Interview with Evelien van Tongerlo

Together with Heleen Bastiaanssen and Marcel van Twist

As a breeding company, research is an important pillar, the results of which are of great importance for innovation in the broadest sense of the word. Much of Anthura's research focuses on the plant itself. The constant desire to understand the different aspects of a plant lies at the root of this. The growth of a plant and the factors that influence it, determine the final cultivation time and quality. It is therefore very important that you understand and measure the growth properly. We talked to Heleen Bastiaanssen (Breeding Manager, Anthura/right), Marcel van Twist (Cultivation Research Manager, Anthura/(left) and Evelien van Tongerlo PhD/middle, about their joint research into plant growth.

Evelien van Tongerlo is from Brakel, Gelderland, and this daughter of a horticulturalist chose to become a biology teacher after finishing secondary school. After her training, it turned out that teaching adolescents was not for her and she changed course. She wanted to work with her hands and became a car mechanic at Citroën and Porsche. After a few years she could not envisage herself in this role for the rest of her professional life, so she started a Master's degree in plant sciences at Wageningen University & Research (WUR). The choice was partly based on her love of practical subjects. After her Master's degree, she was invited by the WUR, among others, to do PhD research. She started as an intern at Anthura and did her PhD research on growth in Phalaenopsis at WUR in conjunction with Anthura, Signify, B-Mex and STW/NWO. Last July, Evelien received her PhD on this research.

Evelien van Tongerlo

"In the end, blood is thicker than water. As the daughter of a horticulturalist, I used to help out when other children had the day off, but after many wanderings I have now become a plant researcher, partly working in the field. I find working with and researching plants incredibly fun and interesting."

Why was it decided to conduct a study on growth in Phalaenopsis? Heleen: Anthura wanted to get more control of growth rates under different circumstances, like light and temperature, and to be able to measure this growth rate. On the one hand, our breeding department wanted to get a good picture of the variation in growth within Phalaenopsis. Phalaenopsis can grow in different places and under different conditions. The origin of this plant can even be traced back to several continents, each with a different climate. On the other hand, the cultivation research department questioned how we could best measure the growth of a Phalaenopsis plant and thereby better predict its eventual growth. To measure growth under different conditions, you need a method and we didn't have one. We didn't know how to develop a measurement method because we didn't fully understand growth.

How did the cooperation in this study come about? Heleen: In many growth measurements, light is the limiting factor and Marcel's cultivation research at Anthura showed that this is not the case with Phalaenopsis. Our breeding and cultivation research departments, together with Professor Leo Marcelis and Anja Dieleman, have made a draft proposal for a PhD student from the Horticulture and Product Physiology research group at the WUR to investigate how the different manifestations of growth work. We looked for partners; other companies who were also interested in this research, and besides the WUR and NWO/STW these turned out to be Signify and B-Mex. Subsequently, a grant application was submitted to NWO (formerly STW). Our proposal 'Understanding Phenotypes of Orchids (UPO) was then honoured.

How did you get involved in this research? Evelien: After obtaining my Master's degree, I was approached by the WUR with the possibility of doing this research, so I did a four-month internship at Anthura to see if I would like it. When that turned out to be the case, I officially applied for this PhD project. Obviously, I was chosen to do the research.

"It soon became apparent that it was a good fit and I really enjoyed working literally surrounded by plants."

Can you explain why this research seemed interesting to you? Evelien: I am practically-minded and this research was also partly practical. There was a link between theory and practice. Marcel did a lot of research, partly with input from breeders, so that the research received attention from different expertise, and that makes it special. I also had a good connection with the people I worked with during my internship, such as Heleen and Marcel, but also the Phalaenopsis breeding and cultivation research team.

