# Use of _Chlorella vulgaris_ and _Ulva lactuca_ as Biostimulant on Lettuce
## 3 Results and Discussion  
### Algal Extract Dilutions Treatment on Seeds  
The measured EC values of the crude extracts from _U. lactuca_ and _C. vulgaris_ (Table 1) were below 2 dS/m (above that, it was considered that the extract was too conductive for plants, which can drive plants cells into osmotic stress and have a negative impact on the plants itself), only for the dilutions of 15% and 50% of _C. vulgaris_ and 25% of _U. lactuca_. pH (Table 1) was approximately between 5.7 and 5.9 for _C. vulgaris_ dilutions and in the range of 6.7 and 7.0 for _U. lactuca_ dilutions; since this parameter was not very different between the extract dilutions, it cannot be considered as a selection standard for the choice of the best treatment.  
The physical-chemical characterization of extracts is critical for successful outcomes. As a result, the electrical conductivity of the tested extracts was revealed to be not so suitable for lettuce growth, because previous research has found that using nutrient solutions with an electric conductivity greater than 1600 S/cm to cultivate lettuce may cause nutrient imbalance, resulting in decreased leaf number, area, and weight. Furthermore, high electrical conductivity values in the nutrient solution (>1700 S/cm) might cause early bolting as well as chlorotic and necrotic patches on lettuce's lower leaves. Another important aspect in plant growth is pH; thus, nutrient solutions with pH values around 6 are advised for lettuce development [7; 8; 9].  
These results had consequences on the germination rate (GR) performed by the lettuce seeds during the germination assay seven days after the start of the experiment in Petri dishes (Figure 1). After seven days, no changes were observed in the assay. The GR of lettuce seeds treated with 50% C. _vulgaris_ was more than 50% lower than the GR of 15%, that is much higher than 75% and 100%. For the beans treated with _C. vulgaris_, there were no statistical differences between the dilutions. Regarding the _U. lactuca_ treatments in beans, the difference is irrelevant with a lower value of 50%. In lettuce, the best results were obtained with 25% and 75% _U. lactuca_, however, these results were not statistically significant when compared with the control.  
\begin{table}
\begin{tabular}{c c c c} \hline \multicolumn{1}{c}{**Algal Extract Dilutions**} & **pH** & **EC (mS)** \\ \hline _Chlorella_ & 15\% & 5.69 & 0.54 \\  & 50\% & 5.91 & 1.67 \\  & 75\% & 5.88 & 2.19 \\  & 100\% & 5.90 & 2.33 \\ _Ulua_ & 25\% & 6.79 & 1.27 \\  & 50\% & 7.04 & 2.70 \\  & 75\% & 6.67 & 2.86 \\  & 100\% & 6.97 & 3.23 \\ \hline \end{tabular}
\end{table}
Table 1: pH and electrical conductivity (EC) of the algal extract dilutions.  
The results in lettuce demonstrated that the physico-chemical parameters in _C. vulgaris_ add a direct impact in the seed germination, where pH and EC were out of limits. Unlike the _C. vulgaris_, the _U. lutuca_ extracts demonstrated that the pH can interact with the negative impact of EC where, at 100%, there is lower germination without being significantly different.  
According to [PERSON] and [PERSON] and [PERSON] (2018), whose experiment was performed on lettuce and tomatoes with the acetone extract of _U. lactuca_, a low concentration of extract had a positive effect on the GR. The only exception is presented with the 75% _U. lactuca_ dilution that appeared to be a very efficient dilution for beans. The above-cited study, as an answer to this effect, explains that these results can be connected to the action of free phenolic compounds able to stimulate the germination of different plants.