Seeds to fruit to germination and plant

The process by which pollen (a male haploid gametophyte) is transferred from the anther to the stigma enabling fertilization and reproduction With moisture it will germinate on the stigma allowing the pollen tube to grow to the ovule Two types – self pollination and cross pollination

Called double fertilization as two sperm gametes are involved – one fertilizes the female egg and the other joins the two polar bodies within the ovule of the ovary. Here the fertilized ovaries become seeds The diploid zygote becomes the embryo and the triploid portion, the endosperm. Ovaries now become fruits and are essential in some cases for seed dispersal

The seed is the embryonic plant which along with stored food, is enclosed in a protective coating called the seed coat. Seed plants are very successful in reproducing Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. Seeds are dispersed by many methods – wind, water, digestion, burrs clinging, gravity, seed explosion and by humans

The growth or development of the young plant from a seed It must have the proper amount of moisture – water for rehydration, oxygen for cellular respiration to occur and the proper temperature for several reasons: a. Optimum temperature for enzymes involved in metabolic events b. Many angiosperms need cold weather first followed by warm for germination to occur c. Some need bushfires - blueberries

Seed absorbs water – micropyle Gibberellin – plant growth hormone is produced in the cotyledons These stimulate the production of the digestive enzyme amylase which digests starch to maltose The maltose is transported to the areas of the seedling embryo root and the embryo shoot Maltose gets converted to glucose for cellular respiration or to synthesis the cellulose for strength and growth

Events of the life cycle are timed with seasons Photoperiod refers to the stimulus of length of night and day being used to help plants detect the time of year When flowering is the physiological response to day length, it is called a photoperiodism There are three types of plants: oYJPXP9Qo oYJPXP9Qo Long day plants – flower in spring and early summer – June 21 st is the longest day of the year in the northern hemisphere Short day plants – flower in late summer, autumn or early winter – Dec. 21 st is the shortest day of the year Day-neutral plants will flower when a particular stage of maturity is reached; light doesn’t have an effect

Note what a ‘FLASH’ of light can do to the two types of plants affected by light

Due to the effect that red light can interrupt the flowering of angiosperms in short day plants and influence flowering in long day plants, it has been thought that PHYTOCHROME is the pigment involved in photoperiod. It measures the period of darkness Phytochrome exits as Pr – absorbs red light when inactive and Pfr – absorbs far red light when active Pr to Pfr when red light is absorbed during the day Pfr to Pr when far red light is absorbed during the day.

Long day plants Pfr triggers flowering so enough Pfr will remain after short nights to stimulate flowering Pfr inhibits flowering so after a long night there has been enough time to convert the Pfr to Pr and it will stimulate the flowering. Short day plants The gradual conversion of Pfr to Pr times the dark period