Can you briefly explain what the research is about? Marcel: The research involves the influence of light and/or temperature on the growth of Phalaenopsis plants. The temperature variable is obvious, and the light variable mainly concerns light colour and intensity. What we actually want is to determine the quality of a plant before it flowers. This means that after this research we can draw conclusions about plant quality under different circumstances based on a young plant. The entire research took more than five years: six months of preparation, an internship, and four years of research. Evelien: Photosynthesis is the basic process in plants, in which CO₂ is absorbed through the stomata and then captured in sugars for growth. Crassulacean Acid Metabolism (CAM) is an adjustment in the photosynthetic system, caused by exposure to drought and high temperatures. CAM plants are found everywhere, but there has not been much research into them yet. Phalaenopsis is a CAM plant, which is why it is so interesting to study it (source: summary PhD Evelien).

How did you proceed at the beginning? Evelien: After establishing the frameworks and preconditions, we wanted to test as many plants as possible, because quantity makes for qualitatively reliable measurements. Heleen: We first set up climate cells at Anthura and started a trial. From a breeding perspective, we wanted genetic variation to see how each plant responded. We had selected 19 Phalaenopsis varieties for the first experiment at the WUR. This was the maximum feasible number of varieties to measure under four different conditions. Due to the limited number of treatments (two temperature and two light levels), we could not draw any conclusions about the response of Phalaenopsis under other conditions. In order to find out why a plant does what it does, we chose far fewer varieties and more treatments, such as temperature, light level, light recipe and light period, in follow-up trials. Measurements of CO₂ proved to be a good way of seeing how a plant deals with light and based on the measurements, you can then quantify the effect on growth. These measurements were the basis of the building blocks of the growth model of the Phalaenopsis plant. The measurements showed the following: 1. A higher temperature leads to smaller plants with fewer roots; 2. More light leads to larger plants with more leaves; 3. The combination of a higher temperature with more light during the vegetative phase (when the plants are not yet flowering) will subsequently lead to more branches and more flowers. Then I made a schematic model, linking the processes that are important for the growth and development of CAM plants. The model consists of three parts: 1. Photosynthesis (absorbing CO₂); 2. The distribution of sugars in the plant; 3. The growth of the plant.

Why is measuring growth so difficult? Evelien: More light usually means more production; we didn't see that in Phalaenopsis, so we wanted to know what the difference was. However, you must first understand the framework of the plant before you can make the connections. Actually, you can compare it with cars. If you put the tyres of a Porsche on a Mini, it will not suddenly go faster, because that is precisely what the engine does. So it is important to know which part of the plant's framework has which function.

What is Anthura's role in this? Marcel: Before the start of the project, we did most of the preparation. When measuring the growth times, we also started the first experiment. This took place even before the project started. We also made the plant cart with lighting and took measurements. Heleen: During the set-up of the trial we, as members of the supervisory committee, took a look and decided, together with Evelien, to take a step back in the number of varieties in order to study the response to certain circumstances. Evelien: The framework turned out to be different from what we thought. The blocks and layout of the framework appeared to be correct, but one block sometimes turned out to be two, with each block having a different function. For example, if you gave the plant light, one block proved to have more influence, and if you played with the temperature, the other block.

Why are both Heleen and Marcel involved from Anthura? Marcel: The aim of the methodology is twofold: to gain insight into the optimal growth process with a method that is comprehensible for crop research (Marcel) and to be able to measure the variation in plant material for breeding (Heleen). So it is actually in terms of its application in production, crop research and breeding that we want to understand the plant’s growth and to be able to compare it.

Heleen: Marcel (plant physiology) and I (genetics) both have different expertise in this. Plant physiology is difficult and through the research we can now interpret the results better together and see how we can use them for Anthura.

