Flowers are those parts of the plant that are stable in any environment. Hence they are form the important parts as criteria for the purpose of identification and classification of the plants. The flowers are the part which are mainly responsible for reproduction and continuation of the plant species. These flowers arise from the part of the plant known as bracts. The length of the flowers depend on the length of the stalk which is known as Pedicel or Peduncle. It is that part of the flower which attaches it to the plant. The upper part of the pedicel is having a swollen part which is the Thalamus or receptacle. It is this part of the flower which embeds or attaches the other floral parts in it.
BASIC PARTS OF THE FLOWER
The floral parts consists of basic four parts namely Sepal, Petal, Stamen and Carpel.
- The SEPALS are the first part of the flower to grow and protect the flower by covering them during the bud stage. The sepals are the outer most part of the flower which are leaflike and is green in colour.
- The PETALS are bright coloured part of the flower which attract the world towards it. It is the one that attract the agents of pollination like bees, insects, birds, etc also. These petals are together form the COROLLA. The petals vary from size, colour, number, etc and even form layers in some flowers.
- The STAMENS are the Male reproductive part of the flower. It consists of two parts namely stamens and anthers. The stamen is a long cylindrical tube which supports the a sac like part known as the Anthers. The anthers are the parts which consist of the pollen grains. These pollens consist of the male reproductive cells that get either dispersed or pollinated by the relevant agents.
- The fourth part namely the CARPELS are the female reproductive organ of the flower. These carpels consist of a sac like structure known as Ovary. The ovary holds the developing seeds in it. This ovary extends to become the Style which is a tube like structure. The style is the tube which supports a flat surface with a sticky texture. This part or surface is known as Stigma. It is in this part that the pollen grains are received and result in germination.
PARTS OF THE FLOWER
Thus the above four parts cover the different parts namely Peduncle, Pedicel, Receptacle, Calyx or Sepals, Bract, Perianth, Corolla, Filament, Anther, Stigma, Style, Ovary and Ovule. The Peduncle is the stalk from where the branch is connected to the pedicel or stalk of the flower especially in the branched inflorescence. The Pedicel is the stalk of the flower which connects it to the main stem or the peduncle. On top of the pedicel is the Receptacle which is the support for the hole flower. It also houses the ovary and ovule inside it. It is followed by the Sepals or Calyx which is leafy like green structure. In flowers which don’t have sepals will be replaced by Bracts which are at times colourful too. The part that follows the bracts is the perianth and is the part that covers or protects the reproductive parts of the flower.
The perianth consists of petals and sepals or calyx where the petals consist of inner perianth and calyx or sepals are the the outer perianth. The perianth is followed by the remaining parts which forms the male and female reproductive parts named as Androecium and Gynoecium of the flower. The Androecium consists of the Stamens, Anthers and Pollen grains while the Gynoecium consists of Style, Stigma and Ovary. The ovules are present in the ovary that form the seeds for fertilisation.
MACROSCOPICAL CHARACTERS
The macroscopical character of flower includes the different aspects like symmetry, Position of Gynoecium, Arrangement and character of floral parts, Aestivation and placentation. Each character will give a clarity as to which group or species the plant will belong to.
Symmetry
The definition of Floral Symmetry is the ability to divide its perianth into identical or mirror images. Based on this character, it is of 3 types namely:
- Actinomorphic – A character where the perianth can be divided into two equal halves from any angle. For eg. Dattura, Hibiscus
- Zygomorphic – When the flower is divisible into two equal halves only in a particular angle. For eg. Aragvadha or cassia fistula
- Asymmetrical – When the flower is indivisible into two halves from any angle. For eg. Tagara or valeriana.
Position of Gynoecium
The position of the Gynoecium varies with relative position of the other floral parts. This will result in 3 categories namely:
- Hyopgynous – The condition where the petals, sepals and stamens are present below the ovary and ovules. For eg. Hibiscus
- Perigynous – A condition where the petals, sepals and stamens are attached to the margin of Thalamus and the gynoecium is present at the base. For eg. Rose
- Epigynous – This is a condition where the floral parts namely petals, sepals and stamens are present above the ovary. For eg. Cucumber.
Arrangement and character of Floral parts
This part of the information is specifically dealing with the different parts of the flower and their variations. This includes the bracts, Calyx and Corolla
- Bracts – When the flower arise from bracts, then it is said as bracteate flower. When a large bract envelops a whole inflorescence then the bract is a Spathe. When the size of the bract is larger than the flower then it is a Petaloid. Lastly when these bracts are small, dry and scaly, then it is Glumes.
- Calyx – The calyx is the outermost whorl and the sepals are the members of the calyx. When all the sepals are free then it is polysepalous while when they fuse, then it is gamosepalous.
- Corolla – The second whorl of flower is the corolla and it consists of petals as its members. When the petals of free then the condition is Polypetalous while when the petals fuse together, then the condition is gamopetalous.
Aestivation
The arrangement of sepals or petals in a particular pattern within a floral bud is Aestivation. Based on aestivation there are four types of arrangements namely:
- Valvate – An arrangement where the petals of a whorl lie adjacent to the other with one just touching it.
- Twisted – The variety of arrangement where the margin of a petal covers the adjacent petals while the adjacent petal covers its next petal resulting in one over lapping over the other.
- Imbricate – Here a petal in the whorl covers a margin of the adjacent petals while the rest of the petals follow the pattern of ‘twisted’ arrangement.
- Quincuncial – The imbricate aestivation with a slight modification gives rise to Quincuncial aestivation. Here the petals are five out of which two are completely internal and two are external while the remaining petal will have one margin internal and the other external.
Placentation
Attachment of the ovules on Ovule walls with a cushion is the placenta. The pattern of placental arrangement on the walls of the ovary is called as placentation. Commonly there are 6 types of placentation, namely:
- Marginal – The type of placentation which develops along the junction of two fused margin, is the Marginal Placentation.
- Parietal – The arrangement of the ovule where it is a fusion of two carpels, or petals, etc.
- Axilla – As the fusing margins of the carpel takes place and result in an axis at the centre of the ovary. The ovules thus born will be present on this axis. This also results in multiple chambers corresponding to the number ovules.
- Free central – In this type of arrangement, the ovary is single with an axis at its centre. The ovules that form in the ovules are attached to the axis.
- Superficial – The ovules in this variety of placentation attach themselves to the walls of the loculi.
- Basal – The ovary is unilocular and only a single ovule is seen at its base.