Hachi's posts

★
Some developmental genes for shoot apical meristems and vascular cambium are related

★
Weight carried by the stem activates developmental program for wood formation

★
Older layers of periderm are sloughed off

★
New cork cambium forms to the inside, producing another layer of periderm

★
As stem/root thickens, first cork cambium splits and differentiates into cork cells

★
Lenticels (horizontal slits) - cork cells more spaced out, allow gas exchange thru periderm

★
Periderm = cork cambium + the tissues it produces

★
Produces cork cells that replace the epidermis → deposit waxy, hydrophobic suberin in cell walls and then die → waxy cork layer prevents water loss, physical damage, and pathogen attack

★
Cork cambium - cylinder of meristem in the outer cortex of stems and pericycle in roots

★
Older secondary phloem is sloughed off as circumference increases

★
Sapwood - outer layer of new secondary xylem, transport xylem sap (water/minerals)

★
Heartwood - old secondary xylem, in center of stem/root, darker due to resins that protect it from fungi/insects

★
Only newer layers of secondary xylem and secondary phloem aid in transport

★
Growth ring in cross sections - estimate tree’s age and climate change