Introduction

The offer of Brazilian hybrids of popcorn (*Zea mays* L. *everta*) with high yield and adaptation to edaphic and climatic conditions is small, which leads to importation of a large number of popcorn seeds (^{Catão and Caixeta, 2017}). However, popcorn production is growing and is an advantageous source of income due to added value of the product (^{Rocha et al., 2018}; ^{Kavan et al., 2019}). This growth is due, in part, to the selection, development, and adaptation of imported cultivars for the climate conditions of Brazil (Catão and Caixeta, 2017).

The use of seeds with high physiological potential is a preponderant factor for establishment of a successful crop (^{Catão et al., 2013}). Thus, seed technology has sought to refine the tests used to evaluate physiological potential, aiming for the results to express the performance potential of the lot to minimize the risk of using low quality seeds (^{Bittencourt et al., 2012}).

The characteristics of a seed lot can be evaluated by diverse tests that follow strict standards. Seed quality is routinely evaluated by the standard germination test, conducted under optimal environment conditions (Brasil, 2009). However, the result of that test overestimates the true values of plant emergence in the field, and results obtained from vigor tests are also necessary (^{Bertolin et al., 2011}). The ideal procedure is for vigor tests to be used together with the germination test to assist in decision making and increase the speed and efficiency of quality control (^{Bittencourt et al., 2012}).

Studies in seed technology have reported that rapid vigor test that produce consistent information are those related to physiological deterioration processes, such as those related to enzymatic and respiratory activities and cell membrane integrity. The electrical conductivity and potassium leaching tests fit in this category (^{Steiner et al., 2011}; ^{Souza et al., 2014}).

The potassium leaching test is based on the same principle as the electrical conductivity test, through evaluation of cell membrane integrity, only the parameter analyzed is changed. In this test, only the potassium ion (K^{+}) is quantified in the soaking solution. Lower vigor seeds have lower speed of structuring of membranes when soaked in water, and a consequence is greater release of exudates from the cell and, consequently, greater release of potassium (^{Marcos-Filho, 2015}).

The potassium leaching test requires from one to two hours to obtain results, thus allowing seed vigor to be evaluated in a fast and efficient manner (Marcos-Filho, 2015). This is fundamental for speeding decision making, especially in relation to the operations of harvest, processing, and sale (^{Marcos-Filho, 2015}).

Thus, the potassium leaching test has become prominent for evaluation of seed physiological potential, resulting in satisfactory data for various species, as for example triticale (^{Steiner et al., 2011}), rice (^{Barbieri et al., 2011}), and wheat (^{Douradinho et al., 2015}). However, data regarding use of the potassium leaching test in evaluation of popcorn seed vigor are only in the initial stage. Given this lack of information, the aim of this study was to determine the potential of the potassium leaching test in evaluation of the physiological quality of popcorn seeds.

Material and Methods

The study was conducted in the Seed Laboratory of the Plant Science Department of the Fundação Gammon de Ensino in Paraguaçu Paulista, São Paulo, using five seed lots from two popcorn cultivars (AP8203 and AP4512). Moisture content was determined and physiological quality was evaluated for samples from each lot and cultivar using the germination, first count of germination, and seedling emergence tests and specific procedures for carrying out the potassium leaching test.

Moisture content was determined by the oven method at 105 ± 3 ºC for 24 hours using two subsamples of approximately 10 g for each lot (^{Brasil, 2009}).

In the germination test, four replications of fifty seeds were used for each lot. The seeds were uniformly distributed on two sheets of germitest paper, moistened with distilled water in the amount of 2.5 times the weight of the dry paper, and placed in a Mangelsdorf germinator at 25 ºC with a 12-h photoperiod. The germination counts were made at four and seven days after sowing for determination of the percentage of normal seedlings (^{Brasil, 2009}). The results were expressed in percentage of germination in the first count and in the final count.

For the emergence test, four subsamples of fifty seeds from each lot were sown in the field, distributed at a depth of 3.0 cm and a spacing of 0.5 cm in furrows of 1.0 m length. The soil was moistened to approximately 60% of water retention capacity. On the tenth day after stabilization of stand, the number of emerged seedlings was counted and the results were expressed in percentage.