How did you further shape the research? Evelien: I examined in detail the causes of the results of the measurements by combining all kinds of measurements, such as CO₂ uptake, amount of sugars in the leaf, and growth. The research showed that the CO₂ uptake figure can be used to predict the growth rate of a plant. We performed these measurements in different growth phases. By doing so, we learned that you can tell something about a plant sooner, without having to wait for the growing season. The way CO₂ is captured can change in 24 hours. It was not yet clear how this happens in Phalaenopsis, especially at the end of the day. The research shows that Phalaenopsis does this differently from most CAM plants. At first glance, the Phalaenopsis way seems to be less efficient for growth, but it could also be that the plant is better protected against light as a result. (source: summary PhD Evelien) Marcel: The research project became more and more important, essentially for understanding Phalaenopsis growth, and this deeper knowledge led us to its application. Based on fewer breeds, we started investigating more details to see which block was where: using two varieties to see what the differences were. There was already basic information from the study with 19 varieties. Each time, we chose two plants that you thought would react differently and sometimes we were surprised. When investigating the amount of light, there were often no differences in dry weight gains, which we had not expected.

"By doing so, we learned that you can tell something about a plant sooner, without having to wait for the growing season."

In a nutshell, what are the results of the research? The measurements of CO₂ uptake can be used to predict the quality of flowering plants and thus quickly select plants of good quality. CO₂ uptake can be indicative of vegetative growth despite differences in varieties. Vegetative growth is important for growth and quality, so better vegetative growth results in better generative growth and better flower quality. The CO₂ uptake of a plant in 24 hours is an indication of the quality of flowering.

Heleen: The research has taken a long time because one cycle takes 11 months: from setting up the plant to flowering, and then analysing the data. The long growth cycle is due to the fact that a Phalaenopsis plant is a shade plant with a mechanism that allows it to grow with the ‘brake’ on (CAM mechanism). And we don't know how to take the brake off. If we take the brake off in one place, it comes back somewhere else. Evelien: If we can figure out how to take the brakes off and make the cycle shorter, we can use the CAM mechanism in long-term food production. With that knowledge, the food chain can produce more in a more environmentally conscious way. Then an onion or potato can grow under better and faster conditions. Marcel: We're looking for that one growth measurement that can be predictive in ‘x’ months from now. The assumption is that it is CO₂. In the production of starting material, we can better predict when a variety is ready for delivery and this also applies to growers: first vegetative, then generative. The grower can then also predict when a variety will be ready, at the desired time and with the desired quality.

Are there any outcomes/results that are surprising? Heleen: We have compared Phalaenopsis with a Kalanchoe. Kalanchoe is considered to be a model CAM plant. You would therefore expect that measurements taken on Kalanchoe would also be translatable to Phalaenopsis. However, our research showed that Phalaenopsis is very different and gives different reactions. The growth model of a Kalanchoe does not apply to Phalaenopsis, which means that we have to research everything related to Phalaenopsis ourselves. We already knew that Phalaenopsis is not a tomato, but now we know that Phalaenopsis is not a Kalanchoe and that one Phalaenopsis is not like another. Evelien: Furthermore, for a scientific study, this research was pretty special. It was practical and there was good contact between the companies, with the university, actually between everyone involved. Also, nobody was afraid to ask each other critical questions, which made it special for everyone involved.

What will Anthura do with the results?

Marcel: With regard to cultivation research, we now have more insight into the genetic variations between different Phalaenopsis varieties in response to temperature and light. This means that we can select and have more insight into a possible brake during growth. CO₂ uptake is an important predictor of plant growth and quality and we can now make that selection at an earlier stage.

Heleen: In the breeding programme, we are now going to look at which measurements we can extend in order to be able to predict at an early stage when a plant will be fully grown under certain conditions and with what quality. What measurements do we need to record growth and development, and how should we measure CO₂ uptake? There's still plenty to do, so...

Evelien, what are your plans? Evelien: After my PhD, I took a course in cybersecurity. I enjoyed it so much that I now teach that course myself. IT has always attracted me and I really like data as well. It also gives me a good feeling that by teaching the course I can make a difference to people, because they can really benefit from it. Just like the research for Anthura actually.

For the summary of the PhD research, click here. For the complete PhD research, click here.