SEEDS, TISSUES, ORGAN MODIFICATIONS 91.4 – 91.7 SEEDS, TISSUES, ORGAN MODIFICATIONS

SEEDED VASCULAR PLANTS GYMNOSPERMS – SEEDS THAT DO NOT DEVELOP WITHIN AN ENCLOSED STRUCTURE (EVERGREENS) ANGIOSPERMS – SEEDS THAT DEVELOP WITHIN A PROTECTIVE STRUCTURE (FLOWERING PLANTS) 3 BASIC TISSUE TYPES 1) DERMAL –OUTER PROTECTIVE COVERING (ARIL) TO PREVENT WATER LOSS & PROTECT AGAINST PHYSICAL AGENTS & PATHOGENIC ORGANISMS

2) GROUND – CONSISTS MOSTLY OF THIN- WALLED CELLS THAT FUNCTION IN STORAGE, PHOTOSYNTHESIS, SUPPORT, AND SECRETION 3) VASCULAR - XYLEM & PLOEM CARRY OUT CONDUCTION OF WATER, MINERALS, NUTRIENTS, & GIVES SUPPORT

4) ALL 3 TYPES OF TISSUE ARE DERIVED FROM MERISTEMATIC TISSUE CALLED INITIALS & ONCE DIFFERENTIATED, THEY ARE CALLED DERIVATIVES

PLANT ORGAN MODIFICATION

STORAGE ROOTS

BULBS – STEMS GROW UNDERGROUND VERTICALLY CONSISTING OF ENLARGED BASES OF LEAVES (ONION) TENDRILS

STEM TUBERS –MODIFIED STEMS FOR FOOD STORAGE & CAN FORM ROOTS BY BUDDING OFF STEM

LEAF MODIFICATIONS spines

MERISTEM

AUXINS & PHOTOTROPISM

Phytochrome is a photoreceptor, a pigment that plants use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum. Many flowering plants use it to regulate the time of flowering based on the length of day and night (photoperiodism) and to set circadian rhythms. It also regulates other responses including the germination of seeds, elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings. It is found in the leaves of most plants. Biochemically, phytochrome is a protein with a bilin chromophore.