The effects of the soaking period (0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 4 h and 5 h), of the volume of deionized water (50 and 75 mL), of the number of seeds (50 and 100), and of the soaking temperature (25 ºC and 30 ºC) were studied in the potassium leaching test. The test was conducted using four subsamples of 50 or 100 seeds that were first weighed (precision of 0.0001 g), placed in plastic cups containing deionized water, and kept in a germinator for each period and at the temperatures predetermined for soaking. Readings were made directly through atomic absorption using a flame spectrophotometer. For calculation of potassium leaching, the reading obtained in the flame spectrophotometer, the volume of deionized water used (mL), and the weight of the samples (g) were considered. The result was expressed in μg of K/g of seed, i.e., ppm of potassium.

Analyses of variance were performed separately for each cultivar and test conducted using a completely randomized design with four replications. In the event of significant effects, the mean values were compared by the Tukey test at 5% probability, using the Sisvar 5.0 software (^{Ferreira, 2011}). Pearson linear correlation analysis was also performed among the results of the tests of evaluation of seed physiological quality and the emergence test.

Results and Discussion

The initial evaluation of physiological quality and moisture content of the popcorn seed lots are shown in Table 1. The data referring to moisture content were similar among the popcorn seed lots studied. This is important for carrying out the tests because uniformity of the initial seed moisture content contributes to obtaining consistent results (^{Marcos-Filho, 2015}). Furthermore, ^{Guedes et al. (2011}) emphasized that differences from 1-2% in moisture content among samples do not compromise results and tests can be performed.

Hybrid | Lot | Moisture content | Germination | First count | Emergence |

% | |||||

AP8203 | 1 | 12.9 | 98 a | 96 a | 98 a |

2 | 12.2 | 93 a | 82 b | 89 b | |

3 | 12.7 | 97 a | 94 a | 96 a | |

4 | 11.8 | 85 b | 73 c | 78 c | |

5 | 12.5 | 96 a | 95 a | 97 a | |

CV (%) | 3.3 | 4.0 | 6.2 | ||

AP4512 | 6 | 11.1 | 96 a | 96 a | 96 a |

7 | 12.3 | 98 a | 84 b | 89 b | |

8 | 11.7 | 94 a | 72 c | 75 c | |

9 | 10.9 | 94 a | 73 c | 76 c | |

10 | 11.8 | 97 a | 95 a | 98 a | |

CV (%) | 2.9 | 3.8 | 5.8 |

Mean values followed by the same letter in the column do not statistically differ from each other by the Tukey test at 5% probability.

The germination test showed that lot 4 of the hybrid AP8203 has lower physiological quality, with a statistical difference from the others, i.e., lots 1, 2, 3 and 5 were clustered at the same vigor level and did not differ from each other. The tests of first count of germination and seedling emergence in the field also confirmed that lot 4 was of inferior quality and highlighted lots 1, 3 and 5 as having higher vigor, without a statistical difference from each other. Lot 2 proved to be intermediate.

The results of seed lots of AP4512 hybrid popcorn did not differ from each other in the germination test. However, high and similar results in the germination test do not necessarily mean that all the lots have high vigor, since the germination test is conducted under favorable environmental conditions, allowing the seed lot to express maximum potential for production of normal seedlings (^{Marcos-Filho, 2015}).

For ^{Araujo et al. (2011}), seed lots with similar germination are fundamental for studies that aim to determine the method for evaluation of seed vigor because the aim is to discriminate seed lots with similar levels of germination. If the germination potentials of the seeds show accentuated differences, the germination test itself is able to detect differences in seed physiological potential (^{Marcos-Filho and Novembre, 2009}).

In this respect, the tests of first count of germination and seedling emergence in the field exhibited greater sensitivity, indicating lower physiological quality of the seeds of lots 8 and 9 of the hybrid AP4512. According to ^{Nakagawa (1999}), the first count of the germination test is considered an indication of vigor and it is an important evaluation in identifying seed lots with capacity for faster establishment, and it is conducted at the same time as the germination test.

