1. Chapter 5: Plant growth

2. Meristems
Meristems -regions of active cell division that are sources of indeterminate
plant growth
Apical meristems- primary growth that lengthens roots and stems
Produces primary xylem, phloem and epidermis
Lateral meristems- secondary growth that thickens roots and stems
Vascular cambium –produces secondary xylem and phloem
Cork cambium – produces “secondary epidermis” (bark)
Why is indeterminate growth
so critical to plants??

3. Meristems -primary and secondary growth

4. Xylem –Heartwood vs. sapwood
Heartwood –cavitated, inactive xylem
Provides structural support
Often darker as a result of antimicrobial compounds
Important determinate of wood quality and value
Sapwood- active xylem (1-12 rings)

5. Growth rings Early wood (spring wood) –lighter part of growth ring
larger lumen for greater water transport capacity
Late wood (summer wood) –darker part ring (its what you count)
smaller lumen with greater cell wall thickening to prevent cavitation

6. Growth rings in angiosperms
Ring-porous wood -vessels produced primarily in spring wood
(e.g. oaks, sassafras)
Diffuse-porous wood –vessels produced in spring and summer wood
(e.g. sugar maple, aspen)
Describe a climate scenario where diffuse-porous wood be advantageous

7. Dendrochronology
Science of tree ring dating and climate interpretation

8. Dendrochronology
five of the 28 trees died or were cut earlier than 1847, meaning the pioneers harvested trees both live and dead.
The 1840s were drier than any other decade in this tree-ring history, which spans the years 1702 to 1863,” said BYU professor Matthew Bekker, whose findings are published in the current issue of the academic journal Tree-ring Research. “It was a really rough time to establish a settlement based on irrigated agriculture.”
The tree ring pointed out at the right was grown in 1847, the year the first Mormon settlers arrived in Utah. Bekker's analysis of the ring width indicates 1847 was the 10th driest year in the 162 year tree-ring history.

9. Bark gas exchange
Suberin in cell wall of bark cells blocks oxygen transport
Lenticels – small opening in bark that allows gas exchange
-rapid division and growth of cork cells splits the epidermis

10. World-wide wood consumption
Trends
-1996 world-wide consumption = ~3400 million cubic meters
-55% fuelwood, 45% industrial roundwood = paper, construction wood
-Types of wood usage very different in developed and developing countries

11. Wood products Wood –fuel, paper, construction materials
Wood fluids – latex (rubber), resins, syrup

12. Sustainable forestry
New forestry –management strategies that allow the return of healthy
forests following timber harvest
Selective harvesting- leaving mature trees
Seedling plantings

13. Challenges to sustainable forestry
Nutrient depletion -with the wood you take nutrients from the ecosystem
Seedling establishment is not trivial –competition, herbivory

14. Chapter 5 Homework questions
Explain what indeterminate growth is, how plants do it, and why it is so important to their survival.
(T) Describe the anatomical differences between ring-porous and diffuse-porous wood and explain the climate patterns that would favor each strategy.
Give several examples of wood products important to humans; define sustainable forestry and present two major challenges to forest sustainability following logging.