color. But in some cases the bracts, in number of one or very few, become very large and form a kind of foil, called spata, which embraces the base of the stalk, of a color or little or very different from green, preserving the herbaceous consistency ( Araceae), becoming parchment (Graminacee) and even woody (Palme). When gathered in large numbers thickly at the base of a contracted inflorescence such as that, for example, of the sunflower and other Compotes, they form together the so-called envelope, in which it often happens that the bracts join together for the margins. Finally, in several cases, especially when the flowers are small or otherwise inconspicuous, the bracts, in order to attract the attention of animals - especially insects - that have to visit the flowers, take on very bright colors which, even without becoming very large, they achieve the purpose (Lavandula stoechas, Bougainvillea spectabilis, Euphorbia pulcherrima).
C laxification. - On the basis of the aforementioned characters, the main and most frequent types of inflorescences can be classified according to the following table:
Homotypic or uniform inflorescences (with all branches of the same type).
A) R acemose or botrytic (indefinite, centripetal acropetal flowering).
1. Spiciformes (flowers borne by 1st order branches):
a) with elongated axis: spy, spadix, catkin or kitten, raceme or cluster, simple corymb
b) with shortened axis: flower head, calatide, syconous, simple umbrella.
2. Panicle (flowers carried by 2nd, 3rd order branches):
a) with elongated axis: panicle, thyrsus, spiciform panicle, compound corymb
b) with shortened axis: compound umbrella.
B) C imose (defined, with centrifugal basipetal flowering):
a) pleiocasius or multipara peak (umbrella-shaped top, antela)
c) monocase or uniparous peak (helicoid tip, scorpioid tip).
Heterotypic or mixed flowers (with several types of branches in the same inflorescence).
The salient characters of the aforementioned inflorescences in their typical forms are summarily the following:
Ear. - With sessile flowers on the sides of the elongated stalk (Plantago, Lavandula). The characteristic spikelet of Glumiflore and in particular of Graminaceae is a contracted spike that bears a few very simple flowers sometimes reduced to one, accompanied at its base by two scariose bracts, mutic or aristate, called glumes, and each flower by two bractoles, also scariose , called glumette or palee.
Spadix. - It is a variant of the ear in which the stalk, which generally bears diclinic flowers at its base, extends into a sterile, showy appendix of various appearance, accompanied and sometimes curled up by one or a few bracts (spathe) more or less large, of various texture and color (Spadiciflore: Aracee, Palme).
Catkin or Kitten. - It is also a variety of the spike which on a slender, flexible, pendulous stalk is thickly covered with diclinic flowers, mostly stamiferous, in which case after flowering the aament comes off completely and falls off (Poplar, Willow, Chestnut , etc.).
Raceme. - More commonly called cluster, fundamental form of indefinite inflorescences, on the sides of the more or less long stem it bears the visibly pedunculated flowers developing in acropetal series, so much so that sometimes, while the flower closest to the apex of the stem is still in button, those more distant they have already become fruits (Hyacinth, Ribes, etc.).
Corimbo. - It is a cluster in which the upper floral peduncles remain short and the lower ones gradually lengthen considerably, so much so that the flowers end up being all more or less in the same horizontal plane (Pear).
That the corymb is a shortened cluster is very evidently demonstrated by the inflorescence of many Crucifers - therefore called "corymbiform cluster" - which in the lower part, fully developed, is a genuine cluster, while at the apex, still in development, it ends in the form of a corymb.
Flower head. - Very common and polymorphic inflorescence with sessile flowers inserted on the extremity of the very short stalk which dilates in various ways to offer them an adequate insertion surface.
Sometimes simply clavate, conical or hemispherical (Trifoglio, Mulberry), sometimes expanded in a horizontal or even slightly concave plane (Dorstenia), the receptacle in most cases (Composte) expands in the shape of a plate, even very large (Sunflower), which bears the flowers above and below the envelope of bracts various in number, shape and size: and in this case it more properly takes the name of calatid. Then when the receptacle becomes so concave as to look like a wineskin with a fleshy wall, a small opening at the top and the underlying cavity covered internally by flowers, we speak of a syconium or hypoanthodium inflorescence (Fig).
Umbrella. - It is that inflorescence in which the flowers are all carried almost to the same height by peduncles of equal length which seem to be inserted at the same level on the very short stalk, almost null, accompanied at the base by the respective bracts forming the envelope (Cherry, Ivy, Primula).
Corn on the cob. -It is a compound cluster, that is, in which the flowers are not carried directly by the stem but by its branches of various orders. It varies in appearance according to the relative length of the branches: if they are all the same they give it an almost cylindrical configuration (black hellebore) if the middle ones are longer than the upper ones and the lower ones result in an ovate or fusiform shape, which some call thyrsus the Linnean definition is correct (Syringa vulgaris or lilac) but the most frequent form is the pyramidal one, to have the lower branches longer and the subsequent ones gradually shorter (Privet, Vine, Yucca), etc.
Then there is the spiciform panicle (Wheat, Barley), when the branches of the inflorescence are so short as to simulate a compound ear. The compound corymb and the compound umbel are nothing but slight complications of the same simple forms, mentioned above, for having the flowers carried by higher order branches forming many corimbetti or partial umbels (Achillea millefolium, Umbrelliferae).