The emergence test, for its part, is considered the best indicator for making inferences on seed vigor because it should simulate conditions that seeds will be subjected to at the time of sowing in the field (^{Guedes et al., 2011}). Thus, the purpose of the vigor tests is to rank the seed lots, and the lots should be associated with performance of seedlings in the field, so as to monitor the efficiency of the procedures adopted in the laboratory (^{Marcos-Filho, 2015}). These procedures were verified in the studies of ^{Douradinho et al. (2015}) with wheat seeds, and of ^{Catão and Caixeta (2019}) with soybean seeds.

The data obtained for the potassium leaching test of the different popcorn seed lots involving the combinations of number of seeds / water volume / temperature are shown in Tables 2 to 5. At 25 ºC, regardless of using 50 or 100 seeds and varying the water volume (50 or 75 mL), it was not possible to separate the lots into intermediate levels of vigor (Tables 2 and 3). This behavior was also found at 30 ºC using 100 seeds (Table 5). Under these conditions, recommending the potassium leaching test for popcorn seeds would not be viable. However, the use of this test at the temperature of 25 or 30 ºC with water volume of 50 or 75 mL was effective for evaluation of physiological quality of the seed lots of *Mimosa caesalpiniifolia* (^{Avelino et al.; 2018}), *Encholirium spectabile* (^{Araújo and Silva, 2018}), wheat (^{Douradinho et al.; 2015}), and triticale (^{Steiner et al.; 2011}).

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

50 seeds/50 mL/25 ºC | |||||||||

AP8203 | 1 | 425 a | 518 a | 688 a | 721 a | 821 a | 823 a | 932 a | 960 a |

2 | 877 b | 1084 b | 1151 b | 1204 b | 1267 c | 1279 c | 1284 b | 1298 b | |

3 | 463 a | 537 a | 659 a | 736 a | 784 a | 816 a | 905 a | 927 a | |

4 | 470 a | 552 a | 675 a | 793 a | 870 b | 903 b | 981 ab | 1216 b | |

5 | 811 b | 915 b | 976 b | 1054 b | 1232 bc | 1157 bc | 1173 b | 1193 b | |

CV (%) = 3.8 | |||||||||

AP4512 | 6 | 763 a | 839 a | 880 a | 881 a | 893 a | 894 a | 905 a | 965 a |

7 | 1241 b | 1347 b | 1404 b | 1422 b | 1427 b | 1436 b | 1436 b | 1438 b | |

8 | 1608 c | 1676 c | 1735 c | 1758 c | 1812 c | 1819 c | 1819 c | 1822 c | |

9 | 869 ab | 961 ab | 1043 ab | 1064 ab | 1081 ab | 1092 ab | 1092 ab | 1113 ab | |

10 | 674 a | 764 a | 882 a | 879 a | 893 a | 944 a | 944 a | 967 a | |

CV (%) = 4.1 | |||||||||

50 seeds/75 mL/25 ºC | |||||||||

AP8203 | 1 | 371 a | 473 a | 635 a | 674 a | 771 a | 773 a | 889 a | 915 a |

2 | 822 b | 1038 c | 1097 b | 1158 b | 1215 b | 1224 c | 1232 c | 1246 b | |

3 | 418 a | 487 a | 606 a | 686 a | 738 a | 768 a | 857 a | 878 a | |

4 | 420 a | 493 a | 622 a | 744 a | 821 a | 859 b | 936 b | 1162 b | |

5 | 759 b | 865 b | 920 b | 1009 b | 1080 b | 1103 bc | 1120 bc | 1131 b | |

CV (%) = 3.9 | |||||||||

AP4512 | 6 | 714 a | 782 a | 832 a | 834 a | 840 a | 842 a | 854 a | 903 a |

7 | 1198 b | 1298 b | 1353 b | 1369 b | 1372 b | 1378 b | 1386 b | 1389 b | |

8 | 1556 c | 1629 c | 1689 c | 1706 c | 1757 c | 1761 c | 1762 c | 1767 c | |

9 | 811 ab | 907 ab | 995 ab | 1018 ab | 1032 ab | 1033 ab | 1040 ab | 1055 ab | |

10 | 624 a | 714 a | 776 a | 830 a | 833 a | 833 a | 884 a | 914 a | |

CV (%) = 4.3 |

Mean values followed by the same letter in the column do not statistically differ from each other by the Tukey test at 5% probability.

