An ecophysiological study of Drosera indica, a rare carnivorous plant in Taiwan
Date Issued
2015
Date
2015
Author(s)
Huang, Hung-Yi
Abstract
Drosera indica is an annual herb with many glandular trichromes, which could secrete mucus to help capturing small arthropods. Currently in Taiwan island, its populations are only found in the wetland of Lienhwa Temple and maintained by artificial disturbance. There are 3 aspects of this study. (1) To understand life cycle, morphology and anatomy of leaf and root of D. indica, I observed wild populations and made histological section. (2) To investigate whether D. indica uptakes nitrogen from captured prey and to estimate the nitrogen (N) sources, derived from root (Nr) and prey (Np), I analysed stable nitrogen isotopes ratio (δ15N) of D. indica, accompanying plants and potential prey. I also grew D. indica in two environments, control and prey excluded, to examine if Np has beneficial effect on D. indica’s growth and reproduction. (3) I hypothesized that the overgrowth of accompanying plants in the wetland inhibited the population of D. indica. To test the hypothesis, I conducted weeding and weeding then rooting treatments at the habitat then examined the effect of these treatments on the population of D. indica and microclimates. I also studied the effects of light and temperature on seed germination and growth of D. indica to evaluate the underlying mechanisms responsible for the inhibition effect of accompanying plants on the D. indica population. In the wetland, D. indica started germinating in March, flowering in May and continued blooming till October. The height of D. indica was about 15 ~ 50 cm, which was different from previous reports. Its flowers have 3 ~ 4 bifid styles, of similar height and entangling with stamens. Self-pollens might adhere on stigmata due to daily flower movement. There are many long and short stalked secretory glands on leaves. Long stalked secretory glands consist of stalked structure and head glandular. Short stalked secretory glands consist of eight cells. The δ15N of D. indica was significantly higher than that of accompanying plants indicating acquiring N source from prey, which was estimated about 46 ~ 58 % of all N content. The capturing of prey increased leaf [N] and the production of seeds of D. indica. Results from field experiments revealed that pattern of variety of photosynthetic photon flux density (PPFD) and soil temperature differed between control and treated plots, and treated plots grew significantly more D. indica plants. Growth chamber experiments showed that seeds of D. indica could not germinate in dark, and remained dormant at low temperature. D. indica grown in high light environment had highest biomass and produced more seeds; those in medium light elongated and produced less seeds; most of those in low light died before flowering. Consequently, these results suggest that D. indica in wetland might not receive enough light for germination and growth due to overgrowth of accompanying plants. In conclusion, light is an important factor limiting the population growth while soil temperature plays an important role in starting the life cycle of D. indica in wetland.
Subjects
Lienhwa Temple Wetland
carnivorous plant
D. indica
microclimate
nitrogen derived from prey
Type
thesis
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