The selvedge inflorescences, which also go by the overall name of cime, in which the apex of the stalk stops growing because it is defined in a flower under which branches sprout to which the further development of the inflorescence is entrusted, are distinguished in some types according to the number, length and orientation of the branches themselves.
We speak of pleiocase or multipara bud when the branches underneath the terminal flower are not less than three of dicasio or biparic bud when there are two and of monocasio or uniparous bud if there is only one. The branches of the 1st order can in turn end with a flower or produce branches of the 2nd order, from which very complex inflorescences come from which it is not always easy to recognize the selvedge nature, all the more so when the terminal flower that would document it can easily fall without a trace.
If in the pleiocase the branches are all of equal length, it has an appearance that resembles that of the simple umbrella and it is also called umbrella-like top (Euphorbia) if, on the other hand, the branches are of unequal length - the lower ones longer - and the flowers reach different levels, we have the Antela (Spiraea filipendula, Juncus, Scirpus).
In the dicasio or bipara tip, very regular, the only two branches that form immediately under the terminal flower, and which in turn then branch in the same way, grow and diverge equally so as to simulate a repeatedly forked apical branching (Centaurea minor, Cariofillacee ). In the monocase or uniparous top under the terminal flower, a single branch emerges which in turn ends in a flower and develops a single branch under it, and so on. These branches, which initially have an oblique position, then tend to move, placing themselves in a rectilinear position and simulating a single axis which botanically is called sympodium (meeting of several feet or axes of different order). The monocase is presented in two main forms depending on whether the branch develops alternately to the right and to the left or constantly on the same side, giving rise in the first case to the so-called uniparous helicoid peak (Alstroemeria, Hemerocallis) and in the second to the c. u. scorpioid (Hyosciamus, Symphytum, Heliotropium). That is vertical, while this is notoriously wrapped around itself like a crosier. Some modalities of these can still be distinguished according to the floors that occupy the successive branches with respect to each other (Bostrice, Drepanio, Cincinno, Ripidio).
Various of the aforementioned inflorescences, especially the dicasio and the antela, due to the extreme brevity of the peduncles can take on a spheroidal shape reminiscent of the flower head and which is called glomerulus (Parietaria, Valerianella, many Labiates).
It was Charles Linnaeus, the great Swedish naturalist who coined the term many of the scientific names still used today in botany 'Inflorescentia'. The word comes from the late Latin inflorescence which literally means to flourish.
Linnaeus also began to observe in the angiosperms the various types of inflorescence, to describe them in detail and catalog them. Let's see in detail what it is and let's try to understand which botanical characteristics they refer to. The magnificent cluster inflorescence of the wisteria
The flowers can be single or gathered in inflorescences. In inflorescences, the individual flowers are carried by a simple or branched axis (rachis).
The simple inflorescences consist of sessile or pedunculated flowers inserted on an unbranched axis. The main ones are:
• spike, the flowers are sessile (without peduncle) inserted alternately on a single axis (for example, the plantain)
• cluster (or raceme), like the ear, but with pedunculated flowers (for example, in alfalfa, sainfoin, black locust)
Compound inflorescences have the axis that has ramifications, the most important inflorescences of this type are:
• compound ear (for example, in wheat, rye, barley, triticale)
• corn on the cob or compound cluster (for example, in oats, rice, moss grass, vine)
• compound corymb (for example, in yarrow, rowan)
• compound umbrella (for example, in fennel, carrot).
It is important to consider that insects do not have the same perception of the flower as we do. To get an idea of what really attracts insects such as bees and butterflies we should subject the flower to the rays of ultraviolet light. In fact, for insects, in addition to color, it is a lot the shape is also important of the flower: this in fact greatly influences the way di pollination of the flower same.
A very important example that clarifies how important the shape of the flower is for the pollination process is that oforchid Orchis. The flower of this plant mainly attracts the males of some specific species of bees and hornets.
There corolla it has five brightly colored upper petals the central part of the lower petal almost looks like a "landing strip" with pistils and stamens placed in a privileged position. The pollen inevitably remains on the body of the insect, which will fertilize the next flower on which it will rest.
A similar fertilization is found in some aromatic plants belonging to the Labiate family, such as Rosemary and Sage.
This technique a little less clean but much more organic and natural plans to set up the same system that we used above a small uncovered jar and large container with lid, but instead of damp paper you can use peels and fruit or vegetable scraps. In fact, these waste parts of plants can donate moisture in a completely natural way. The ideal is to use citrus peels (well washed and dried) that have a pleasant aroma and above all do not tend (thanks to the presence of many essential oils) to generate mold or develop bacteria. Salad ribs or apple peels are also fine, even if they rot more easily and should be kept an eye on. The times for rehydration with fruit and vegetables are generally a little longer than those with moistened paper.
The floral part of a plant can be composed of a single flower or a set of inflorescences which branch off from a single peduncle.
Inflorescences are different: bunches, umbrellas, corimbri, tops, flower heads and sometimes they are mixed.
They are divided into two main groups: the racemose or indefinite, and the selvedges or defined and can be simple or composed.
They are the inflorescences in which the main axis as the lateral branches have a growth limited to the production of a flower.
They branch out so sympodial according to these main types:
The main types of compound inflorescences are: