Pollen vs Nectar
Flower is a highly specialized reproductive shoot. A typical flower has 4 whorls, one after the other, on a stalk. The stalk can be short or long. The two lower whorls are not directly involved in reproduction. Therefore, they are called accessory whorls. Upper two whorls are directly involved in reproduction. Therefore, they are called reproductive whorls. The reproductive whorl is made up of microsporophylls and megasporophylls. Microsporophylls are called stamens and megasporophylls are called carpels in anthophytes/ angiosperms. Some flowers have both stamens and carpels in the same flower and some flowers possess either carpels or stamens. Third whorl is known as the androecium, which is the male whorl. Fourth whorl is known as the gynoecium, which is the female part of the flower. Reproductive structures give rise to megaspores and microspores or pollens. A main way to disperse microspores or pollens is by insects. In order to attract insects, nectar is very useful.
Male spores are called microspores. Micro spores are also called pollen grains. In flowering plants, microspores are found inside the pollen sac or the microsporangium. Microspores are very small, minute structures. They are almost like dust particles. Each microspore has one cell and two coats. Outermost coat is the extine, and the inner one is the intine. Extine is a tough, cutinized layer. Often it contains spinous outgrowths. Sometimes it can be smooth, as well. The intine is smooth, and it is very thin. It is mainly made up of cellulose. The extine contains one or more thin places known as the germ pores through which the intine grows out to form the pollen tube. The pollen tube elongates through the gynoecium tissues carrying two male gametes in it. Pollen tube grows down and enters the ovule through the micropyle. Then the apex of the pollen tube degrades and the two male nuclei are released in to the ovule. The double fertilization takes place by the fusion of the one male nucleus with the egg cell nucleus, giving rise to the diploid zygote and fusion of the other male nucleus with the diploid secondary nucleus, giving rise to the triploid primary endosperm nucleus.
Nectar is a useful secretion by special glands or organs called the nectarines of the flower. The nectarines are found on flowers and vegetative parts. Floral nectarines can be found in different positions on the flower. The nectar secreting tissue of the nectar is found in the epidermis. Secretary cells possess a very dense cytoplasm. They may be elongated cells like palisade cells. The nectar is covered with a cuticle. Vascular tissues are closely associated with nectarines. Sugar of the nectarines is derived from the phloem. Nectar can be excreted through the cell wall and the ruptured cuticle or sometimes through stomata.
What is the difference between Pollen and Nectar?
• Pollens are haploid cells where as nectar is just a secretion by cells.
• Pollens are involved in sexual reproduction, but nectar is not involved in reproduction.
• Pollens are formed from the microspore mother cells, and nectar is secreted by secretory tissues in nectaries.