Study of Spent Coffee Grounds Using Cytological Technique on Root Tip of Allium cepa

Coffee is a widely consumed beverage that has a major impact on economies, markets, and industries; however, the postproduction of coffee drinks results in wasted or spent coffee grounds (SCG). SCG is used as a plant growth medium; however, its suitable level of use is uncertain. This research determined the optimal amount of SCG for root development and its effect on the cells of Allium cepa. The SCG was mixed with sand (S) in different ratios (SCG:S = 40:60, 50:50, 60:40, 70:30, 80:20, 90:10) to evaluate their effects on root growth and cytotoxicity on cells. Root number and length were measured to assess growth, while the mitotic index (MI) and chromosomal abnormalities were analyzed to determine cytotoxic effects. The 40:60 SCG:S mixture produced the highest root growth compared to controls, whereas higher SCG ratios (70:30, 80:20, 90:10) reduced the MI. Various chromosomal abnormalities were observed, such as micronuclei, c-mitosis, fragmented chromosomes, chromosome bridges, sticky chromosomes, and laggard chromosomes. Therefore, the chemical compounds in SCG affected cytotoxicity on A. cepa roots. The most beneficial use of SCG for addition to plant growth media resulted from a precisely defined mixture to balance growth enhancement with potential cytotoxic risk.