Journal of Pharmacognosy and Phytochemistry 2017; 6(3): 304-311 E-ISSN: 2278-4136 P-ISSN: 2349-8234 Pollination and evolution of plant and insect interaction JPP 2017; 6(3): 304-311 Received: 03-03-2017 Accepted: 04-04-2017 Showket A Dar, Gh. I Hassan, Bilal A Padder, Ab R Wani and Sajad H Showket A Dar Parey Sher-e-Kashmir University of Agricultural Science and Technology, Shalimar, Jammu Abstract and Kashmir-India Flowers exploit insects to achieve pollination; at the same time insects exploit flowers for food. Insects and flowers are a partnership. Each insect group has evolved different sets of mouthparts to exploit the Gh. I Hassan food that flowers provide. From the insects' point of view collecting nectar or pollen is rather like fitting Sher-e-Kashmir University of a key into a lock; the mouthparts of each species can only exploit flowers of a certain size and shape. Agricultural Science and This is why, to support insect diversity in our gardens, we need to plant a diversity of suitable flowers. It Technology, Shalimar, Jammu is definitely not a case of 'one size fits all'. While some insects are generalists and can exploit a wide and Kashmir-India range of flowers, others are specialists and are quite particular in their needs. In flowering plants, pollen grains germinate to form pollen tubes that transport male gametes (sperm cells) to the egg cell in the Bilal A Padder embryo sac during sexual reproduction. Pollen tube biology is complex, presenting parallels with axon Sher-e-Kashmir University of guidance and moving cell systems in animals. Pollen tube cells elongate on an active extracellular matrix Agricultural Science and in the style, ultimately guided by embryo sac signals. A recognition system occurs between pollen grains Technology, Shalimar, Jammu and the stigma. Complex mechanisms act to precisely target the sperm cells into the embryo sac. These and Kashmir-India events initiate double fertilization in which the two sperm cells fuse to produce products. Ab R Wani Sher-e-Kashmir University of Keywords: Pollination, Evolution, Reproduction, Double fertilization, Bees Agricultural Science and Technology, Shalimar, Jammu Introduction and Kashmir-India The process by which pollen is transferred to the female reproductive organs of a plant, thereby enabling fertilization to take place is known as pollination. Like Sajad H Parey Sher-e-Kashmir University of all living organisms, seed plants have a single major goal: to pass their genetic information on Agricultural Science and to next generation. The reproductive unit is the seed, and the pollination is a process through Technology, Shalimar, Jammu which it is produced in all spermatophytes. For the process of pollination to be successful, a and Kashmir-India pollen grain produced by the anther, the male part of a flower, must be transferred to a stigma, the female part of the flower, of a plant of the same species. The process is rather different in angiosperms (flowering plants) from what it is in gymnosperms (other seed plants). In angiosperms, after the pollen grain has landed on the stigma, it creates a pollen tube which grows down the style until it reaches the ovary. Sperm cells from the pollen grain then move along the pollen tube enter the egg cell through the micropyle and fertilize it, resulting in the production of a seed. A successful angiosperm pollen grain (gametophyte) containing the male gametes is transported to the stigma, where it germinates and its pollen tube grows down the style to the ovary. Its two gametes travel down the tube to where the gametophyte (s) containing the female gametes are held within the carpel. One nucleus fuses with the polar bodies to produce the endosperm tissues, and the other with the ovule to produce the embryo [1, 2]. Hence the term: "double fertilization". In gymnosperms, the ovule is not contained in a carpel, but exposed on the surface of a dedicated support organ, such as the scale of a cone, so that the penetration of carpel tissue is unnecessary. Details of the process vary according to the division of gymnosperms in question. Two main modes of fertilization are found in gymnosperms. Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gametophytes have sperm that are unable to swim but are conveyed to the egg along a pollen tube. The study of pollination brings together many disciplines, such as botany, horticulture, entomology and ecology. The pollination process as an interaction between flower and pollen vector was first addressed in the 18th century by Christian Konrad Sprengel. It is important in Correspondence horticulture and agriculture, because fruiting is dependent on fertilization: the result of Showket A Dar pollination. The study of pollination by insects is known as anthecology. Sher-e-Kashmir University of Agricultural Science and Process of Pollination Technology, Shalimar, Jammu Pollen germination has three stages; Hydration, Activation and Pollen tube emergence. and Kashmir-India ~ 304 ~ Journal of Pharmacognosy and