Leaves and plant reproduction

Leaves Leaf Structure Petiole: stalk that holds the leaf blade up, contains vascular tissue Blade: two types of tissue Palisade mesophyll: contain many chloroplast, site of most photosynthesis. Spongy mesophyll: irregular, loosely packed cells. O 2, CO 2, and H 2 O move through these spaces.

Gas exchange Transpiration: water evaporating from inside of cell to the outside. Exits out of stomata. Characteristics of leaves. Leaf modifications Thorns Succulents Bracts (poinsettias) Sundews bulbs

Plant Hormones 1.Auxins 1.Produced in apical meristems, buds, young leaves, and other rapidly growing tissue. 2.Stimulates elongation of cells. 3.Causes apical dominance and affects fruit formation. 2.Gibberellins 1.Also causes elongation of cells, artificial gibberellins cause fruit to be larger. 3.Ethylene 1.Causes the ripening of fruit. Black spots on bananas are areas of high concentration. 4.Cytokinins 1.Promote cell division.

Plant responses 1.Nastic responses 1.A plant response that causes movement that is not dependent of the direction of the stimulus. 1.Example leaves opening during the day. 2.Tropic responses: responses to external stimuli. Can be positive or negative 1.Phototropism - light 2. gravitropism - gravity 3.Thigmotropism - touch

Plant reproduction Alternation of generations

Alternation in flowering plants

Flower Organs

Types of fruit Seed dispersal !! Dry fruit.

Modes of pollination 1.Self pollination and cross pollination 2.Animal pollination 3.Wind pollination

Photoperiodism 1.Short day plants 2.Long day plants 3.Day neutral 4.Intermediate day require a certain amount of darkness to bloom. Poinsettia