Searching for Nature Stories 2016 Parasitism of Cuscuta Chinensis--relationship between dodder ​ ​ and its host Team 7 Po Leung Kuk Centenary Li Shiu Chung Memorial College S5 Lui Ho Kwan S5 Tsang Ho Hin S5 Ho Wing Sze S5 Leung Siu Hang S5 Wong Yuen Ting Supervising Teacher: Lau Kwong Wing Content 1. Abstract 2. Introduction 2.1 Introduction of research topic 2.2 Reason of investigation 2.3 Objectives 2.4 Research questions 2.5 Background information of Cuscuta Chinensis ​ 3. Materials and Methods (Process, equipment, time & venue) 3.1 Working schedule (content of each field trip) 3.2 Materials needed in this project(plant used) ​ 3.3 Dissection of plants 4. Results 4.1 Collected data 4.2 Experiments 5. Discussion 5.1 Discussion on objective 1 5.2 Discussion on objective 2 5.3 Discussion on objective 3 5.4 Limitations 5.5 Improvements 5.6 Possible errors 5.7 Conclusion 6. Bibliography 1.Abstract ➤ ➤ Fig.1 ​Cuscuta Chinensis ​after 4 days germination ​ ​ ​ ​Fig.2 Cuscuta​ Chinensis ​wrapping around its host Cuscuta Chinensis is a species of Cuscuta, which can also be called dodder, ​ has rough seed coat and a protruding hilum as its notable characteristics. Like the other species of dodders, they can be identified by its thin stems appearing leafless, with the leaves reduced to minute scales, and reaching out for a green ​ ​ plant after germination. Though Cuscuta are hemiparasitic, they are more likely to be described as holoparasitic plants since they depend almost entirely on their host plant for water, nutrients, and organic carbon acquisition.1 In this project, our objectives are to investigate the preference of host ​ selection on different types of plant and sugar content, plus dodder’s growing ​ ​ ​ behaviour. Cuscuta Chinensis were grown in this project to carry out several ​ ​ ​ ​ experiments in our school laboratory for research. Also, their growth are recorded by photos and descriptions throughout the whole process. According to the results of the experiments, it was found that dodder would ​ not have a specific target to choose host plants and they prefer plants with higher sugar content as their hosts. Also, dodder can apparently survive for a longer period of time with a host, but ‘fake’ hosts, which are dead plants or non-living objects would not attract them to grow towards to as well as survival time. 1 https://legacy.wlu.ca/page.php?grp_id=2147&p=19554 2.Introduction 2.1 Introduction of research topic ​ Dodders are parasitic plants which do not have any roots, chlorophyll or leaves. Instead of carrying out photosynthesis to support their own living, dodders obtain nutrients from the hosts through parasitism. Otherwise they will die. However, apart from the basic need of survival, there should be several factors that may affect the decision of dodders to host on. In our investigation, we would like to study the growing behaviour of dodder, such as the number of days of survival after germination with or without host, as well as investigating whether types of plant (dicots or monocots) and sugar content of plants would affect dodders’choice of host plant. 2.2 Reason of investigation As dodders are known for damaging the surrounding plants, many countries have laws prohibiting the import of dodders seed. We are interested in the damage that dodders can do to the plants and its growing behavior that force governments in different countries to ban the use of dodders. Therefore, we decide to investigate dodders’ preference on target plant and how does its ‘damaging process’ work. 2.3 Objectives 1.To investigate the preference of dodders’ host selection on different types of ​ ​ ​ ​ ​ plant 2.To investigate dodders’ selection on different sugar contents of plant ​ ​ 3.To investigate the growing behavior of dodders. 2.4 Research questions 1.What factor will affect the hosting merchanism of dodders? 1.1.Is dodders likely to choose monocots or dicots as host? 1.2.Is dodders likely to choose plants with high or low sugar content? 2.How do dodders host on plants? 2.5 Background information of Cuscuta Chinensis ​ The dodders planted for investigation are classified as below: Kingdom: Plantae Phylum: Angiosperms Subphylum: Eudicots Class: Asterids Order: Solanales Family: Convolvulaceae Genus: Cuscuta Species: Chinensis 3.Materials and Methods 3.1 Working Scheldule During the past five months, we have had three field trips to help us conduct our project. Date Venue Objective 18/11/15 Field near our school To find some inspiration for our project, because there are many types of plants in the field. 