Floral formula states the structure of a flower utilizing numbers, letters and other symbols. The information provided by the floral formula can be very well represented by the floral diagram. The best quality of the floral formula is that it is unique to a family of plants or it can be made more specific for a particular species as well and it becomes the symbol for that particular family/species of flowering plants. For example, the floral formula of family Fabaceae is given by % ⚥ K(5) C1+2+(2) A(9)+1 G1.
Even though the above given floral formula of Fabaceae might seem just a bunch of symbols at first to you, it will seem fairly easy once you understand what these symbols mean. To understand the symbols let us first get to know about the description of flowering plants and later on it will be easier for you to comprehend the floral formula of Fabaceae family.
Floral Formula: A Semi-Technical Description of Flowering Plant
Now, all of us usually get an image of the flower and then the image of the plant in our mind whenever there is a mention of the name of a flower. But that does not seem to be an orderly representation or in any case a scientific representation. Such a description is usually very specific or either too general. If we consider the example of the tulip, the widely popular image that pops up in your mind is that of the yellow tulip. But that's just one particular case. There might be tulips of other colours and varied in numerous forms than one general idea. So, if all of the cases of tulips were to be represented as a whole from which you can get better reliable and factual information a scientific process needs to be in place. Thus, the floral formula and the floral diagrams are such semi-technical descriptions of flowering plants.
To describe various morphological features such as the habit, diverse vegetative characteristics like roots, stems and leaves, and floral characteristics and floral parts in a brief, simple and scientific way that too in a proper sequence, the floral formula is used. Floral diagrams can be considered as the pictorial manifestation of the floral formula. The one advantage of the floral diagram is that it also provides information regarding the relationship between various parts of the plant.
As discussed above, let’s have a look at the various symbols used in a floral formula.
Various Symbols Used in a Floral Formula
Using these symbols the floral formula describes the organs and their attributes for a certain flowering plant which is indicated by the letters and the numbers provide the counts of the different organs. If an organ is absent then the “0” is written in the subscript or the symbol for the organ is omitted from the formula and if the number is “many” (ranging from 10 - 12) then the symbol “∞” is used. Another symbol that is a very common part of any given floral formula is “+” which is used for the representation of the groups of units or whorls.
So, let's say that you find the expression K3+3 in a floral formula, then the takeaway information for you is that the given calyx has six free sepals and are organised as two separate whorls. Based upon these attributes of the symbols you can get a very good idea about the floral characteristics from any given floral formula. Now that you are equipped with the features of the symbolism of floral formula, let’s understand the floral formula of the family Fabaceae. As a general rule of thumb, it will be beneficial for you to understand that the floral formula is always written in outside-in format i.e. Bracteoles → Perianth or Sepals and Petals → Stamens → Carpels → Ovules.
Floral Formula of Fabaceae
The Fabaceae family is a family of legumes and is a type of angiosperm. They are one of the most common angiosperms and are spread all over the world.
You already know from above the floral formula of Fabaceae family. It is given as - % ⚥
K(5) C1+2+(2) A(9)+1 G1. So, from this formula, the information regarding the floral characteristics of the Fabaceae family is as follows:
%: Zygomorphic plant.
⚥: Bisexual plant.
K(5): Calyx with five sepals which are fused together and hence are called gamosepalous.
C1+2+(2): Corolla with five petals, consisting of a posterior standard, two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil).
A(9)+1: Androecium, in this case, is formed of ten stamens. They are diadelphous i.e. they are joined partially into two structures.
G1: Gynoecium consists of one or more pistils. Here, the pistil consists of one superior ovary, one style, and a single carpel.
Floral Diagram of Fabaceae Family
Based upon the floral formula of Fabaceae family, the floral diagram of Fabaceae is given below:
When you go through the floral characters which are clearly demonstrated by the floral formula of Fabaceae, and then study the floral diagram of Fabaceae, you can clearly see that the diagram is the exact pictorial representation of the formula - the five sepals forming the calyx, the five petals forming the corolla consisting of a posterior standard, two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil), the ten stamens fused into two androecial structures and one superior ovary.
Thus, it is safe to say that one can gather decent amounts of facts from a given floral formula and can be exactly portrayed by the floral diagram. In the given context, the floral formula of family Fabaceae depicts the floral characters in a scientific and factual manner and the floral diagram of Fabaceae is an exact pictorial characterisation of the same.