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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.

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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."— 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 seeds Unpredictable and variable seed crops due to harsh weather conditions Seed maturation periods vary by species- immature and mature seed easily mixed together during collection Western species in remote areas-inaccessible for easy collection Equipment 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. monosperma J. pinchottii J. silicicola J. scopulorum J. virginiana APAT – Università di Siena – USDA Forest Service

5 Distribution of Juniperus in Italy
J. communis J. nana J. hemisphaerica J. oxycedrus J. phoenicea J. thurifera J. sabina APAT – Università di Siena – USDA Forest Service

6 Altitudinal distribution of J. communis and J. oxycedrus
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 J. oxycedrus subsp. macrocarpa J. oxycedrus subsp. oxycedrus J. communis 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
Total Germ Mean Germ Wet wt. Moisture % Seeds/ Mean Viability Species No. Content % Purity kg J. monosperma 3 2 39 . 76 J. pinchottii 21 9 12 13.2 100 30,616 J. scopulorum 113 31 9.2 99.3 60,074 64 J. silicicola 7 10 11.9 97,784 J. virginiana 489 323 41 8.4 95.8 136,651 71

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

11 Male-female ratio of the Italian Junipers
species sites % male % female % not evident J. communis Greve 48.2 51.8 Lecceto 45.8 54.2 Petriolo 51.3 48.7 Montarrenti 41.6 58.4 J. oxycedrus subsp. oxycedrus P.Cavalleggeri 54.8 45.2 Collelungo 18.2 9.1 72.7 Casciano 62.1 37.9 Migliarino 24.0 40.0 36.0 S. Rossore 60.0 J. oxycedrus subsp. macrocarpa Torre Mozza 33.3 66.7 S.Vincenzo 52.0 48.0 8.2 20.4 71.4 25.0 41.7 S.Rossore 14.3 42.9 APAT – Università di Siena – USDA Forest Service

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

13 Mean sugars pollination drop composition in the tree italian Junipers
species Glucose mg/ml Fructose mg/ml Sucrose J. communis _ J. oxycedrus subsp. oxycedrus J. oxycedrus subsp. macrocarpa APAT – Università di Siena – USDA Forest Service

14 Pollination drop retraction at different times
after conspecific pollination 5’ 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 APAT – Università di Siena – USDA Forest Service

17 Micropylar drop volume at different times after pollination in J
Micropylar drop volume at different times after pollination in J. communis and J. oxycedrus subsp. oxycedrus Treatments Micropylar drop volume (mm3 x 10-3) at different times from pollination 0 min. 30 min. 2 h 19 h J. oxycedrus October 2001 Low pollen load 32.2 4.9 0.0 Heavy pollen load 35.2 4.2 1.9 Heavy dead pollen load 29.8 6.4 J. communis pollen (heavy) 29.4 1.6 Charcoal dust 43.3 7.5 7.2 3.9 J. communis February 2002 13.9 1.1 0.7 61.5 9.4 2.1 60.7 0.2 0.1 J. oxycedrus pollen (heavy) 20.5 3.0 Talcum powder 15.1 APAT – Università di Siena – USDA Forest Service

18 Juniperus communis pollen Juniperus oxycedrus pollen
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 Complete retraction  x J. communis Juniperus oxycedrus pollen talcum Partal retraction APAT – Università di Siena – USDA Forest Service

19 Sizes of particles used for artificial pollination experiments
Types of particles Mean size (diameter) J. oxycedrus subsp. oxycedrus pollen 39 µm J. oxycedrus subsp. macrocarpa pollen 40 µm Pyrus communis pollen 62 µm Parietaria diffusa pollen 25 µm Silica gel 1 10-15 µm Silica gel 2 40-63 µm Silica gel 3 µm APAT – Università di Siena – USDA Forest Service

20 Taxon Type of particles
Micropylar drop volume at different times after pollination (mm3 x 10-3) 0 min. 30 min. 2 h 19 h J. oxycedrus subsp. oxycedrus December 2002 Unpollinated 13.9 10.8 13.910.8 28.223.9 Viable pollen 18.78.1 3.72.3 3.22.9 0.00.0 Unviable pollen 16.732.0 0.81.8 0.20.5 Pyrus communis pollen 14.322.8 12.723.0 12.123.2 10.015.2 Silica 1 110.6169.7 80.7120.8 77.5122.5 73.2124.4 Silica 2 65.972.5 38.338.7 40.137.8 31.628.8 Silica 3 10.16.0 9.56.5 9.66.4 20.714.7 J. oxycedrus subsp. macrocarpa unpollinated 53.677.8 54.177.5 72.868.1 23.724.8 7.18.6 1.31.9 0.50.9 22.021.1 2.72.2 2.42.4 2.42.5 40.246.4 30.533.7 21.134.5 13.936.4 Parietaria diffusa pollen 12.010.4 11.510.8 Silica gel 1 83.190.2 29.546.8 48.246.8 85.784.3 Silica gel 2 40.447.5 28.339.3 26.739.5 33.377.9 Silica gel 3 22.418.1 13.915.5 11.216.2 20.928.6

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

22 CONCLUSIONS This research confirms a low germination rate of junipers seeds independently of the species and the environments where they live. The pollination drop system is a weak point in the reproductive cycle because easily deceived by: heterospecific pollen its unviable pollen atmospheric dust increased during the last decades Gymnosperms with pollination drops seem not very well fitted with the actual environment. 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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