iii. Flashcards
sapwood
living xylem, typically from the most-recent few years of the tree’s growth.
living xylem
transports water from the soil up to the leaves
the more leaves that a tree has …
the more sapwood it needs to get water to them
The xylem in
sapwood is ____ and so ____
living; requires energy from maintenance respiration to keep it alive
heartwood
older, dead xylem that had been sapwood when it was first created
waterproof because of being filled with secondary substances
when the tree turned old sapwood into heartwood
the sapwood had its nutrient
reserves removed, and had secondary substances added that reduce the chance of it
decaying.
secondary substances
tyloses, resins and dyes
tyloses
deformed cells that fill vessels
a tree does not need …
heartwood to be able to survive, because it is no longer functional
hollow trees can
stand up fine as long as they are in closed-forests
that protect them from high winds
Hollow trees growing in the open …
are more prone being blown down
the hollows in hollow tree-trunks concentrate the wind and that increases the chance they will be blown over
annual tree-rings are typically much clearer in the
heartwood than they are in the
sapwood
photosynthate
chemical energy created from photosynthesis
trees typically allocate the photosynthate in the following ranking of abundance, from
most to least
maintenance respiration
producing leaves and fine roots
flower and seed production
primary growth
secondary growth
maintenance respiration
the greatest amount of photosynthate is used to keep
existing tissues alive
respiration increases as …
temperature increases
producing leaves and fine roots …
to enable continued photosynthesis,
by replacing leaves that fall off seasonally
flower and seed production …
to enable continued survival of a tree’s genes
In years
when many seeds are produced …
trees have lower primary and secondary growth, due
to the energy put into making the seeds
primary growth
elongation of terminal and lateral shoots and woody roots to enable a tree to compete with its neighbors for light and water
secondary growth
new wood to conduct water
trees growing vigorously in high quality habitat …
… have so much photosynthate that
maintenance respiration only takes up 25% of photosynthate, leaving 75% for growth
trees in low quality habitat …
may need 75% of photosynthate for maintenance
respiration and only have 25% left for growth
in very low quality habitats …
the photosynthate may go to maintenance respiration, leaving no energy to grow at all,
which results in those trees having missing rings over their whole surface