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

100 seeds/50 mL/25 ºC | |||||||||

AP8203 | 1 | 526 a | 652 a | 727 a | 775 a | 830 a | 864 a | 913 a | 916 a |

2 | 715 b | 925 b | 985 b | 1056 b | 1081 b | 1162 b | 1205 b | 1278 b | |

3 | 502 a | 622 a | 696 a | 732 a | 775 a | 797 a | 859 a | 911 a | |

4 | 778 b | 1060 b | 1125 b | 1188 b | 1206 b | 1240 b | 1288 b | 1329 b | |

5 | 499 a | 652 a | 625 a | 719 a | 765 a | 805 a | 851 a | 912 a | |

CV (%) = 4.0 | |||||||||

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

100 seeds/50 mL/25 ºC | |||||||||

AP4512 | 6 | 796 a | 859 a | 862 a | 894 a | 919 a | 944 a | 952 a | 1002 a |

7 | 685 a | 763 a | 827 a | 837 a | 854 a | 899 a | 939 a | 976 a | |

8 | 1398 b | 1496 b | 1510 b | 1512 b | 1525 b | 1535 b | 1568 b | 1584 b | |

9 | 1259 b | 1338 b | 1339 b | 1341 b | 1353 b | 1364 b | 1374 b | 1405 b | |

10 | 750 a | 842 a | 924 a | 930 a | 969 a | 1003 a | 1057 a | 1101 a | |

CV (%) = 3.9 | |||||||||

100 seeds/75 mL/25 ºC | |||||||||

AP8203 | 1 | 493 a | 622 a | 692 a | 736 a | 805 a | 832 a | 849 a | 887 a |

2 | 684 b | 881 b | 951 b | 1025 b | 1057 b | 1128 b | 1168 b | 1243 b | |

3 | 468 a | 590 a | 665 a | 707 a | 740 a | 765 a | 824 a | 881 a | |

4 | 749 b | 1042 b | 1082 b | 1142 b | 1174 b | 1210 b | 1254 b | 1297 b | |

5 | 465 a | 599 a | 626 a | 684 a | 734 a | 772 a | 819 a | 887 a | |

CV (%) = 4.1 | |||||||||

AP4512 | 6 | 765 a | 822 a | 823 a | 866 a | 883 a | 901 a | 911 a | 979 a |

7 | 647 a | 727 a | 790 a | 804 a | 824 a | 852 a | 906 a | 932 a | |

8 | 1353 b | 1455 b | 1484 b | 1489 b | 1492 b | 1496 b | 1532 b | 1555 b | |

9 | 1226 b | 1305 b | 1315 b | 1316 b | 1321 b | 1324 b | 1345 b | 1374 b | |

10 | 729 a | 802 a | 897 a | 901 a | 9355 a | 975 a | 1029 a | 1077 a | |

CV (%) = 4.2 |

Mean values followed by the same letter in the column do not statistically differ from each other by the Tukey test at 5% probability.

Nevertheless, it should be noted that use of the combination of fifty seeds with 50 mL of water at 30 ºC (Table 4) allowed stratification of the popcorn seed lots for both hybrids beginning at 2 hours of soaking. Lot 4 of the AP8203 hybrid was indicated by the potassium leaching test as having the lowest physiological potential. Lots 1, 3 and 5 had the best physiological quality, and lot 2 was classified as intermediate. For the AP4512 hybrid, lots 6 and 10 were classified as having the best physiological potential; lot 7 is intermediate; and lots 8 and 9 have lower performance. These results corroborate the data of the first count of germination test and field emergence test (Table 1).

