Download Compound bud - Oklahoma Pecan Managment

Botany
Michael Smith
Dept. of Horticulture & L.A.
Oklahoma State University
Some Commonly Used Terms
Node
Primary bud
Secondary bud
Tertiary bud not visible
in this picture
• Node – The location of the
buds on the shoot
• Internode – The portion of the
shoot between the nodes
• Primary bud – The most
dominate bud at a node
• Secondary bud – The second
most dominate bud at a node
• Tertiary bud – The third bud at
a node.
Pecans have 3 to 4 buds at each
node. Branches older than 1
year only have secondary and
tertiary buds. All primary buds
grow the 1st year.
• Mixed bud – both vegetative
(shoot & leaf) and reproductive
Terminal mixed bud
parts (female flower) in the bud
– Terminal mixed buds frequently
abort, leaving a lateral primary
compound bud as the distal bud
(most terminal).
• Compound bud – contains
multiple buds. A pecan compound
bud contains:
– 2 catkin buds
– Central mixed bud with 2 catkin
groups, shoot, leaves and female
flowers
Primary compound bud
• Typically 1 to 3 distal primary buds
develop shoots and catkins. The
other primary buds initiate growth
but the shoot aborts and the
catkins continue to develop.
• Secondary buds remain dormant
unless the primary bud is killed.
Secondary compound bud
Outer bud
scale
Pecan compound bud
Central
bud scales
Apex
Leaf
primordia
Inner
catkin
bud scales
Catkin
Shoot, leaves, and
maybe female flower
Catkin – The Male Flower
• Many catkins are produced
from a single bud.
• Most of the primary buds on a
1-year-old branch produce
catkins.
• Pecan pollen is disseminated to
the female flowers by wind.
• One medium size pecan tree
can produce enough pollen to
pollinate every pecan tree in
the world. However, because
pollen distribution is at random
in the wind, a super abundance
of pollen is needed to ensure
adequate pollination.
Pollen shedding and pistil
receptivity of selected cultivars
1
May
30
Burkett
Stuart
Squirrel
Western
Pollen shed
Female
receptive
Pecans require cross
pollination by a compatible
cultivar. They will not
effectively self pollinate.
Pollen shedding times for
suggested cultivars are listed
in a Fact Sheet <LINK>.
• Induction – Stimulus causing a bud to
change from vegetative to reproductive
• Differentiation – Visible evidence
(microscopic) of reproductive tissue
development
Below, female flower
differentiation, about early
April, just before budbreak
Below, female flowers just
before pollination
Above, early female
flower differentiation,
about mid February
Fruit Development - Nut
•
•
Fruit cluster – Fruit are borne terminally on
current season’s growth that arises from
buds on 1-year-old branches.
•
•
•
Water stage, the kernel is ≈ ½ expanded
Fruit grow to full size before the
kernel develops. Nuts attain full
size in late August.
As fruit grows the kernel pushes
down the inside of the nut while in
the water stage (the water is
actually an endosperm without cell
walls).
The endosperm forms cell walls in
late August, called the gel stage.
Next carbohydrates (sucrose) are
translocated to the fruit during late
August through mid to late
October, forming the kernel.
About 70% of the kernel is oil, a
very high energy compound. The
kernel also has starch, sugars,
protein, potassium, vitamin E, and
many other compounds. The oil is
high in unsaturated fatty acids,
and has been shown to reduce
LDL (bad cholesterol) when
included in the diet.
The next slide depicts flower induction, differentiation,
flowering and fruit development in a time series.
• April – Budbreak
• May – Current season catkins are expanding, and at the
same time catkins have began differentiating in the
compound buds for next year.
• June – Female flowers are pollinated, the catkins shed
and fruit begin to develop.
• August – Female flower induction for next years crop
takes place, although female flowers will not begin to
differentiate until mid February. The fruit are nearly full
size and the kernel is in the water stage during this time.
• February – Female flowers begin differentiation, catkins
continue to develop.
• April – Budbreak and the whole process starts again.
Budbreak
Pollination
Catkin
differentiation
for next year,
≈ 3 weeks
after
budbreak
Water stage
Pistillate flower
induction
Shuck split
Defoliation
Type 1 catkins nearly developed,
Type 2 catkins incompletely developed
Pistillate flower differentiation
Amling & Amling, 1983
Type 2 catkins resume development,
Type 1 begins expansion
Bud swell
Summary
• Induction of catkins is within 3 weeks of budbreak,
and female flowers in late July to early Aug.
– The stimulus and hormonal/growth regulator changes associated
with flower induction are unknown.
– Winter stored carbohydrates are positively correlated with
retention and development of female flowers.
• Differentiation of catkins begins about 3 – 4 weeks
after budbreak, and female flowers about bud swell.
• Fruit development reduces return bloom.
– Early fruit maturation promotes return bloom.
– Fruit thinning and/or hedging to control crop load.
• Premature defoliation or reduced leaf function
reduces return bloom.
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Follow a recommended pest management program.
Maintain a balanced nutrition program.
Avoid flooded or water saturated soils during leaf expansion.
Avoid late season drought stress.