Phytochemistry Hydration: The pollen grain is severely dehydrated so that takes place when the nucleus of one of the sperm cells enters its mass is reduced enabling it to be more easily transported the egg cell in the mega-gametophyte’s archegonium [5]. from flower to flower. Germination only takes place after In flowering plants, the anthers of the flower produce rehydration, ensuring that premature germination does not microspores by meiosis. These undergo mitosis to form male take place in the anther. Hydration allows the plasma gametophytes, each of which contains two haploid cells. membrane of the pollen grain to reform into its normal bilayer Meanwhile, the ovules produce megaspores by meiosis, organization providing an effective osmotic membrane. The further division of these form the female gametophytes, which interaction between pollen and stigma is the first event in are very strongly reduced, each consisting only of a few cells, plants that initiates the process leading to fertilization. Mature one of which is the egg. When a pollen grain adheres to the pollen grains of angiosperms are always desiccated to some stigma of a carpel it germinates, developing a pollen tube that extent at the time of dispersal. The water content varies grows through the tissues of the style, entering the ovule among different species, with most values ranging from 15 to through the micropyle. When the tube reaches the egg sac, 35% fresh weight. The state of dehydration is associated with two sperm cells pass through it into the female gametophyte an almost inactive metabolism. By contrast, uptake of water and fertilization takes place [4]. allows the development of osmotic pressure and the regaining of an active metabolism. The time needed for rehydration of Abiotic pollination the pollen on the stigma may vary greatly depending on the Hydrophily and anemophily species; for example, 15 min in Arabidopsis thaliana and Abiotic pollination refers to situations where pollination is more than 60 min in Brassica oleracea. mediated without the involvement of other organisms. The most common form of abiotic pollination, anemophily, is Activation: Activation involves the development pollination by wind. Wind pollination is very imprecise, with of actin filaments throughout the cytoplasm of the cell, which a minute proportion of pollen grains landing by chance on a eventually become concentrated at the point from which the suitable receptive stigma, the rest being wasted in the pollen tube will emerge. Hydration and activation continue as environment. This form of pollination is used by grasses, the pollen tube begins to grow [3]. most conifers, and many deciduous trees. Hydrophily is pollination by water, and occurs in aquatic plants which Pollen tube growth: In conifers, the reproductive structures release their pollen directly into the surrounding water. About are borne on cones. The cones are either pollen cones (male) 80% of all plant pollination is biotic [6]. In gymnosperms, or ovulate cones (female), but some species biotic pollination is generally incidental when it occurs, are monoecious and others dioecious. A pollen cone contains though some gymnosperms and their pollinators are mutually hundreds of micro-sporangia carried on (or borne on) adapted for pollination. reproductive structures called sporophylls. Spore mother cells in the micro-sporangia divide by meiosis to form haploid Entomophily microspores that develop further by two mitotic divisions into The best-known examples probably are members of the immature male gametophytes (pollen grains). The four order Cycadales and associated species of beetles. Of the resulting cells consist of a large tube cell that forms the pollen abiotically pollinated species of plant, 98% are anemophilous tube, a generative cell that will produce two sperm by mitosis, and 2% hydrophilous. It is thought that among and two prothallial cells that degenerate. These cells comprise angiosperms, entomophily is the primitive state; this is a much reduced micro-gametophyte, which is contained indicated by the vestigial nectaries in the wind- within the resistant wall of the pollen grain [4, 5]. pollinated Urtica and other plants, and the presence of The pollen grains are dispersed by the wind to the female, fragrances. Of the angiosperms, grasses, sedges, rushes and ovulate cone that is made up of many overlapping scales catkin-bearing plants are in general wind pollinated. Other (sporophylls, megasporophylls), each protecting two ovules, flowering plants are mostly biotic, the pollen being carried by each of which consists of a mega-sporangium (the nucellus) animal vectors. However, a number of plants in multiple wrapped in two layers of tissue, the integument and the families have secondarily adopted wind pollination in contrast cupule, that were derived from highly modified branches of to other members of their groups. Some plants are ancestral gymnosperms. When a pollen grain lands close intermediate between the two pollination methods.