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WHY REPRODUCTIVE EFFICIENCY IN JUNIPERS IS SO LOW? FACTS AND HYPOTHESIS SEED ECOLOGY 2004 an International Meeting on Seeds and the Environment Rhodes.

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Presentation on theme: "WHY REPRODUCTIVE EFFICIENCY IN JUNIPERS IS SO LOW? FACTS AND HYPOTHESIS SEED ECOLOGY 2004 an International Meeting on Seeds and the Environment Rhodes."— Presentation transcript:

1 WHY REPRODUCTIVE EFFICIENCY IN JUNIPERS IS SO LOW? FACTS AND HYPOTHESIS SEED ECOLOGY 2004 an International Meeting on Seeds and the Environment Rhodes Island, Greece (April 29th - May 4th 2004). Jill Barbour – United States Department of Agriculture - Forest Service - National Tree Seed Laboratory – USA Serena Mugnaini - Massimo Nepi - Ettore Pacini - University of Siena - Department of Environmental Sciences – Italy Beti Piotto - APAT Agency for the protection of the environment and for technical services – Department of Nature Protection – Italy

2 Juniperus Seed Collection Problems Native seed collections contain many empty seedsNative seed collections contain many empty seeds Unpredictable and variable seed crops due to harsh weather conditionsUnpredictable and variable seed crops due to harsh weather conditions Seed maturation periods vary by species- immature and mature seed easily mixed together during collectionSeed maturation periods vary by species- immature and mature seed easily mixed together during collection Western species in remote areas-inaccessible for easy collectionWestern species in remote areas-inaccessible for easy collection Equipment for removal of empty and low vigor seed not affordable by all processorsEquipment for removal of empty and low vigor seed not affordable by all processors APAT – Università di Siena – USDA Forest Service

3 Juniperus Seed Germination Problems Complex dormancies - embryo, endosperm, seedcoat, secondary dormancy Long stratification periods - vary warm and cold cycles Seed viability much greater than germination percentages Germination unpredictable in laboratory and nursery Seed sources may respond differently to stratification treatments due to introgression APAT – Università di Siena – USDA Forest Service

4 US Distribution of Juniperus J. pinchottii J. virginiana J. monosperma J. scopulorum J. silicicola APAT – Università di Siena – USDA Forest Service

5 J. communis J. hemisphaerica J. oxycedrusJ. phoeniceaJ. thuriferaJ. sabina J. nana Distribution of Juniperus in Italy APAT – Università di Siena – USDA Forest Service

6 Altitudinal distribution of J. communis and J. oxycedrus J. oxycedrus subsp. macrocarpa J. oxycedrus subsp. oxycedrus J. communis Collelungo (GR) Torre Mozza (GR) San Vincenzo (LI) Marina di GR (GR) Piana dei Cavalleggeri (GR) Migliarino (PI) S. Rossore (PI) Casciano di Murlo (SI) Petriolo (GR) Fontazzi (SI) Montarrenti (SI) Greve (FI) Lecceto (SI) Monteorgiali (SI) 300m 400m 0m 10m APAT – Università di Siena – USDA Forest Service

7 Juniperus seed structure Outer hard integument Inner papyraceous integument endosperm embryo APAT – Università di Siena – USDA Forest Service

8 Fruit germination in nature APAT – Università di Siena – USDA Forest Service

9 USDA Forest Service National Tree Seed Laboratory Seed Testing Data 1962-2002 TotalGermMean Germ Wet wt. Moisture %Seeds/Mean Viability SpeciesNo. %Content %Puritykg% J. monosperma3239...76 J. pinchottii2191213.210030,616. J. scopulorum11331129.299.360,07464 J. silicicola771011.999.397,784. J. virginiana 489323418.495.8136,65171

10 Collection siteslate 2000-early 2001late 2001-early 2002late 2002 J. communisMontarrenti 1.6 1.5 a 3.3 5.8 a 23.3 13.2 b Petriolo 2.0 2.0 a 0 32.2 13.0 b Greve 1.3 1.5 a 2.7 1.5 a 33.3 13.2 b J. oxycedrus subsp. oxycedrus Collelungo - 36.7 5.8 a - Migliarino - 46.7 15.3 a - P. Cavalleggeri - 50.0 17.3 a - Casciano di M. - 6.7 11.5 b - J. oxycedrus subsp. macrocarpa Marina di GR 66.7 20.8 b - Collelungo - 36.7 5.8 a - Migliarino - 53.3 20.8 a - P. Cavalleggeri - 26.7 11.5 a - After fox ingestion 36.7 25.2 a 33.3 15.2 a - After boar ingestion 26.7 15.3 a 26.7 5.8 a - After badger ingestion - 33.3 20.8 a - Not predated 20.0 26.5 a - - Seed viability at different periods, treatments and sites in the Italian Junipers APAT – Università di Siena – USDA Forest Service

11 Male-female ratio of the Italian Junipers speciessites% male% female% not evident J. communisGreve48.251.80 Lecceto45.854.20 Petriolo51.348.70 Montarrenti41.658.40 J. oxycedrus subsp. oxycedrus P.Cavalleggeri54.845.20 Collelungo18.29.172.7 Casciano62.137.90 Migliarino24.040.036.0 S. Rossore40.060.00 J. oxycedrus subsp. macrocarpa Torre Mozza33.366.70 S.Vincenzo52.048.00 P.Cavalleggeri18.29.172.7 Collelungo8.220.471.4 Migliarino25.033.341.7 S.Rossore14.342.9 APAT – Università di Siena – USDA Forest Service

