29.3.1 Draw and label a diagram showing the structure of a dicotyledonous animal pollinated flower The four kinds of floral organs are the sepals, petals, stamens (male), and carpals (female).Their site of attachment to the stem is the receptacle.
3Sepals and petals are nonreproductive organs. Sepals, which enclose and protect the floral bud before it opens, are usually green and more leaflike in appearance.In many angiosperms, the petals are brightly colored and advertise the flower to insects and other pollinators.
4Stamens and carpels are the male and female reproductive organs, respectively. A stamen consists of a stalk (the filament) and a terminal anther within which are pollen sacs.The pollen sacs produce pollen.Pollen grains contain sperm cells within them.A carpel has an ovary at the base and a slender neck, the style.At the top of the style is a sticky structure called the stigma that serves as a landing platform for pollen.Within the ovary are one or more ovules.Some flowers have a single carpel, in others, several carpels are fused into a single structure, producing an ovary with two or more chambers.
6A monoecious plant has staminate and carpellate flowers at separate locations on the same individual plant.For example, maize and other corn varieties have ears derived from clusters of carpellate flowers, while the tassels consist of staminate flowers.A dioecious species has staminate flowers and carpellate flowers on separate plants.For example, date palms have carpellate individuals that produce dates and staminate individuals that produce pollen.
7In angiosperms, the sporophyte is the dominant generation, the plant we see. Over the course of seed plant evolution, gametophytes became reduced in size and dependent on their sporophyte parents.Angiosperm gametophytes consist of only a few cells.Sporophyte = 2nGametophyte = nSporophytes make spores (which then turn into gametophytes)Gametophytes make gametes (sperm and egg cells, which upon fertilization make sporophytes)
9The Flower and its leaves/stems comprise the sporophyte generation. The stamens and carpels of flowers contain sporangia, within which the spores and then gametophytes develop.The male gametophytes are sperm-producing structures called pollen grains, which form within the pollen sacs of anthers.The female gametophytes are egg-producing structures called embryo sacs, which form within the ovules in ovaries.
119.3.2 Distinguish between pollination, fertilization, and seed dispersal Pollination is the process that places a pollen grain (containing sperm) onto the female stigma (sticky end of the style).The first step in reproductionFlowers attract insects or bees for pollination, or they might rely on wind
12FertilizationOccurs when the sperm from the pollen grain meets the egg in the ovuleOccurs in 5 steps:Pollen grain produces a pollen tubePollen tube grows down the style of the carpelThe pollen tube produces spermThe pollen tube enters the ovaryThe sperm moves from the tube to combine with the egg, forming a diploid zygote.
14Seed DispersalOnce the zygote has formed, a seed will develop from it.The seed is a protective structure for the embryoSeeds may be dispersed by animals (eating fruit and defecating), wind, and/or gravity.Once the seed is on the ground and it is in favorable conditions, it will germinate.
159.3.3 Draw and label a diagram showing the external and internal structure of a named dicot seed. This is a broad beanThe plumule is the shoot apex (embryonic shoot)The radicle is the root apex (embryonic root)
16Seed partsTesta protects the plant embryo and the cotyledon food storesRadicle is the embryonic rootPlumule is the embryonic stemCotyledons contain food store for the seedMicropyle is a hole in the testa ( from pollen tube fertilisation) through which water can enter the seed prior to germinationScar (hilium) is where the ovule was attached to the carpel wall.
179.3.4 Conditions for the germination of a typical seed. Seeds require a combination of factors for their successful germination.oxygen for aerobic respirationwater to rehydrate seed tissues so that they can become metabolically activetemperature for optimal function of enzymesEach seed has its own particular combination of the above three factors.
18Some species require certain events to trigger germination: FireFreezingPassing through the digestive tract of an animalSeed coat erosion (poppy seeds)Washing to remove inhibitors (beans)
199.3.5 Metabolic processes during germination of a starchy seed. The metabolic events of seed germination:Water is absorbed and activates the metabolism of cotyledon cellsb) Water absorption triggers synthesis of gibberellin which is a plant growth hormone that triggers the production of the enzyme amylaseAmylase converts food reserves (starch) from cotyledons into maltose, which is then made into glucose for energySome glucose is made into cellulose for cell walls
209.3.6 Control of FloweringThere are many environmental cues that affect flowering however the photoperiod is the most reliable indicator on 'time' of year (season)The photoperiod is the relative lengths of day and night (which changes with the seasons)Plants must flower when their pollinators are present, so by using light as an indicator of season, plants can tell what time of year it is and thus when pollinators will be present
219.3.6 Control of flowering in long day and short day plants Short day plants (SDP) typically flower in the spring or autumn when the length of day is short. Examples: poinsettieas and astersLong day plants (LDP) typically flower during the summer months of longer photoperiod. Examples: lettuce and radishes
22Night Length is what really matters SDP have a critical long night. That the length of night has to exceed a particular length before there will be flowering.LDP have a critical short night. That the length of night must be shorter than a critical length before there will be flowering.
23Flowering in SDP:Short day plants flower when the night period is long.In day light or red light, Phytochrome Red (Pr) is converted to Phytochrome Far Red (Pfr). The conversion actually only requires a brief exposure to white or red light.In the dark, Pfr is slowly converted back to Pr. A long night means that there is a long time for the conversion.Under short day conditions (long night) at the end of the night period the concentration of Pfr is low.In SDP, low Pfr concentration is the trigger for flowering.
24Flowering in LDP:Long day plants flower when the night period is short.In day light (white or red) the Pr is converted to Pfr.During periods when the day light period is long but critically the dark period is short, Pfr does not have long to breakdown in the dark. Consequently there remains a higher concentration of Pfr.In LDP, high Pfr concentration is the trigger to flowering.
25Conversion of Pfr to Pr is slow during the night