Maple Samara Design and Dispersal Introduction

1 1 Maple Samara Design and Dispersal Introduction : Plants have yet to evolve powered flight, but the seeds of various trees have developed a technique of gliding (Alexander, 2002). In order for seeds to glide some sort of wing or lifting surface must be attached to the leaf (Alexander, 2002). Winged seeds are called samaras (Alexander, 2002). Samara refers to the whole structure, consisting of the seed, which contains the plant embryo, and the aerodynamic wing surface (Alexander, 2002). The majority of samaras are the autogyrating type, which include the seeds of Maple , pine, ash, and tulip poplar trees (Alexander, 2002). These move in a helicopter fashion (Alexander, 2002).

2 These samaras are comprised of the wing and seed, in which the seed is located at one tip (Alexander, 2002). The center of gravity of these samaras is located at or near the seed mass (Alexander, 2002). When autogyrating samaras fall to the ground with the seed end downward, the winged end begins to rotate around the seed, creating flight (Alexander, 2002). The ecological roles, and habitats of many Maple species have influenced the evolution of the shape and Design of their samaras. These alterations are specific to the Dispersal needs of each species. Examples of these differences can be seen in Acer pensylvanicum (Striped Maple ), Acer spicatum (Mountain Maple ), Acer campestris (Hedge Maple ), Acer platanoides (Norway Maple ), Acer tartarica (Amur Maple ).

3 Acer pensylvanicum is an understory tree, and is the most-shade tolerant of deciduous trees (Wikipedia, 2010). The Samara of other species are designed to travel away from the understory of the parent in order to receive optimal sunlight (Alexander, 2002). Although, it is possible, that the Striped Maple Samara may not be dependent on this 2 flight factor, due to its shade tolerance. Acer Spicatum is a small deciduous shrub or tree, which is known to be located near streams (Wikipedia, 2010). This habitat is extremely useful for the distribution of its seeds via Samara Dispersal . Acer campestris is an intermediate species in the ecological succession of disturbed areas (Wikipedia, 2010).

4 Hedge Maple has high light requirements during its seed-bearing years (Wikipedia, 2010). In order for Hedge Maple seed to germinate and survive, it is possible that the Samara is designed to carry the seed to a non-shaded area. Acer platanoides are known to not be long-lived, so because of this, the species typically produces a large quantity of viable seeds (Wikipedia, 2010). It is plausible that the Norway Maple s samaras are designed to evenly disperse from one another, because of its large production of seeds. Acer tartarica is known to be an invasive species that is a secondary successive species, so it has the potential to be outcompeted by tertiary successive species (Wikipedia, 2010).

5 To prevent this, Amur Maple species produce abundant seeds, ultimately producing high amounts of samaras. This experiment was comprised of two main objectives. The first objective was to compare Samara wing loading (grams/mm2) and descent time of different Maple species. The natural history of each five Maple species was examined, and predictions dependent on wing loading and Dispersal potential for each species were made. It was hypothesized that there is a difference in Samara decent time and wing loading among Maple species. The second objective of this experiment examined the effect altering the curvature, of Acer platanoides Samara to a straightened edge, would have on its descent time.

6 It was hypothesized that decent time of the samaras with the straightened edge would be lower than the Samara with a curved edge. 3 Materials and Methods: Forty samaras per species (Acer pensylvanicum, Acer spicatum, Acer campestris, Acer platanoides, Acer tartarica, were collected. The wing mass (grams) and area for each of these 40 samaras per species was recorded. The wing area was determined by using MVH Image analysis software. Wing loading (grams/mm2) was then calculated by dividing the mass by the area. Next, forty samaras per species were individually dropped from m in a deserted hallway. The descent time of each Samara was recorded using a stopwatch.)

7 An Analysis of Variance test (ANOVA) was run to examine differences in wing-loading and descent time for the five Maple species. Next, a scatter plot for each species was created that compared the effects of Wing Loading on Descent Time. A regression analysis was then used to find the regression equation for the relationship between Wing Loading and Descent Time. For the further study, the effect of altering the curvature of the Acer platanoides Samara , to a straight line, on descent time was examined. The control group consisted of unaltered Acer platanoides samaras. Each control Samara s mass, wing loading and descent time, and statistical analysis were all used from the same procedures used in the above description.

8 For the experimental group a precise cut was made to each of the forty samaras. A cut was made, using a razor blade, right where the seed s bottom end met the bottom side of the Samara wing to the edge of the Samara . This cut removed the curvature at the bottom of the Samara wing, altering it to a straight edge. For the experimental group, the mass, wing loading, and descent time, and statistical analysis were all used from the same procedures as described above. 4 Results: Part I. 5 6 Table 1. Descent Time and Wing Loading Values of the Five Maple Species A. spicatum A. pensylvanicum A. campestris A. platanoides A.

9 Tartarica Descent Time Mean Wing Loading Mean Table 2. ANOVA Test Based Upon Descent Time of the Five Maple Species Source of Variation SS df MS F P-value F crit Between Groups 4 Within Groups 195 Total 199 7 Table 3. ANOVA Test Based Upon Wing Loading of the Five Maple Species Source of Variation SS df MS F P-value F crit Between Groups 4 Within Groups 180 Total 184 According to Figure 1. as the wing loading of Acer spicatum increased, the decent time decreased. As shown in Table 1. the Acer spicatum had the second highest descent time of the five Maple species.

10 The coefficient of variance were fairly low meaning that there was not much variation in descent time from the mean. Although, as shown in Table 1, the Acer spicatum samaras mean wing loading was the second lowest of the five Maple species. According to Table 1, the standard deviation was fairly low, which indicated that there is not much wing-loading variation in this species. According to Figure 2. as the wing loading of Acer pensylcanicum increased, the descent time increased. As shown in Table 1. the Acer pensylcanicum had the third highest descent time of the five Maple species. Although, as shown in Table 1, the Acer pensylcanicum samaras mean wing loading was the highest of the five Maple species.