13/12/15 Tsung Tsai Yuen At the beginning, we would like to investigate lichen, so we went to Tsung Tsai Yuen in Tai Po to collect some samples of lichen. However, considering the slow growing rate of lichens, we gave up the idea after the field trip. 23/2/16 Field near our school There are many different species of plants in that field, so we tried to see if there is any dodders in the area. ➤The field near our school ➤Tsung Tsai Yuen ​ ​ ​ ​ 3.2 Materials needed in this project Plants Dicots: 1.Catharanthus roseus(Rosy periwinkle) ​ ​ 2.Plantago asiatica(Chinese plantain) ​ ​ 3.Gynura cusimbua(Hill Gynura) ​ ​ Monocots: 1.Dracaena sanderiana(Lucky Bamboo) ​ ​ 2.Allium fistulosum(Bunching onion) ​ ​ 3.Chlorophytum comosum(Spider plant) ​ ​ Dodders: Cuscuta Chinensis(Dodders) ​ Gardening equipment Hand trowel Pot Soil 3.3 Dissection Hypothesis We assume that dodders make use of their thin stem and fine sucker to wrap ​ around the stem of the host plant and draw nutrients from them to support their own growth. They are estimated to host on any types of plant and prefer high sugar content plants instead of low sugar content ones. ​ Design of experiment To get a thorough understanding of dodders’ behaviour during parasitism, we observe the dissections of various plants (host plants that have been attacked by dodders)under microscope. To minimize the error due to positional effects, they ​ were dissected both vertically and longitudinally in the area dodders wrap on the hosts.The images under light microscope were captured under magnification ​ ​ (200X). ​ Result ➤Dodder wrapping around its host’s stem ➤horizontal section of dodders invading Plantago asiatica (200X) ​ ​ ➤vertical section of dodders invading the phloem of Plantago asiatica (200x) ​ ​ ​ 4.Results 4.1 Collected data Since we found no dodders growing in the fields, no relevant data was collected. 4.2 Experiments In the experiments, we mainly focused on two aspects. The first one is dodder’s preference on hosts and the second one is dodder’s growing behaviour. For experiments including the growing behaviour of dodders, two set of plants and their control plants are used in order to improve the accuracy of the data collected. Aspect 1: Dodder’s preference of hosts Hypothesis We assume that dodders will choose dicots rather than monocots, and plants with higher sugar content as the hosts. 4.2.1 Effect of Dodders on host selection of monocots and dicots Objectives of experiment 4.2.1 To study the effect of dodders on host selection of monocots and dicots. To find out which plant, monocot or dicot, will dodder choose in three set of plants. Design of experiment Three sets of different species of plants are used in order to eliminate the effect of other factors on dodder’s preference on choosing hosts based on type of plants. Assume the distances from the seeds of dodder to each plant are constant. The independent variable is different types of monocot and dicots while the dependent variable is the number of dodder that wrap around each plant. For each set of plants, a control pot is set up in order to ensure the plants are healthy in the pots with dodder, which makes the result more reliable. ➤Lucky bamboo& Hill Gynura ➤ Welsh onion& Dicot B ​ ​ ​ ➤Monocot C& Dicot C ​ Set-up 1. Monocot A(Dracaena sanderiana/Lucky bamboo) x3 ​ ​ 2. Dicot A(Gynura cusimbua/Hill Gynura) x3 ​ ​ ​ 3. Monocot B(Allium fistulosum/Welsh onion) x3 ​ ​ ​ 4. Dicot B(Catharanthus roseus /Rosy periwinkle ) x3 ​ ​ ​ ​ 5. Monocot C(Chlorophytum comosum/Spider ivy) x3 ​ ​ ​ 6. Dicot C(Plantago asiatica /Chinese plantain) x3 ​ ​ ​ 7. Pots x9 8. Dodder seeds x120 (20@each pot) 9. Soil x2packs Procedure 1. A Lucky bamboo and a Hill Gynura are planted in a pot with soil. 2. 20 dodder seeds are sowed on the soil midway between Lucky bamboo and Hill Gynura. 3. Observe and record the result regularly a week after germination of dodder seeds. 4. Repeat steps 1-3 with set B and set C of monocot and dicot. Result Monocot A( Dicot A( Lucky​ Hill​ bamboo)(number of Gynura)(number of ​ ​ dodders host on plant/20 dodders host on plant/20 seeds of dodders) seeds of dodders) Number of dodders on 3(15%) 2(10%) plant Monocot B( Dicot B(Rosy Welsh​ ​ onion)(number of periwinkle)(number of ​ ​ dodders host on plant/20 dodders host on plant/20 seeds of dodders) seeds of dodders) Number of dodders on 4(20%) 5(25%) plant Monocot C( Dicot C( Spider​ Chinese​ ivy)(number of dodders plantain)(number of ​ ​ host on plant/20 seeds dodders host on plant/20 of dodders) seeds of dodders) Number of dodders on 7(35%) 9(45%) plant Analysis According to the data summarized in tables above, dodder will host on every plant they encounter regardless of its type. Therefore type of plant may not be a determinant of dodder’s host selection. 4.2.2 Effect of Dodders on host selection of plants with higher or low sugar ​ ​ content Objectives of experiment 4.2.2 To study the effect of dodders on host selection of plants with higher and low sugar content.