Greenhouse — a tool… by ULRICH SCHURR
Greenhouse — a tool, its limitation and its perspective
For us researchers, a greenhouse is primarily a tool. A tool to provide us with plants and to undertake experiments in an intendedly limited set of environmental conditions. While we want to know the performance of plants on the field, we need to reduce the variability of the environment. The latter has such a huge complexity and — even more important — is so hard to predict that it is impossible to conclude directly on cause and effect. Here the greenhouse is a tool to reduce the complexity of nature. Research uses greenhouses in such a reductionistic approach, knowing that the “system plant” is determined by the genotype, the environment (being the set of environmental parameters) and the management of the plant (handling of plants).
The so-called phenotype (the structural and functional unity of a specific plant) develops from the toolbox of genes given to the individuum from the crossing of the parent plants, which is modified by the continuous processes of natural mutations. Therefore the genotype is the “memory” of generations and generations reaching far back in evolution. Genes that are expressed and allow improved performance under the respective environmental conditions will give the plant a better performance that might (but does not need to) improve the likelihood that these genes make it into into future expressed plant genomes. The variability of the genome -in the “memory approach” being the loss and even (intended) change in memory entries — is the prerequisite of adaptation. A static memory will not be able to evolve and thus allow the plant to adapt to future (not previously existing) conditions. However, the diversity of plants is due to the diversity of static to plastic genomes — at the time scale of beyond generation (?).
Beyond the genome, the phenotype of the plant develops over time — from germination to the time when we observe it — in interaction with environment and management. One can compare a plant with a craftsman, who has a toolbox (the genome), which has been filled by all its ancestors and modified by stochastic variability. This does not necessary mean that the craftsman/plant can use the tool — if they never experienced the challenge/stress before they might have formed a structure and function that is not able to withstand. E.g. a plant that has never seen drought before, will have developed a ratio between root (the structure of water uptake) and shoot (the structure that loses water) that is enough at high water availability to maintain the supply to the leaves, while it cannot cope at low water availability and high water demand from transpiration. In contrast, an adaptive plant, which is exposed to (even mild) stress before a drought occurs, might not spent as much biomass into the demanding leaves, but invest more into roots. In that context the structural — and in analogue ways the functional setup of the plant — is also a memory of the previous environmental conditions experienced by the plant over time. Explicitly, roots grow strongly in regions of the soil that offer high nutrient and high water availability — irrespective of the genetic setup. Therefore, the phenotype of a plant always contains history of various temporal scales — from evolutionary timescales through the more or less conservative genotype and from the lifetime of the plant itself, by its structure and habitus and it´s response to spatial and temporal variation of resources (water, nutrients, ..). This sets boundaries to the space of options that a plant has — from a nested set of “history constrains”, which are by far not independent from each other. Thus, even without a conscious mind, the plant “experiences” opportunities and challenges determined in evolutionary timeframe by its ancestors and from within its life. Thus, a plant´s memory though even very different in nature than the human memory, integrates many pasts and determines performance in the present.
Domestication, the process by which mankind turns wild plants into crops and makes them perform (usually better) under the conditions that humans expose the plant to — e.g. in greenhouses or agriculture — thus often reduces the fitness of plants in the complex and dynamic nature. Processes that are “costly” for the plants, but not needed any longer, because humans provide nutrients or protect plants from pests, can cause a reduction in intrinsic resistance against biotic or abiotic stress; while at the same time improving e.g. yield or quality for human use/consumption. Today´s elite plants are not escaping into the wild, as they often might not be able to compete well there. There are, however, also examples, where the introduction of plants (in many cases wild plants) to environments where they were not present before, causes a rapid expansion of the plant in its niche, because they can outcompete previously present plant species. An analogous process is the migration of plants into new regions due to change of climate or reduction of distance barriers [e.g. by globalization of transport of crops or crop parts (fruits, seeds, etc.)]. This is not a modern phenomenon but has been observed in previous centuries with new shipping routes following technological advancements. Therefore, the setup of the plant, as composed from its various “memory components” is also closely linked to plant distribution as well as with the usability of plants in human use.
Here the cycle closes, when humans use greenhouses to grow/produce plants in the reduced environmental complexity and in conditions safeguarded by humans. Here, we could talk of a co-evolution of human knowledge, engineering and design to optimize plant production (in management) with the plant, which — during domestication — adapts itself to perform best under the artificial conditions of a greenhouse (or agricultural management), which — in this sense — is a non-visual boundary of a dimension generated by humans to host and produce plants.
Prof. Ulrich Schurr is Director at the Institute for Bio- and Geo Sciences — IBG-2: Plant Sciences at Forschungszentrum Jülich. He is coordinating several large national and international projects — like the Bioeconomy Science Center (BioSC), the European (EPPN) and the German (DPPN) and the International (IPPN) Plant Phenotyping Network. Prof. Schurr was chairman of the European Technology Platform Plants for the Future and served as board member and Vice-President of EPSO (European Plant Science Organization).
Professionally, Dr. Schurr focuses on the dynamics of growth and transport in plants and their influence by varying environmental conditions. Insights into this are the basis of novel applications of plants in the vision of a sustainable bio-economy. To understand and translate these processes into practical applications, it is essential to capture quantitative information on key processes of plant systems in their interaction with dynamic environmental factors and to elucidate the underlying physiological and molecular mechanisms. Especially suitable for this purpose are novel methods and innovative experimental approaches, which are also a focus in his own work.
