stems. so what do we already know????? stems exist for three reasons to produce leaves, branches and...
DESCRIPTION
Stems exist for three reasons To produce leaves, branches and flowers To hold leaves up to the sunlight To transport substances between rootsTRANSCRIPT
STEMS
SO WHAT DO WE ALREADY KNOW?????
Stems exist for three reasonsStems exist for three reasons•To produce leaves, branches and flowers•To hold leaves up to the sunlight•To transport substances between roots
Stem Basics
1. Stems develop from the embryonic hypocotylhypocotyl
2. We call the stem and the leaves the shootshoot
3. Stems can present a variety of forms some typical some not so much. Consider the stem of a carrot. Where is it????
4. Stems contain the apical meristem.apical meristem. What’s that?What’s that?
a) Shoot apical meristem(b) Leaf primordial
(c) Axillary bud primordium(d) leaf
(e) Stem tissue
Growth of StemsIn the spring, the shoot lengthens rapidly
from the elongation of cells below the apex similar to the “extension of a telescope”
Will produce two patterns of growth in stems 1. Apical Dominance- excurrent growth
pattern2. Lack of Apical Dominance- deliquescent
growth pattern
Apical Dominance or Excurrent Growth
AUXIN!
Apical DominanceExcurrent Growth Pattern
Effects of Pruning
Deliquescent Growth
External Stem Features
External Stem Features
How is a stem ‘put together’?
Function of…Function of…
• Cork-• Cortex-• Phloem-• Vascular cambium-• Xylem-• Pith-
DENDROCHRONOLOGY
Dendron= tree+
Chronos= time+
Logos= word= the study of_____________________
DENDROCHRONOLOGY
DEPENDENT ON THE PRINCIPLE OF “UNIFORMITY IN THE ORDER
OF NATURE”OR
The concept that the present is the key to the past.
but it’s a whole lot more than that…
• DENDROARCHAEOLOGY- uses tree rings to date when timber was felled, transported, processed or used for construction of wooden artifacts
• DENDROCLIMATOLOGY-uses tree rings to study climate and reconstruct past climate
• DENDROECOLOGY- uses tree rings to study factors that affect earth’s ecosystems
AND AT LEAST 5 MORE “DENDROS”
SEAHENGE at Holme-next-the-Sea
WHY RINGS???• EARLY IN THE GROWING
SEASON TREES PRODUCE THIN-WALLED CELLS REFERRED TO AS SPRINGWOOD OR EARLYWOOD.
• LATER IN THE GROWING SEASON WHEN CONDITIONS ARE LESS THAN OPTIMUM, TREES PRODUCE THICKER-WALLED CELLS CALLED SUMMERWOOD ORLATEWOOD.
• TOGETHER, THESE MAKE WHAT WE REFER TO AS AN ANNUAL RING.
Factors that affect the appearance of annual rings
include the following.• RAINFALL• PHYSIOLOGY• SLOPE GRADIENT• SUN• WIND • SOIL PROPERTIES• TEMPERATURE • SNOW ACCUMULATION
Annual Rings can be compared and
matched with trees growing in the same geographical zone and under similar climatic
conditions to produce CHRONOLOGIES.
The Increment Borer
CHRONOLOGIES• The Bristlecone Pine
which can live for thousands of years has produced tree ring records that travel 9000 years into the past.
• River Oaks growing near the Main and Rhine Rivers provide records from over 10,000 years ago