W.S.Department 01 Agriculture

Forest Service General Technical Report SE-18

RECOGNIZINGDEVELOPMENTAL STAGES

1.N SOUTHERNPINE FLOWERS:

The Key to Controlled Pollination

bYDavid L. Bramlettl

andClaude H. O’Gwynn” ’

. *

: ,~ _.. %

‘Project Leader, Southeastern Forest Experiment Station,Macon, Georgia.

“Southern Tree Improvement Manager, WeyerhaeuserCompany, Hot Springs, Arkansas.

January 1980

Southeastern Forest Experiment Station

Asheville, North Carolina

Controlled pollinations are vital in southernpine tree improvement programs. Effectivepollinations depend upon three operations. First,female flowers must be enclosed in isolation bagswhen they are in the proper stage of development.Then, viable pollen must be supplied to the ovuleswhen the female flowers are most receptive.Finally, the developing cones must be protecteduntil maturity.

The first two operations are highly de-pendent on recognition of the developmentalstages of southern pine flowers. Timing of flowerdevelopment varies among species and is highlydependent upon spring temperature. This bookletillustrates the developmental stages described byCumming and Righter. z3 It *also gives the pollina-tion procedures to follow during each stage.

Turnming, W.C., and F.I. Righter. 1948. Methods used tocontrol pollination’of pines in the Sierra Nevada of California. IU.S. Dep. Agric., Circ. 792, 18 p. Washington, D.C.

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STAGE1

The female flower bud ( 9 ) is small and tightlyenclosed within the bud scales. One to severalflower buds may occur in a lateral position on avegetative shoot bud (v). This is a good time toidentify potential branches for pollination, but it isstill too early to bag the flowers. Bagging at thisstage causes female flowers to be receptive beforefresh pollen is available.

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STAGE2

Flower buds have enlarged, but the flowerprimordia are still enclosed within the bud scales.Light-colored scales are noticeable at the tip ofthe bud. Isolation bags should be installed now.

STAGE 3

The flower has begun to emerge through thetop of the scales. Flowers are normally red, pink,or light green. Since flowers may have receivedpollen of unknown origin, it is too late to bag.

STAGE4

The flower has elongated and extends be-yond the bud scales, but the lower one-third toone-half of the flower is still enclosed by the budscales. Delay pollination.

STAGE 4 (late)

The flower has extended almost entirely fromthe bud scales, but the maximum space betweenthe scales has not yet occurred. Some seed can beproduced by pollinating flowers now, but yieldsare increased by delaying until stage 5.

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STAGE 5

The flower has completely emerged from thebud scales. Typically, the bud scales are roll.edback, and the flower scales approach a right anglewith the axis of the conelet. The flower is at itsmaximum receptivity because the opening be-tween the scales and the bracts offers the greatestaccess to pollen. Stage 5 normally lasts from oneto several days. Pollinate at this stage.

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STAGE 5 (cuta)vay)

Pollen is wind-borne to the flower and entersthe space between the scales (S) and bracts (B).Paired ovules (0) are embedded on the uppersurface of each scale. The bracts are attached tothe cone axis and the lower surface of the scales.The polien accumulates around the sticky micro-pyle (M) of the ovule and is transported into thepollen chamber by a pollination droplet.

STAGE 5 (fate)

The female flower remains receptive as longas the space between the scales is large enough forthe passage of pollen. The scales gradually in-crease in size and after one to several days of‘receptivity (depending on the species and ambienttemperature) the opening between the scalesdecreases until completely closed. Flowers maybe pollinated in late stage 5, but seed yields maybe low.

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STAGE6

The flower is no longer receptive because thegrowth of the scales completely closes the open-ings. Pollinations in stage 6 produce no seeds.

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RECOMMENDED PROCEDURESFOR

CONTROLLED POLLINATION

Bag flowers in stage 2 on strong vigorousbranches. Earlier bagging may hasten femaleflower, development resulting in receptivity be-fore fresh pollen is available.

Do not bag flowers that have begun to emergefrom the bud scales (stage 3).

Periodically check flowers for flower receptivity.

When flowers are in stage 4, delay pollination butobserve frequently to determine onset of stage 5.

Inject pollen into bag when most flowers in theisolation bag are in stage 5.

Use pollen of highest viability available.

If stored pollen is used, test its viability beforepollination.

LJse an adequate quantity of pollen per bag (ap-proximately 0.50 crniS per bag).

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Try to achieve a good distribution of pollen withinthe bag. Shake bag after pollinating.

Do not try to pollinate all bags on the same tree onthe same day if flowers are not receptive on somebranches.

If flowers in different stages of development are ina single bag, pollinate a second time when late-developing flowers are receptive.

Delay bag removal until 2 weeks after finalpollination.

Protect conelets with insecticides until conematurity.

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ACKNOWLEDGMENTSDrawings prepared by Mary Wain Ellison,

commercial artist, Macon, Georgia. The drawingswere made from photographs taken by J.G.Hutchinson when he was with the S.outheastemForest Experiment Station, Charlottesville,Virginia. Hutchinson is now with the NorthCentral Forest Experiment Station in St. Paul,Minnesota.

The material in this booklet is adapted fromChapter 10, “Controlled Pollination,” in pol/e~~Matiagement Handbook. E. Carlyle Franklin,Editor. USDA Forest Service.

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