Different meristems generate new cells for primary and secondary growth • APICAL MERISTEMATIC TISSUES • tips of shoots (terminal buds) • axillary buds and • behind the root cap • account for the primary growth • LATERAL MERISTEMATIC TISSUES • Cork cambium and vascular cambium • - Stems of woody plants • account for secondary growth of stems
The primary growth of a plant adds _____ and secondary growth adds _____. branching ... flowers branching ... girth height ... branching girth ... height height ... girth
Apical meristematic tissues and primary growth What are the differences between the location of the apical meristem in the shoot and in the root?
Primary growth of stems and roots If you insert a nail into the bark of a tree at three foot high, when will it be in two years after the tree grows Two feet higher? Which zone accounts for most of the growth of the root?
Primary growth gives rise to asxillary buds As the apical meristem advances, some of its cells remain behind, and these become new axillary bud meristems Which will give rise to leaves
Think pair and share Secondary xylem and phloem are produced by the _____. a. heartwood b. vascular cambium c. cork cambium d. sapwood e. bark The dry tissue that no longer carries water and solutes is called _____. a. periderm b. heartwood c. bark d. vascular cambium e. sapwood Older roots can become extremely thick and woody as _____ accumulates during secondary growth. a. secondary xylem b. sapwood c. primary phloem d. primary xylem e. secondary phloem
Responses to stimuli Tropisms orient plant growth towards or away from environmental stimuli
Phototropism is the growth of the shoot in response to light The hormones called auxins are involved in Phototropism What happens in a twig if the auxin produced by its apical meristem is conveyed equally down all sides? It will elongate. It will produce a flower. It will branch near its tip. It will bend to one side.
Several major types of hormones found in plants Hormone is a chemical signal produced in one part of the body and transported to other parts, where it acts on target cells to change their function. Each hormone has multiple effects, its effect depends on: its site of action, its concentration, and the developmental stage of the plant. In most situations, no single hormone acts alone. it is more of a balance of several plant hormones, that controls the growth and development of a plant.
Cytokinins and auxins work together Auxin transported down the shoot from the terminal bud Inhibits axillary buds from growing Cytokinins from the roots move into the shoot system signaling axillary buds to grow The interaction of cytokinins and auxin Determines the outcome Application: When gardeners cut the terminal buds of a plant, they are encouraging?
Abscisic acid inhibits many plant processes During a drought, ABA causes change in the shape of the guard cells, so the stomata closes Giberrilins stimulate seed germination ABA inhibits seed germination during winter, freezing temps inactivate ABA in the desert, rainfall inactivates ABA
auxin, auxin, auxin, cytokinin, ethylene, gibberellin, gibberellin, abscisic acid
(b) Grapes from control vine (left) and hormone-treated vine (right) (a) Rosette form (left) and bolting (right) Which hormone was involed in the effect on the plants on the right?
Who produces auxins? And how does it affect fruit development?
Application: Florists spray flowers with cytokinins Why?
Which hormone was used in these experiments? Explain why does each banana vary in ripening?