Tree Physiology

1. AG-FS-4 The student will be able to identify trees and explain their environmental and economic value. b. Describe the physiological processes of tree growth. Tree Physiology

2. Diameter growth • When a ring of many cells of xylem is laid down by a division of the cambium layer • Rate of growth dependent on may factors such as • Species • Spacing • Overabundant rainfall or drought years • Natural disasters like fire or insects • Site quality • Spring wood is lighter in color with thin-walled cells • Summer wood has heavier cells walls and darker in color • Alternate between spring and summer wood causes annual ring formation How does a tree grow?

3. Height growth • Occurs by elongation from the terminal bud • General height growth completed by the end of June • All cell division for the next year’s growth is completed in the bud by this time • The next season’s growth takes place mostly by elongation of bud cells formed in the previous year

4. 3 main methods of reproduction • Seeds • Sprouts • Suckers • Broad-leaf trees sprout profusely from the stump while needle-leaf tree do not • Eastern cottonwood and black locust send up suckers from underground roots • Most trees reproduce by seeds How do Trees reproduce?

5. 2 main types of seeds • Monocots- have only one seed leaf or cotyledon • Dicots- have two seed leaves or cotyledons • Seed coat protects the embryo or young plant • Endosperm serves as food for the embryo Seed production

6. Sexual parts of flower • Stamen- male part • Anther- produces pollen • Filament- stalk that supports the anther • Pistil- female part • Ovary- enlarged portion at the base of the pistil • Stigma- top of pistil that is sticky to catch pollen • Style- tube through which a grain of pollen grows downward to reach the ovules in the ovary that turn into seeds Flowers

7. Parts of the flower • Sepals- caylx, green leaves underneath the flower • Petals- corolla, attract pollinators • Pistils • Stamens • Incomplete flowers- missing calyx, corolla, stamen or pistil • Complete flowers- have all four parts • Monoecious- male and female flower parts occur in separate flowers on same tree • Dioecious- male and female flowers occur on separate trees

8. Different from hardwoods • Ovules are naked on the cone scales and are not enclosed in ovary • Male cones • In spring, pine produces clusters of staminate pollen-bearing cones or sacs • When ripe, the sacs disperse their pollen and fall to the ground Conifer Reproduction

9. Female cones • produced at the same time and located in greater numbers on the outside of the crown • At pollination time, cone scales spread apart so that pollen grains can reach the stigma • After pollination, pollen grains develop a tube which grows slowly toward the ovule • Takes about a year • Once fertilized, cone grows rapidly with its developing seeds • Takes 2 years for seed to mature • When ripe, the cone dries out, the scales come apart, and the winged seeds are dispersed by the wind • About 85% of the seed fall within 125 feet of the tree producing the seed