This was written in 2017 when I first started my Master program in Taiwan. I wrote it as a personal blog piece and a reflection of some of the ecology lectures I attended. It’s an interesting piece, but it’s mostly here for completeness.
November 10, 2017
One of the assignments I have is to write a reflection on some of the lecturers who presented in the past few classes. Since I’m suddenly free from lecture today, I figured, it would be a good chance to catch up on some of the reflection pieces.
Lecture on Seed Dormancy and Germination*
This lecture was presented by Ching-Te Chien, a researcher and professor at National Taiwan University. The basic premise of his study was to conduct a comprehensive study on seed dormancy and examine the different environmental or epigenetic factors that may impact the rate of germination or the length of dormancy in several plant species native to the Taiwan region. Seed dormancy is dependent on a number of factors such as premature embryo development, water and gas permeability of the seed coat, mechanical resistances of the seed (ie pits), and metabolic blocks in the embryo. Essentially, factors that prevent nutrients or energy from getting to the embryo. These factors can be broadly categorized into four classification schemes: Morphological, Physiological, Morphophysiological, and Physical Dormancy. Many times, there is a combination of factors that lead to persistence of the overall dormancy in the seed, such cases are thus categorized as Combination Dormancy. This classification scheme was modified based on M. G. Nikolaeva’s original 1967 seed dormancy classification system. This system is actually quite practical and still predominately used today. Chien categorically examined several species for seed dormancy class and requirements to determine if there were any major trends in Taiwanese plants.
Chien tested a number of species and their dormancy rates in Taiwan. He compared the species by measuring the rate of germination (number of seeds germinated over time) after specific treatments to the the seeds. Examples of conditions include differential temperature treatments, scarification of seeds, acidification, heat treatment, and several other methods to simulate seed processing in nature. Chien was able to observe differences between different seed types for each plant and determine relative conditions for germination. He examined the developmental differences as well as by tracking changes in the embryo development throughout the germination process. This allowed him to evaluate the any pre-development stages of the embryo and determine how significant different stages were on the overall germination rates. The reason he did this was largely to observe seeds with prolong dormancy phases. He showed that some seeds had extensive development within seeds and can contribute to the overall dormancy time period. Seeds with underdeveloped embryos often required additional incubation times before germination, especially compared to embryos that were more fully developed.
The amount of data collect for each temperature gradient, in particular, demonstrated the importance temperature had on the germination rates. This is critically important for future studies related to global climate change and can be important for understanding how plants can adapt to rapidly changing conditions. It was seen in most seeds, that a low temperature period was needed to stratify the seeds before germination. Chien showed this by germinating seeds under different temperature gradients and observing the total rate at each interval. The results largely demonstrated that seeds often grew better when subjected to periods of lower temperature (ie winter climate) before germination.
Chien’s study was quite interesting in that during his project, he noticed differences between seed dormancy between regions and habitats despite being the same species. Part of the scope of his talk was focused on what might be considered a potential maternal environmental effect, or seed memory; that is the ability for the progeny of the plant to “remember” optimal conditions from previous generations. This might be considered a part of an epigenetic factor that is changed from generation to generation. This is especially important when looking at the overall changes in the environment such as the increase in global warming and shifting weather patterns. However, it could also be looked at in a more evolutionary perspective. Perhaps because these species have been isolate in two different environments, they have begun to accumulate genetic differences and begun a slow speciation event in which the plant seed conditions have been selected for their particular environmental adaptations. These are questions that are not yet addressed in Chien’s talk, and could lead to a very interesting future study in which genetic divergence between seed traits could be use to determine fitness in particular environments, or rapidly changing environmental conditions.
Understanding how seeds germinate may seem like a very low impact study, but in reality, I feel that it’s quite important to understand the conditions in which seeds germinate. Because of dramatic global change, the slight shift in temperature by a few degrees could signify a large change in the number of seeds that germinate each year. With Chien’s talk, we see how important environmental factors such a temperature, moisture, and relative stability in an environment is. There are numerous factors that are critical for seeds to reach optimal conditions, and as we learn more about these conditions, we can make changes or identify specific solutions to prevent loss of species or habitat.
*note the seminar lecture was conducted in chinese, so… some of it was based on my interpretation of the presentation material and prior knowledge. Any error is solely my fault, and I do apologize ahead of time. Furthermore, I’m not a particular expert on this topic, and I simply want to write my thoughts on the research and maybe make personal notes so I can refer back to it if I need it in the future.