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

50 seeds/50 mL/30 ºC | |||||||||

AP8203 | 1 | 515 a | 707 a | 792 a | 873 a | 907 a | 974 a | 1041 a | 1176 a |

2 | 891 b | 982 b | 1105 b | 1185 b | 1219 b | 1332 b | 1366 b | 1478 b | |

3 | 486 a | 639 a | 736 a | 805 a | 836 a | 903 a | 979 a | 1065 a | |

4 | 932 b | 1082 b | 1164 b | 1416 c | 1545 c | 1610 c | 1651 c | 1767 c | |

5 | 513 a | 690 a | 761 a | 824 a | 903 a | 947 a | 1035 a | 1109 a | |

CV (%) = 4.3 | |||||||||

AP4512 | 6 | 846 a | 926 a | 935 a | 981 a | 982 a | 994 a | 1124 a | 1168 a |

7 | 1339 b | 1341 b | 1379 b | 1395 b | 1398 b | 1406 b | 1412 b | 1449 b | |

8 | 1515 b | 1608 b | 1613 b | 1621 c | 1635 c | 1651 c | 1729 c | 1746 c | |

9 | 1489 b | 1582 b | 1625 b | 1639 c | 1664 c | 1739 c | 1744 c | 1755 c | |

10 | 828 a | 916 a | 978 a | 1037 a | 1079 a | 1092 a | 1148 a | 1162 a | |

CV (%) = 4.5 | |||||||||

50 seeds/75 mL/30 ºC | |||||||||

AP8203 | 1 | 451 a | 642 a | 734 a | 814 a | 841 a | 912 a | 984 a | 1116 a |

2 | 839 b | 921 b | 1046 b | 1122 b | 1153 b | 1274 b | 1309 b | 1411 b | |

3 | 425 a | 578 a | 671 a | 750 a | 775 a | 845 a | 915 a | 1005 a | |

4 | 888 b | 1036 b | 1110 b | 1155 b | 1183 b | 1257 b | 1292 b | 1409 b | |

5 | 456 a | 638 a | 704 a | 764 a | 848 a | 889 a | 980 a | 1044 a | |

CV (%) = 4.2 | |||||||||

AP4512 | 6 | 782 a | 885 a | 887 a | 927 a | 929 a | 941 a | 1061 a | 1111 a |

7 | 1276 b | 1287 b | 1319 b | 1332 b | 1342 b | 1345 b | 1354 b | 1395 b | |

8 | 1453 c | 1548 c | 1553 c | 1559 c | 1585 c | 1596 c | 1667 c | 1682 c | |

9 | 1220 b | 1226 b | 1269 b | 1285 b | 1310 b | 1374 b | 1384 b | 1393 b | |

10 | 766 a | 853 a | 921 a | 983 a | 1022 a | 1037 a | 1090 a | 1105 a | |

CV (%) = 4.5 |

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

100 seeds/50 mL/30 ºC | |||||||||

AP8203 | 1 | 551 a | 674 a | 740 a | 817 a | 872 a | 914 a | 997 a | 1075 a |

2 | 546 a | 685 a | 777 a | 864 a | 931 a | 1145 b | 11192 b | 1250 b | |

3 | 973 c | 1103 c | 1176 c | 1220 c | 1270 c | 1319 c | 1398 c | 1441 c | |

4 | 827 bc | 944 bc | 1012 bc | 1105 bc | 1165 bc | 1195 bc | 1272 bc | 1312 bc | |

5 | 596 a | 678 a | 744 a | 796 a | 849 a | 888 a | 964 a | 1053 a | |

CV (%) = 4.1 | |||||||||

Hybrid | Lot | Soaking period | |||||||

0.5 | 1 | 1.5 | 2 | 2.5 | 3 | 4 | 5 | ||

100 seeds/50 mL/30 ºC | |||||||||

AP4512 | 6 | 812 a | 875 a | 1036 a | 1037 a | 1079 a | 1095 a | 1156 a | 1159 a |

