finding the fountain of youth
“Delaying the inevitable
onset of senescence slows the
plant’s urgency to complete
its life cycle."
Plants can use a variety of means
to avoid, survive or function in
drought stress. For example, annuals
can mature quickly in a fast-paced,
shortened life cycle that becomes
compressed. High rates of growth
during the early warm season may
allow them to avoid drought entirely.
Stomata may close tightly to reduce
evaporative water loss, which increases
root growth in search of moisture.
Decreasing the size of the canopy
leaf structure reduces growth of new,
above-ground shoots and this slows the
increasing demand for water. These
happenstances, however, will accelerate
leaf and plant senescence.
In most plants under drought
stress, the xylem pathways leading
to fruit development will close by
the fruit’s half-life. This is thought to
protect the developing seeds from the
damaging effects of drought. However,
if xylem function decreases ahead of
this time period, the result is fruits
that are left with a meager supply of
nutrients like calcium and boron that
are commonly transported only in the
transpiration stream. The blackened,
shriveled and splitting distal ends of
tomato fruit are prime examples of
plants left without adequate xylem
distribution pathways.
Limiting Exposure
to Ethylene Gas
Ethylene gas is a significant natural
plant growth hormone that can
shorten the growth of plants. It is used
in agriculture to enhance and force
the ripening of fruits and certain
vegetables. It operates at low parts
per million trace levels during the
life of the plant. Ethylene promotes
the ripening of fruit, the timing of
flowering and the shedding of leaves
as well as the senescence of vegetative
tissues. The production of ethylene
gas in plants can also be induced
by a large range of factors, from
temperature extremes to external
wounding and other environmental
stresses, including excessive wind
damage. Compost piles produce
ethylene and should be located at
a distance from tender crops so as
not to encourage the early onset of
senescence. Limiting exposure to the
gas helps ensure the life of the plant
is prolonged.
Every plant’s challenge is to complete its life cycle while fully achieving the future
vitality and vigor of its offspring. For the grower, the challenge is to extend the
effective growth curve of the plant. Delaying the inevitable onset of senescence
slows the plant’s urgency to complete its life cycle. Growers who employ these control factors and harmonize the growth environment of the plant are well on their
way to achieving maximum yields.
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Maximum Yield USA | January 2015