## 3 Results and Discussion
### Optical Microscopy Observations  
The presence and abundance of conidia and chlamdsopores and the morphology of hyphae were analyzed in order to determine the effects of the blue-light laser as a function of irradiation time. Both non-irradiated and irradiated samples presented the following morphological features: long, either straight or sinuous, segmented (septate), and predominantly cylindrical-shaped hyphae; small, green-colored, and ovoid-shaped (globular) conidia (microconidia); chlamdospores (asexual spores with a thicker cell wall and a higher survival rate than microconidia), which were globular in shape, intercalary, or terminal (Figure 5). The irradiation did not affect the shape of the hyphae, conidia, and chlamdospores of _T. atroviride_, as can be seen in Figure 5.  
The abundance of chlamdospores was marginally increased after the 3 \(\times\) 300 s irradiation time compared to the control, but it was not statistically significant, as quantified from microscopic images (Figure 6). The quantification of chlamdospores is not easy as they are bound to mycelium and are difficult to separate. The trend indicates a possible effect of irradiation on the formation of chlamdospores, but more investigations are necessary in this respect. Irradiation for 3 \(\times\) 60 s slightly increased the production of conidia, and longer irradiation (3 \(\times\) 300 s) induced a statistically significant increase in conidiation of _T. atroviride_ (Figure 7). This is in agreement with the previous studies and shows that the general effect of light on conidial is in general independent of the species/strains, irradiation system, or other parameters. Interestingly, the diameter of conidia increased upon irradiation, an aspect that has not been investigated before. Figure 4: (**a**) UV–Vis spectra of _Trichoderma_ cultures grown on rice husks, non-irradiated (0 s) and irradiated for 3 \(\times\) 60 s and 3 \(\times\) 300 s with 0.271 \(\upmu\)moles/s 400 nm laser irradiation, after 15 days of incubation; (**b**) the absorbance values at 260 nm and the ratios 260 nm/230 nm and 260 nm/280 nm of _Trichoderma_ cultures grown on rice husks, non-irradiated (0 s) and irradiated for 3 \(\times\) 60 s and 3 \(\times\) 300 s with 0.271 \(\upmu\)moles/s 400 nm laser irradiation, after 15 days of incubation. Figure 5: _Cont._  
An interesting observation was that the conidia had the tendency to cluster around the liquid-air interface when the longer irradiation of 3 \(\times\) 300 s was applied (Figure 8), a phenomenon that was not observed in the non-irradiated sample or for the shorter irradiation times. This migration to the liquid-air interface indicates that the conidia could be more hydrophobic upon irradiation compared to the control, but this needs to be confirmed. In a previous study, hydrophobin HFB2, known to be involved in sporulation [42], was identified in the culture of _T. reesei_ grown in light and on cellulose [25]. HFB2 was shown to be highly expressed in _T. reesei_ grown in the presence of complex plant polysaccharides and as response to N and C starvation [43]. Hydrophobins have been shown to be required for conidial hydrophobicity in _C. rosea_[44]. Correlating these data and considering our substrate, rice husks, with their complex lignocellulosic structure that is hard to decompose,  
Figure 5: Morphological structures present in _Trichoderma atroviride_ strain irradiated at 0.271 \(\upmu\)moles/s: (a–c) (40\(\times\) objective); (a\({}_{\mathbf{1}}\)–c\({}_{\mathbf{1}}\)) (100\(\times\) objective, with immersion). Arrow indicates chlamdospores. White labelled bars represent dimension at microscopic level—50 \(\upmu\)m.  
Figure 6: Relative abundance of chlamdospores in the irradiated and non-irradiated _T. atroviride_ The columns with the same letter do not differ significantly. Bars are \(\pm\)error bars, \(\alpha\) = 0.05, \(n\) = 6.  
we speculate that the laser irradiation stimulated the production of hydrophobins that probably increased the hydrophobicity of the conidia.