Sorghum plants treated with potassium nitrate (KNO3) and silicon (Si) showed better performance in water deficit conditions. The grain yield was 32% higher in the plants treated with potassium nitrate, in comparison with plants that had not received the chemical element. The silicon application had positive impacts in the mitigation of the effects of drought on leaf water potential and photosynthesis, as well as other plant benefits. The plants were assessed in the pre-flowering stage, when the sorghum is more affected by the lack of water. The studies, led by Embrapa and the Federal University of Lavras (UFLA), strengthen the knowledge base on sorghum's tolerance to drought and on the impacts of climate change on agriculture. Sorghum plants treated with potassium nitrate (KNO3) and silicon (Si) showed better performance when faced with water scarcity. This was a research finding from a study that was developed at Embrapa Maize and Sorghum, in partnership with the Federal University of Lavras (UFLA). The study aimed at assessing the crop's response, anticipating some effects of climate change, like reduced rainfall. The scientists assessed plants cultivated under water deficit pre-flowering, the period of sorghum's development when it is more affected by water deficiency. “Hence the stress was imposed in that period, which is also called rubberizing stage, if one may the expresion used by sorghum growers”, reports the Embrapa researcher Paulo César Magalhães. The researchers showed that, in drought conditions, the plants treated with potassium nitrate showed higher levels of chlorophyll, higher photosynthesis rate, better transpiration, other improved indicators and higher contents of Magnesium (Mg), Sulphur (S), Copper (Cu) and Iron (Fe), as opposed to those that were not treated with potassium nitrate. The plants that received the nitrate also had greater growth and a yield 32.2% higher than those that were not treated with KNO3. "Through such variables, it is possible to assert that KNO3 induced drought tolerance in sorghum plants submitted to severe water stress at the pre-flowering stage", Magalhães observes. As for the silicon application, the scientists observed a mitigation of the effects of drought on the leaf water potential, photosynthesis, and root system morphometrics (morphologic measurement and characterization of the root system). Moreover, the element worked positively on the plant's antioxidant system and sugar content. “These positive effects contributed to higher grain yield and thus to higher drought tolerance”, Magalhães details. He explains that tolerance to droughts is related to a mechanism mediated by a protein chain called aquaporins, which cross the cell membrane. They selectively drive water molecules in and out of the cell. The study identified TIP 4 aquaporin as most responsive to drought in sorghum plants. These results can help other studies further improve sorghum's performance in water stress conditions. Awarded thesis The findings from this study were presented in Roniel Geraldo Ávila's PhD thesis entitled “Induction of drought tolerance in sorghum cultivated under water deficit and suplemented with silicon and potassium nitrate in pre-flowering”, advised by the researcher Paulo César Magalhães, from Embrapa Maize and Sorghum, and professor Amauri Alves de Alvarenga, from UFLA. The work has already generated four papers, one of which published on the journal Silicon (on the right). The thesis was awarded the first place at the university in the area of Plant Physiology during their 2019 Graduate Congress. The award works as a pre-selection for the Capes award. Participants Besides Paulo César Magalhães and Roniel Ávila, the other research participant are: Amauri Alves de Alvarenga and Éder Marcos da Silva, from UFLA's Biology Department; Carlos César Gomes Júnior, do Instituto de Ciências Naturais da Universidade Federal de Alfenas (Unifal); Ubiraci Gomes de Paula Lana, da Embrapa Milho e Sorgo; e Thiago Corrêa de Souza, da Unifal. The data from the study with silicon was published on the scientific journal Silicon with the title “Silicon supplementation improves tolerance to water deficiency in sorghum plants by increasing root system growth and improving photosynthesis”. Recognized drought tolerance The studies also reinforced the knowledge about sorghum's tolerance to droughts. “This trait has been proven in several studies by Embrapa and by other researchers in Brazil and abroad. However, the plant still suffers with water deficit. That is why we set out to study the effects of both potassium nitrate and silicon supplementation”, Magalhães reports. The scientist reaffirms the concern with climate change, since they already are a reality, he states, and will cause abrupt alterations to the climate in a very short span of time. “Such changes include lack of water and lack of rainfall, which will certainly be impacting factors for agriculture. Therefore we study everything that is possible to minimize or mitigate the effects of water deficit on the plants”, he underscores. Controlled experiment “As we decided to assess several very refined traits, we have chosen not to perform this experiment in the field”, he reports. The research was conducted in a greenhouse, in controlled conditions with the help of devices to make the necessary measurements. “For example, gas exchange measurements would be more complicated to perform in the field. But the greenhouse is a more controlled environment and practical to measure”, Magalhães details. In those conditions, it was possible to prove that both potassium nitrate and the silicon rates in the pre-flowering period benefited the plants by mitigating the effects of water deficit. The researcher Paulo Cesar Magalhães talks about the use of potassium nitrate and silicon to mitigate the effects of drought on the plants.. Translation: Mariana Medeiros