Effect of drought in levels of Na, Al, P and S in maize and common bean leaves Lázaro Hernández1, Daviel Gómez1, Annekathrin Rumlow2, Ariel Turcios2, Inaudis Cejas1, Leyanes Díaz-López1, Lourdes Yabor1, Oscar Vicente3, Jutta Papenbrock2, José Carlos Lorenzo1 1 Laboratory for Plant Breeding, Centro de Bioplantas, Universidad de Ciego de Ávila, Ciego de Ávila 69450, Cuba. E-mail: jclorenzo@bioplantas.cu. URL: www.bioplantas.cu. 2 Leibniz University Hannover, Institute of Botany, Herrenhaeuser Str. 2, D-30419 Hannover, Germany; Jutta.Papenbrock@botanik.uni-hannover.de 3 Universitat Politècnica de València, Institute of Plant Molecular and Cellular Biology (IBMCP, UPV-CSIC), Camino de Vera s/n, 46022 Valencia, Spain; ovicente@ibmcp.upv.es Results Introduction Maize is the second most important agricultural crop globally and common bean is one of the world’s important grain legumes, consumed as a dietary staple worldwide. In the past decades, extreme weather conditions, such as drought, caused by climate change have disrupted global food production. Drought stress is generally linked with several biochemical and physiological changes but its effects on mineral contents have not been studied deeply. This work focuses on the identification of previously unreported potential chemical markers for drought stress, which could be used for the rapid identification of putative stress tolerant maize and common bean plants in crop breeding programs. Substantial contributions of worldwide research groups are still required to understand the mechanisms underlying the relationship between drought and mineral nutrition at early stages of plantlet growth. Plantlets at 96 h of lack of irrigation. Plantlets at 48 h of lack of irrigation A Maize Plantlets at 0 h of lack of irrigation. Plantlets at 96 h of lack of irrigation. B Common bean Plantlets at 0 h of A Interaction of the two experimental factors: plant specie and time of lack of irrigation. Original data were transformed for the statistical analysis according to y´=2*arcsin(y/100)0.5. Results with the same letter are not statistically different (Two-Way ANOVA, Tukey, p>0.05). OCV=87.44%. Materials and Methods B Independent factor: plant specie. Results with the same letter are not statistically different. OCV=39.77%. After harvesting in Germany, a selection procedure to rule out unqualified seeds of maize (cv. Tuzón) and common bean (cv. Milagro Villaclareño) was performed. Seeds with 12% moisture content (fresh weight basis (ISTA, 2005)) were stored at 4oC in the dark in hermetically closed glass containers. Duration of water shortage to cause death of 50% of stressed plantlets ( Hernandez et al., 2015). C Independent factor: time of lack of irrigation. Results with the same letter are not statistically different. OCV=82.15%. Mineral analysis of plantlet leaves under drought stress: Figure 1: Effect of lack of irrigation on maize and common bean plantlets. Pots were irrigated every day with 25 ml water during 10 days, then watering was suspended. OCV means Overall Coefficient of Variation = (Standard deviation/Average)* 100. To calculate this coefficient, average values of each treatment were considered. The higher difference between the treatments compared, the higher the OCV. Figure 2: Effect of lack of irrigation on maize and common bean plantlets. Pots were irrigated every day with 25 ml water during 10 d, then watering was suspended. 480°C / 8h Cooling the samples (21-23 oC) 1.5 ml 66% nitric acid was added 10 min 13.5 ml of ultra-pure water was added. Solutions were filtered and stored in vials at 4 oC Contents of Al, B, Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn were determined. Table 1: Mineral composition of maize and common bean leaves under drought stress. Elements Control (µg g-1 dry mass) Drought for 51.8 h (µg g-1 dry mass) Statistical significance (t-test. p=0.05) Drought effect OCV (%)* Classification of OCV** Maize   Na 3530.35 1360.10 Yes Decrease 62.8 High Al 56.40 102.15 Increase 40.8 Medium P 7452.68 5036.40 27.4 Zn 25.25 19.34 18.7 Low K 57668.35 47838.70 13.2 Mn 51.23 57.51 8.2 Sr 8.77 7.91 7.3 B 59.54 54.19 No None 6.7 Ba 3.00 2.77 5.6 Mg 694.93 738.28 4.3 S 1892.44 1807.28 3.3 Fe 66.59 67.09 0.5 Ca 6094.16 6060.73 0.4 Total content of elements 77603.69 63152.45 Common bean 18.47 45.36 59.6 4356.35 7107.84 33.9 2862.23 2419.34 11.8 6245.74 7304.91 11.1 30548.55 34851.19 9.3 80.37 90.43 8.3 122.81 110.15 7.7 26.93 29.32 6.0 11.54 12.34 4.7 1232.70 1154.10 54.32 57.96 4.6 37.13 36.66 0.9 26499.57 26182.85 72096.71 79402.45 * Overall coefficient of variation = (Standard deviation/Average)* 100. To calculate this coefficient, average values were considered. The higher difference between the two conditions compared, the higher the overall coefficient of variation. ** The OCVs were classified in three categories: Low from 0.4 to 21.2%, Medium from 21.2 to 42.0% and High from 42.0 to 62.8%. Acknowledgments This research was supported by the Institute of Botany (Leibniz University of Hannover, Germany) and the Bioplant Centre (University of Ciego de Avila, Cuba). This research was also partially supported by the German Academic Exchange Service (DAAD) through a grant to Dr. José Carlos Lorenzo Feijoo.