**5. Discussion**

The experiments showed that the effect of different variables is often connected to similar affects in terms of mushroom morphology. For example, high humidity and substrate amount will affect mushroom size. And single variables are related to more than one affect. For example, humidity also affects curvature. Despite this, there is a fairly predictable relationship between each of the environmental parameters described in the experiments. Cap curvature is related to humidity, cap size is related to CO2, stalk bend is related to gravity, and overall mushroom size is related to substrate amount, as seen in Figure 11. *Biomimetics* **2022**, *7*, x FOR PEER REVIEW 15 of 18

**Figure 11.** The overlay of the triplicate 3D scans of the mushrooms (at the same scale) grown under the same environmental conditions: The average sizes and the overlayed mushrooms in the (**a**) humidity (**b**) CO2; (**c**) gravity; (**d**) substrate amount experiment. **Figure 11.** The overlay of the triplicate 3D scans of the mushrooms (at the same scale) grown under the same environmental conditions: The average sizes and the overlayed mushrooms in the (**a**) humidity (**b**) CO<sup>2</sup> ; (**c**) gravity; (**d**) substrate amount experiment.

The experiments also demonstrate that fungi exhibit linear parametric properties when a single parameter is changed, at least for the limited parameters and a single family of mushrooms tested here. As shown in Figure 12, each parameter change exhibits a distinct trend, although the high degree of variability exhibited in relation to mushroom size

achieve a higher significance of results. In all experiments, further replicates would need to be conducted to provide more significant relationships. Nevertheless, using these parameters, it should be possible to predict the morphology of mushrooms given specific

Future research should also explore (1) the critical thresholds where growth is inhibited; (2) tipping points which lead the developmental pathway for the mushrooms to change; or (3) where normal development is critically disrupted where changing the variable no longer affects (or affects as expected) the mushroom morphology. For instance, mushroom growth may not be expected at very low humidity, or mushrooms cannot

parameters—within the range of values tested by the experiments.

grow above a certain size even if the amount of nutrients are increased.

The experiments also demonstrate that fungi exhibit linear parametric properties when a single parameter is changed, at least for the limited parameters and a single family of mushrooms tested here. As shown in Figure 12, each parameter change exhibits a distinct trend, although the high degree of variability exhibited in relation to mushroom size and substrate amount should be noted. More replicates are required in the future to achieve a higher significance of results. In all experiments, further replicates would need to be conducted to provide more significant relationships. Nevertheless, using these parameters, it should be possible to predict the morphology of mushrooms given specific parameters—within the range of values tested by the experiments. *Biomimetics* **2022**, *7*, x FOR PEER REVIEW 16 of 18

**Figure 12.** The mushroom growth—variables relationship. **Figure 12.** The mushroom growth—variables relationship.

**6. Conclusions**  This paper asked the question: Is the growth of the mushroom fruiting bodies parametric? Or, more precisely: can mushroom morphology be predicted by altering the environmental parameters? As a designer, can we design fungal morphology using a parametric design approach? While we tend to think of biological systems as highly complex and non-linear systems, these albeit limited set of experiments have shown that given de-Future research should also explore (1) the critical thresholds where growth is inhibited; (2) tipping points which lead the developmental pathway for the mushrooms to change; or (3) where normal development is critically disrupted where changing the variable no longer affects (or affects as expected) the mushroom morphology. For instance, mushroom growth may not be expected at very low humidity, or mushrooms cannot grow above a certain size even if the amount of nutrients are increased.

### fined environmental conditions including factors such as CO2, humidity, orientation etc. **6. Conclusions**

we can see, within the limits of these experiments, linear relationships between environmental parameters and morphology outcomes. This points to the possibility of computational simulations for these systems and for the development of parametric-like software to estimate aspects of biological growth. It is also worth noting, however, that given the small sample size of the experiments (restricted to a single family of edible mushrooms) and the often significant, variation between mushrooms, we also need to recognize that these environmental factors are linked, and that mushroom morphology is highly sensitive to slight variations in conditions. This means that any attempt to model and predict the outcomes of different growth conditions will need to be, to some extent, probabilistic. The next step in this research will be to build such a model. While the ability to alter the morphology of mushroom growth may be useful in, for example, agricultural contexts, these experiments are practical thought experiments. By trying to take a parametric design concept (which is well discussed in generative and computational design in architecture) and applying it to biological systems, we are revealing both its strength and weakness as a concept. With rapidly growing (literally and metaphorically) interest in the use of biomaterials in design and ideas of harnessing biological fabrication emerging from fields such as engineering living materials, this paper offered This paper asked the question: Is the growth of the mushroom fruiting bodies parametric? Or, more precisely: can mushroom morphology be predicted by altering the environmental parameters? As a designer, can we design fungal morphology using a parametric design approach? While we tend to think of biological systems as highly complex and non-linear systems, these albeit limited set of experiments have shown that given defined environmental conditions including factors such as CO2, humidity, orientation etc. we can see, within the limits of these experiments, linear relationships between environmental parameters and morphology outcomes. This points to the possibility of computational simulations for these systems and for the development of parametric-like software to estimate aspects of biological growth. It is also worth noting, however, that given the small sample size of the experiments (restricted to a single family of edible mushrooms) and the often significant, variation between mushrooms, we also need to recognize that these environmental factors are linked, and that mushroom morphology is highly sensitive to slight variations in conditions. This means that any attempt to model and predict the outcomes of different growth conditions will need to be, to some extent, probabilistic. The next step in this research will be to build such a model.

an alternative approach to the often gene-centric idea of engineering living organisms. We have shown that the developmental plasticity of mushrooms allows us access to control

Future work will need to extend the parameters explored and examine more closely their interrelationships as well as to increase the types of biological systems and processes amenable to change. It will also need to address the challenges of uncertainty of outcomes

which are inherent in the design with biological systems.

may also be true of other sorts of biological systems.

While the ability to alter the morphology of mushroom growth may be useful in, for example, agricultural contexts, these experiments are practical thought experiments. By trying to take a parametric design concept (which is well discussed in generative and computational design in architecture) and applying it to biological systems, we are revealing both its strength and weakness as a concept. With rapidly growing (literally and metaphorically) interest in the use of biomaterials in design and ideas of harnessing biological fabrication emerging from fields such as engineering living materials, this paper offered an alternative approach to the often gene-centric idea of engineering living organisms. We have shown that the developmental plasticity of mushrooms allows us access to control parameters outside the living cell of the mushroom that in turn remotely influence, rather than control, the material outcomes of mushroom growth. What is true for mushrooms may also be true of other sorts of biological systems.

Future work will need to extend the parameters explored and examine more closely their interrelationships as well as to increase the types of biological systems and processes amenable to change. It will also need to address the challenges of uncertainty of outcomes which are inherent in the design with biological systems.

**Author Contributions:** Conceptualization, D.O.; methodology, D.O., M.D.-R., R.M. and M.Z; validation, D.O., M.D.-R., R.M. and M.Z; formal analysis, D.O.; investigation, D.O.; resources, D.O.; data curation, D.O.; writing—original draft preparation, D.O.; writing—review and editing, M.D.-R., R.M. and M.Z.; visualization, D.O.; supervision, M.D.-R., R.M. and M.Z.; project administration, D.O., M.D.-R., R.M. and M.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Hub for Biotechnology in the Built Environment funded by Expanding Excellence in England (E3), Research England.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**


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