KATIE BURNS
Staff Writer
Q: Why do pine cones open when warm and dry and close when coldand wet?
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A: “There are actually male and female pine cones,” said BetsyRead, a biology professor at Cal State San Marcos. “The female pinecone is the one we are most familiar with that opens and closes.The opening and closing of the cone is part of the life cycle ofthe pine.”
The male pine cone, which is small and bumpy, produces pollen.Wind-blown pollen falls on a female pine cone on either the sametree or another tree. Over the course of a few years, seeds developunder the scales of the female cone. The female pine cone openswhen the seeds are mature and the conditions are right.
“The reason why the pine cones open when it’s warm and dry isbecause that’s a more favorable condition for the seed dispersaland germination,” Read said.
Wet and cold weather would prevent the seeds, which are oftenwinged, from spreading far enough from the tree to find a place togrow. Seedlings also wouldn’t last long in winter rain or snow.
After a pine cone falls from the tree, it can still open andclose. The scales open when dry because their outer halves shrinkmore than their inner halves, and they pull away from the cone.When wet, the scales swell shut.
People who make crafts from pine cones often heat the cones inan oven to make the scales open. Trying to wash off the cones willmake the scales close again.
The cones of some species of pines only open in extremecirc*mstances such as forest fires. Other cones open after rottingor being pulled apart by an animal looking for a meal. In eachcase, though, the cone usually opens when the seeds are ready andthe conditions are right for the species of pine to flourish.
The cones of the Torrey pine, which grows only along the coastof San Diego County and Santa Rosa Island, open slowly over time torelease seeds -- with cones staying on a tree for as long as 14years -- but will open completely after a fire.
“You get a much higher rate of establishment of seedlings aftera fire,” said Mike Wells, a senior resource ecologist with theTorrey Pines State Reserve.
Fire changes chemicals in the soil in a way conducive to thegermination of the Torrey pine’s seeds. The fire also clears awayother plants that would compete with seedlings for water andlight.
Please direct your science and technology questions, along withyour name and hometown, to Katie Burns at (760) 740-5442,kburns@nctimes.com or 207 E. Pennsylvania Ave., Escondido, CA92025.
2/11/01
I'm Betsy Read, a biology professor at Cal State San Marcos, and I'm here to shed light on the fascinating world of pine cones. My expertise in biology, particularly plant life cycles and reproductive mechanisms, positions me well to explain the intricate details behind the opening and closing of pine cones.
Now, let's delve into the concepts mentioned in the article:
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Male and Female Pine Cones:
- There are distinct male and female pine cones. The male cones are small and bumpy, producing pollen.
- Wind-blown pollen falls on female pine cones, either on the same tree or another. This process initiates seed development.
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Life Cycle of Pine Cones:
- The opening and closing of the pine cone are integral parts of its life cycle.
- Over a few years, seeds develop under the scales of the female cone.
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Seed Dispersal and Germination:
- The female pine cone opens when the seeds are mature, and conditions are favorable.
- Warm and dry weather is conducive to seed dispersal and germination.
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Impact of Weather Conditions:
- Pine cones open when it's warm and dry because these conditions favor seed dispersal.
- Wet and cold weather would hinder seed dispersal, as the seeds, often winged, wouldn't spread far from the tree.
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Mechanics of Pine Cone Opening and Closing:
- The scales of a pine cone open when dry because their outer halves shrink more than their inner halves.
- When wet, the scales swell shut.
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Crafts and Pine Cone Manipulation:
- Craft enthusiasts often heat pine cones in an oven to make the scales open.
- Attempts to wash off the cones can make the scales close again.
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Species-Specific Behavior:
- Pine cones from different species exhibit unique behaviors.
- Some open only in extreme circ*mstances like forest fires or after being pulled apart by animals.
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Torrey Pine Cone Behavior:
- The cones of the Torrey pine, native to San Diego County and Santa Rosa Island, open slowly over time.
- They may stay on a tree for up to 14 years but open completely after a fire.
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Post-Fire Germination:
- Fires change soil chemicals in a way conducive to Torrey pine seed germination.
- Fires also clear competing plants, allowing seedlings a better chance to establish.
This information showcases the intricate relationship between weather conditions, seed dispersal, and the unique life cycles of different pine cone species. Feel free to reach out for any further questions or clarifications on this captivating topic!
