Angiosperms

                                                                                                                                                             

I.              General information

                A.            Angiosperms probably arose from gymnosperms

                B.            Important evolutionary advances of angiosperms

                                1.             Vegetative - improved vascular system (vessels & companion cells)

                                2.             Reproductive - flowers

II.            Flower structure and physiology

                A.            Major taxonomic components

                                1.             Symmetry

                                2.             Numbers - sepals, petals, stamens, pistils (stigma, style, & ovary)

                                3.             Free or united sepals & petals

                B.            Phenomena associated with flower induction

                                1.             Photoperiodism

                                                a)             Day-neutral plants - flower independently of day length

                                                b)             Long-day plants - flower in response to short nights (corn, wheat, and clover)

                                                c)             Short-day plants - flower in response to long nights (poinsettia, chrysanthemums, Christmas cactus)

                                2.             Circadian rhythm - biological clock

                                3.             Vernalization - cold treatment

III.           Specific reproductive advances

                A.            Increase in sporophytic generation; less gametophytic

                                1.             When unfertilized, less effort is made towards reproductive structures

                B.            Enclosure of ovules

                                1.             Leaves fold and join at the margins to form carpels

                                2.             Carpel walls (fruit walls) mature into a structure that aids in seed dispersal

                                3.             Protection

                C.            Double fertilization

IV.           Phylogeny (evolution) and classification

                A.            Phylum Magnoliophyta (formerly Anthophyta)

                                1.             Subphylum Monocotyledonae

                                2.             Subphylum Dicotyledonae

                B.            Besseyan System

                                1.             Spiral to whorled flowers

                                2.             Many to few flower parts

                                3.             Hypogyny (Superior Ovary; flower situated sepals, petal, stamens, pistils) to epigyny (parts arise from the ovary (inferior ovary)

                                4.             Regular to irregular flower

                                5.             Three main lines of advance

                                                a)             Magnoliaceae (magnolia) ===> Rosacea (roses) ===> Asteraceae (sunflower)

                                                b)             Magnoliaceae (magnolia) ===> Malvaceae (cotton, okra) ===> Lamiaceae (mints)

                                                c)             Magnoliaceae (magnolia) ===> Lilaceae (lilies) ===> Graminae (grasses)