The Flower, the Seed, the Embryo and the Fruit

Lab 11 The flower, the seed, the embryo and the fruit Prepared slides 1) Dicot and Monocot flower bud, cross sections 2) Dicot flower bud Longitudinal section 3) Lilium mature anther Transverse section 4) Lilium ovary general structure 5) Capsella mature embryo L.S 6) Corn grain L.S Fresh specimens: 1-Different monocot and dicot flowers. 2-Presoaked monocot and dicot seeds 3- Different fruits 1 Lab 11 The flower, the seed, the embryo and the fruit The flower: -it is an assemblage of sterile and fertile organs (parts) borne on an axis (receptacle) -the sterile parts are sepals (collectively called calyx) and petals (collectively called corolla) *Resemble leaves in their internal structure, consists of ground parenchyma, branched vascular bundles and epidermis with stomata and trichomes * green sepals contain chloroplast, where as colored petals contain chromoplasts -corolla and calyx together are called perianth - the fertile parts (reproductive organs) of the flower are stamens and carpels * the stamen consists of anthers divided into pollen sacs (each with a number of pollen grains) borne on a thin stalk called filament (made up of parenchyma surrounding the vascular bundle * epidermis is present in both the anther and filament, stomata may present * The anther wall is made of three types of cells (epidermis, endothecium and tapetum (innermost)) - the pollen grain wall consists of an exine and intine , apertures or pores are thin –walled areas in the exine, through which pollen tubes emerge * the pollen grain contains two nuclei, the generative which gives two male (sperm) nuclei and vegetative nuclei which gives the pollen tube - the carpel could be one or more, if two or more carpels are present, they may be free from one another (each carpel = simple pistil) or may be united (compound pistil) * the carpel is differentiated into the lower fertile part, the ovary, the style (could be hollow or solid) and the upper region of the style (stigma) * within the ovary , there are 1) ovary wall (made of parenchyma with vascular bundles, tannin and crystals may be present, the outer layer is epidermis) 2) the locule or cavity and the ovule bearing region-meristematic tissue-(placenta) 2 Exercise 1: study the following prepared slides to recognize parts of the flower and the histology of these parts 1)Dicot and Monocot flower bud, cross sections 2)Dicot flower bud Longitudinal section 3)Lilium mature anther Transverse section 4)Lilium ovary general structure Exercise 2: in a visit to the botanic garden collect different types of flowers, make a cross section in some and a longitudinal section in others and try to identify parts of the flower and try to differentiate between monocot flower and dicot flower. Also try to determine if the flower is perfect or imperfect, the position of the ovary (superior ovary (hypogynous flower) or inferior ovary(epigynous flower) Exercise 3: take an anther of a flower and rub on a clean slide then make a wet-mount slide, you can stain using safranin, try to identify pollen grains 3 The seed and Embryo: - the seed is a mature ovule containing an embryo and sometimes endosperm, it is surrounded by seed coat Suspensor cell Radicle Cotyledons Plumule Capsella fruit Exercise 4: Examine the following prepared slides: 5) Capsella mature embryo L.S 6) Corn grain L.S 4 -Notice the pericarp in capsella (fruit is silicle), parts of dicot embryo (cotyledons, hypocotyl, plumule, radicle) endosperm, suspensor cell and seed coat -Also notice the structure of corn grain (caryopsis: fruit of corn, in which the pericarp fuses with the seed) notice parts of the embryo, endosperm and seed coat - differentiate between monocot embryo and dicot one Exercise 5: study fresh specimens of presoaked monocot seed and dicot seed and recognize parts of the embryo, compare between monocot and dicot seeds. The fruit: -is a mature ovary, it may have other floral parts fused to it , including the receptacle and calyx - the wall of the fruit (pericarp) is made of three layers (endocarp, mesocarp and exocarp) -the classification of fruits into types is closely related to ovary structure and development Exercise 6 : make a transverse section in different fruits and try to recognize layers of the fruit (exocarp, mesocarp and endocarp), notice the placenta. 5