12 Male (left) and female (right) J. communis cones at pollination. AB APAT – Università di Siena – USDA Forest Service

13 Mean sugars pollination drop composition in the tree italian Junipers speciesGlucose mg/ml Fructose mg/ml Sucrose mg/ml J. communis5.0322526.68465_ J. oxycedrus subsp. oxycedrus4.2059171.219740.49843 J. oxycedrus subsp. macrocarpa3.0313444.884470.34324 APAT – Università di Siena – USDA Forest Service

14 Pollination drop retraction at different times after conspecific pollination 05 12 Experiment performed under a stereo microscope where the pollination drop diameter was measured at different time intervals APAT – Università di Siena – USDA Forest Service

15 J. oxycedrus subsp. oxycedrus female cones with the pollination drops (left) and just after pollination (right) APAT – Università di Siena – USDA Forest Service

16

17 Micropylar drop volume at different times after pollination in J. communis and J. oxycedrus subsp. oxycedrus TreatmentsMicropylar drop volume (mm 3 x 10 -3 ) at different times from pollination 0 min.30 min.2 h19 h J. oxycedrus October 2001 Low pollen load32.24.9 0.0 Heavy pollen load35.24.21.90.0 Heavy dead pollen load29.86.4 1.9 J. communis pollen (heavy)29.44.9 1.6 Charcoal dust43.37.57.23.9 J. communis February 2002 Low pollen load13.91.10.70.0 Heavy pollen load61.59.46.42.1 Heavy dead pollen load60.70.20.10.0 J. oxycedrus pollen (heavy)20.53.01.90.0 Talcum powder61.51.9 15.1 APAT – Università di Siena – USDA Forest Service

18 J. oxycedrus subs. oxycedrus and J. communis retraction with different treatments (october 2001 and february 2002) J. Oxycedrus subsp. oxycedrus No pollination Low pollen load Heavy pollen load dead pollen Juniperus communis pollen charcoal dust No retraction x Partial retraction x Complete retraction xx xx J. communis No pollination Low pollen load Heavy pollen load dead pollen Juniperus oxycedrus pollen talcum No retraction x Partal retraction x Complete retraction xxxx APAT – Università di Siena – USDA Forest Service

19 Sizes of particles used for artificial pollination experiments Types of particlesMean size (diameter) J. oxycedrus subsp. oxycedrus pollen39 µm J. oxycedrus subsp. macrocarpa pollen40 µm Pyrus communis pollen62 µm Parietaria diffusa pollen25 µm Silica gel 110-15 µm Silica gel 240-63 µm Silica gel 363-200 µm APAT – Università di Siena – USDA Forest Service

20 TaxonType of particles Micropylar drop volume at different times after pollination (mm 3 x 10 -3 ) 0 min.30 min.2 h19 h J. oxycedrus subsp. oxycedrus December 2002 Unpollinated 13.9 10.8 28.2 23.9 Viable pollen 18.7 8.13.7 2.33.2 2.90.0 Unviable pollen 16.7 32.00.8 1.80.2 0.50.0 Pyrus communis pollen 14.3 22.812.7 23.012.1 23.210.0 15.2 Silica 1 110.6 169.780.7 120.877.5 122.573.2 124.4 Silica 2 65.9 72.538.3 38.740.1 37.831.6 28.8 Silica 3 10.1 6.09.5 6.59.6 6.420.7 14.7 J. oxycedrus subsp. macrocarpa December 2002 unpollinated 53.6 77.854.1 77.5 72.8 68.1 Viable pollen 23.7 24.87.1 8.61.3 1.90.5 0.9 Unviable pollen 22.0 21.12.7 2.22.4 2.4 2.5 Pyrus communis pollen 40.2 46.430.5 33.721.1 34.513.9 36.4 Parietaria diffusa pollen 12.0 10.4 11.5 10.8 Silica gel 1 83.1 90.229.5 46.848.2 46.885.7 84.3 Silica gel 2 40.4 47.528.3 39.326.7 39.533.3 77.9 Silica gel 3 22.4 18.113.9 15.511.2 16.220.9 28.6

21 J. oxycedrus subsp. oxycedrus micropylar drop retraction after different treatments J. oxycedrus subsp. oxycedrus Viable pollen Unviable pollen Pyrus comm. pollen 62 µm Silica gel 10- 15 µm Silica gel 40- 63 µm Silica gel 63- 200 µm No retraction x x Partial retraction xx Complete retraction xx APAT – Università di Siena – USDA Forest Service

22 CONCLUSIONS 1.This research confirms a low germination rate of junipers seeds independently of the species and the environments where they live. 2.The pollination drop system is a weak point in the reproductive cycle because easily deceived by: a)heterospecific pollen b)its unviable pollen c)atmospheric dust increased during the last decades 3.Gymnosperms with pollination drops seem not very well fitted with the actual environment. 4.Angiosperms with stigmatic pollination are probably better adapted to the present environment, but this must be demonstrated APAT – Università di Siena – USDA Forest Service


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