Why do pine cones close when wet

Newcomers' Community. Steemit Feedback. Explore communities…. You will also need the following materials on hand: A variety of opened and closed pine cones 2 large glass beakers or normal glass dishes Water Air Heater Instructions: Fill your glass beakers with water.

Place an already closed pine cone in one dish of water, and an opened one in the other. Connect and switch on the air heater and place a closed pine cone as well as an opened one in front of it.

The scales of seed-bearing pine cones move in response to changes in humidity. Administrator October 17, First Name. Last Name. Email Address. Phone Number. After pinecone A has been in the oven for 45 minutes, with the help of an adult, remove it from the oven. Allow it to cool until you can handle it comfortably. Use your measuring tape to measure the length of pinecones A, B and C. Write down their lengths in the column Final Length. Use your measuring tape to measure the circumference of pinecones A, B and C at their widest points.

For each pinecone, write down their circumferences in the column Final Circumference. Compare the length and circumference of the pinecones for each column. Notice which pinecone had the smallest change. Why do you think some pinecones changed more or less than others? Do you notice any other changes in the pinecones? Do they look different? Extra: After pinecone A is out of the oven, try putting it into the cold water. Remove it after several minutes and measure its length and circumference again.

How does cold water affect the size and shape of the pinecones? Extra: Try the reverse. Take pinecone B from the cold water and place it into the oven to heat up. What kind of impact does the heat have on the chilled pinecone? Is it similar to or different from the pinecone A, which was never in cold water? Extra: Try lowering the temperature of the oven to degrees F and testing the effect on the size and shape of another pinecone. Does it get larger than the one in the degree F oven—or smaller?

Why do you think this happens? Extra: After taking the pinecones out of the oven and measuring, put them in the freezer overnight. When you take them out in the morning, measure their lengths and circumferences again, and compare them with the final measurements. Did the pinecones get larger or smaller?

The passive movement is a common phenomenon in the plant kingdom. Swirling motion of wheat awns 11 , self-burial of Erodium cicutarium seeds 12 , transformation of pollen grain 13 and opening of seed pods 14 are good examples of passive movement in plant.

Then, how can they move? The passive motions in these plants are driven by the humidity water-potential gradient between the cells at the tissue level sclerenchymal tissue and the ambient air These microscopic humidity-induced strains on the cells lead to macroscopic changes This hygromorph is very important for pine cones, because it is related to seed dispersal.

Without hygromorphs, success ratio of the seed dispersal would be lower. Given that appropriate structures and systems are essential for hygromorphs, the structural advantages of pine cones are worth studying. In this study, we investigated the interaction between water and the morphological features of pine cones.

Specifically, the effects of water transport on the positional changes in scales of pine cones were systematically studied. This study provides a better understand of the structural characteristics of pine cones.

The damp pine cones close up their scales to prevent seed from releasing on humid weather 1 Fig. After dipping the pine cones in the water, the trajectories of folded scales were traced at intervals of seconds. The positional variations of distal, middle and proximal scales were traced separately; the results are summarized as a graph Fig.

The displacement vectors that were obtained by applying a particle image velocimetry PIV algorithm to consecutive images also show a similar trend Fig. The overlapped images exhibit the position changes of scales caused by the folding motion. The mean velocity of the distal scales is approximately 1. Based on the result, it is concluded that motion of the pine cones caused by water transport is mainly associated with the morphological changes of the distal scales.

When pine cones get wet, they fold their scales. The folding motions are mainly accentuated at the end of the scales. Temporal variation of the moving velocity at each of the scales was estimated from the displacement vectors Fig. The distal and middle scales have maximum instant velocities of 0.

Meanwhile, the proximal scales maintain their original velocity at 0. The next question to be addressed was the mechanism by which the pine cones are damped. Consecutively captured images represent the pathway of water in pine cones Figs. Water droplets flow toward the center of the pine cones along the slopes of the scales.

Blue arrows indicate the movement of a droplet. The length of the blue arrows represents moving distance from the end of the scale. This length gradually increases with the passage of time. The figure was created by the authors using 3ds Max software Autodesk Inc.

The blue arrows indicate the trajectories of water droplet, where the lengths of each arrow represent moving distance of the droplet. After the droplet reaches the center of the pine cones Fig. A small amount of water spreads to the fibers Figs. Since most water moves into the scales with high priority, the scales are rapidly closed up on rainy days before the whole structure gets damped.

This phenomenon also signifies that small amount of water is required for the scales of pine cones to alter their morphologies. In addition, the slopes of the scales allow for the more efficient collection water toward the center of the pine cones. This is the way the pine cones close their scales rapidly.

The mechanism by which pine cones transport most water to scales remains unclear. The secret of this system is three layer-structure of the main body of pine cones Fig. Brown bract scales and white fibers are of different materials: not only are the colors but the constructions of these layers differentiable.

The bract scales have dense structures with pores of small sized Fig. However, the threads like fibers in the middle layer are tangled up Fig. Thus, the middle layer has relatively large pores.

Detailed 3D structures are shown in Supplementary Video 1 and 2. The inner pine cones consist of three layers and they draw water up independently. White arrows represent the direction of the spreading water. The time of fully damping is different each other. Their different micro-structures seemed to induce independent water uptake. Above-mentioned structures induce two distinct ways of water transport.

When the bract scales and the fibers are dipped in water simultaneously, the amount of water absorbed by these regions is dissimilar, namely the levels of the water rise at different pace; the bract scales and the fibers independently transport water Figs. Firstly, the water is rapidly absorbed in the boundary between bract scales and fibers Fig.

This process can be explained by preferential flow phenomenon; when water is transported through porous media with a small fracture crack , typically through soil, most water passes through the fracture rapidly. Then the water spreads from the boundary lines into bract scales and the fibers Fig.

However, wetting trends obviously differ from each other. The wet surface areas of the bract scales and the fibers sharply increase to After seconds, Simultaneously, the fibers draw water up and approximately However, innermost lignified structure does not begin to pump up water from its bottom boundary until 40 seconds elapses Figs. The average wetting rate of the bract scales and the fibers in the first 20 second-interval are 2.

Within seconds, both the bract scales and the fibers are saturated with an average wetting rate of approximately 0. From this result, the water starts to be spread rapidly into the bract scales and the fibers immediately after it reaches them. Lastly, effects of water in scale were investigated. To track the events that occur in the wet scales, X-ray tomography was utilized for the comparison between the inner structures of dry scales and those of the wet scales Figs.

The scales inside the outer layer have hierarchical structure with three dissimilar sizes of porous morphologies Figs. The cross sectional images were reconstructed for 3-dimensional analysis Figs. The air and wet spaces are clearly discriminated by image contrast. Dark gray air space turned light gray after wetting. White color represents the air space and their volume decrease under wet condition e as compare to dry condition d. This change signifies the volume increase of the scale.

The air space in the fibers perpendicular to red boxes b - c was labeled yellow under dry h and wet i conditions.