7 | 1263 b | 1385 b | 1421 b | 1425 b | 1435 b | 1439 b | 1447 b | 1449 b | |

8 | 794 a | 919 a | 967 a | 976 a | 979 a | 995 a | 996 a | 997 a | |

9 | 1407 c | 1518 c | 1565 b | 1568 b | 1572 b | 1576 b | 1579 b | 1585 b | |

10 | 745 a | 864 a | 932 a | 945 a | 975 a | 994 a | 1031 a | 1037 | |

CV (%) = 4.7 | |||||||||

100 seeds/75 mL/30 ºC | |||||||||

AP8203 | 1 | 525 a | 633 a | 709 a | 772 a | 833 a | 878 a | 952 a | 1036 a |

2 | 507 a | 642 a | 736 a | 821 a | 892 a | 1109 b | 1151 b | 1215 b | |

3 | 935 c | 1061 b | 1137 b | 1188 b | 1248 b | 1275 c | 1355 c | 1414 c | |

4 | 789 b | 908 b | 977 b | 1063 b | 1129 b | 1152 bc | 1234 bc | 1278 bc | |

5 | 562 a | 637 a | 701 a | 751 a | 810 a | 841 a | 927 a | 1019 a | |

CV (%) = 4.5 | |||||||||

AP4512 | 6 | 774 a | 871 a | 990 a | 995 a | 1035 a | 1054 a | 1112 a | 1114 a |

7 | 1228 b | 1345 b | 1381 b | 1384 b | 1397 b | 1403 b | 1406 b | 1409 b | |

8 | 760 a | 878 a | 925 a | 933 a | 938 a | 950 a | 955 a | 965 a | |

9 | 1372 c | 1474 c | 1537 c | 1538 c | 1541 c | 1545 c | 1549 c | 1551 c | |

10 | 704 a | 826 a | 896 a | 906 a | 939 a | 958 a | 1013 a | 1034 a | |

CV (%) = 3.9 |

The potassium leaching test also proved to be effective in discriminating the seed lots of sweet corn (*Zea mays* L.) regarding physiological potential (^{Zucareli et al., 2013}). ^{Souza et al. (2014}) also found that seed lots of cotton (*Gossypium hirsutum*) were stratified in two vigor classes (high and low). Thus, determination of this ion by the potassium leaching test has proven to be suitable for evaluation of seed physiological quality (^{Barbieri et al., 2011}).

A big advantage of using the potassium leaching test in evaluation of popcorn seed vigor was its ability to provide fast results. As of two hours, it was already possible to separate the lots into different vigor classes (Table 4). For ^{Marcos-Filho (2015}), determination of differences among seed lots after thirty minutes of soaking is a factor to take into consideration, because this is a big advantage of the potassium leaching test over electrical conductivity, which requires at least 24 hours to make readings. It is also noteworthy that the temperature of 30 °C accelerated leaching of exudates, because, in addition to the temperature, this leaching may be affected by the degree of deterioration, damage to the seed coat, stage of development at the time of harvest, and damage caused by the speed and time of soaking (^{Gonzáles et al., 2011}).

Analysis of the correlation between the data on evaluation of popcorn seed physiological quality and on seedling emergence in the field (Table 6) indicated that the germination test and first count of germination test were positively and significantly (p < 0.05) correlated with seedling emergence, corroborating the results obtained by ^{Araújo and Silva (2018}) and ^{Steiner et al. (2011}) in evaluation of seed lots of *Encholirium spectabile* and triticale, respectively. The results of significant (p < 0.05) and negative correlation between the potassium leaching test and emergence of seedlings in a greenhouse are similar to those found by ^{Douradinho et al. (2015}) and ^{Barbieri et al. (2011}) in wheat and rice seeds, respectively. Thus, as the exudates from potassium leaching increase, the emergence of popcorn seedlings in the field declines.

Hybrid | Test | First count | Potassium leaching | Emergence |

Gemination | 0.983* | -0.897* | 0.955* | |

AP8203 | First count | - | -0.903* | 0.942* |

Potassium leaching | - | - | 0.894* | |

Gemination | 0.927* | -0.915* | 0.932* | |

AP4511 | First count | - | -0.899* | 0.916* |

Potassium leaching | - | - | 0.873* |

*r significant at 5% probability.

In general, for both hybrids, there was significant potassium leaching in the first thirty minutes of soaking of popcorn seeds. However, leaching occurred at lower intensity up to five hours of soaking. This was also confirmed by ^{Zucareli et al. (2013}) in sweet corn seeds. ^{Barbieri et al. (2011}) also found higher potassium leaching readings at 120 minutes of soaking of rice seeds. In short, when seed membranes are directly soaked, they pass from the gel state to the liquid crystalline state (^{Castro et al., 2004}). However, when this transition occurs rapidly, there is not enough time for the membranes to change their structural conformation, and this situation brings about cell damage and electrolyte leaching (^{Silva and Villela, 2011}).