Effects of Simulated Herbivory on Naupaka (Scaevola taccada) Makamae Kaupu, Samay Primm, and Nicole Yarbrough Professor Mike Ross - Botany 101 Lab Kapi‘olani Community College, Honolulu, HI INTRODUCTION
MATERIALS AND METHODS
Scaevola taccada (Naupaka Kahakai) is an indigenous plant to Hawaiʻi. There are 130 species of Scaevola of which 10 are native to Hawaiʻi. This shrub-like plant has white flowers that produce white fleshy fruits for reproduction. It’s green leaves have white hairs on the epidermis, near axillary buds, and apical meristem regions for protection. The leaves are moderately succulent which help it to tolerate drought, wind, salt spray, and heat. It grows best in coastal environments. Unlike other species of Scaevola, S. taccada produces seeds that can handle floating through salt water currents and will only germinate once they get to fresh water. Scaevola plants have been distributed widely around the world and have become very adaptable. Indigenous people over time have found great uses for several varieties of S. taccada. In South Pacific, people are using S. taccada to treat coughs and TB8. Early Hawaiians used parts of the plant for refreshment on long journeys and to care for cuts, wounds, and skin diseases6. On Cousin Island, S. taccada is aiding habitat restoration efforts for the threatened Seychelles warbler3. This plant is extremely versatile and useful.
Simulated herbivory was tested on the Naupaka Kahakai plant, or Scaevola taccada, by making three groups, each consisting of a sample size of three. Our control group (A) was left untouched, group (B) received three hole punches in exactly half of the plant’s leaves (following Barton 2016 method)1, and group (C) got exactly half of its leaves pulled (following the Raghu et al. 2006 method)7. Each group was treated twice; on January 31st, 2018, the start of the experiment and midway through the experiment on February 28th, 2018. To measure plants we placed a 12 inch plastic ruler horizontally on the rim of the pot and used this as our measurement baseline (0 cm). We placed another ruler atop this baseline, measured to the apical meristem region, and recorded the growth (in cm). To get the most accurate measurement, we repositioned plants observed with curved stems to counter the effects of auxin on stem growth. All nine plants were measured Monday-Friday around 10:40-12:00pm (HST) for 10 weeks. Results were analyzed using a one-way ANOVA with Tukeyʻs Multiple Comparisons in XLSTAT 2014.
Figure 1. S. taccada prior to treatment 01/31/18. (Rows top to bottom: groups (C), (B), and (A).)
Figure 2. Measuring S. taccada (B1).
RESULTS
Effects of Simulated Herbivory on the Growth of Scaevola taccada
Figure 4. Graphical results of simulated herbivory on the growth of S. taccada utilizing methods such as (B) Hole Punch and (C) Leaf Removal. P-value <0.0001
Figure 3. S. taccada at the end of our experiment 04/12/18. (Rows top to bottom: groups (C), (A), and (B).)
CONCLUSION
Based on our data, we concluded that utilizing both simulated herbivory methods, (B) Hole Punch on the leaves or (C) Leaf Removal, did affect the growth of Scaevola taccada. We suspect the results from the use of method (B), reflect damage that was inflicted on the vascular tissues found in the leaves. We presume the results of method (C) are due to changes in the concentration of growth promoting hormones near the apical meristem.
BIBLIOGRAPHY HYPOTHESIS
Simulated herbivory on Scaevola taccada would slow the growth rate due to less surface area of leaves for photosynthesis. Acknowledgments: We would also like to acknowledge Wun Ni Chen for aiding in the collection of growth measurements.
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