METODĂ ANALITICĂ DE DETERMINARE A pH-ULUI SUCULUI CELULAR AL FRUNZELOR SPECIILOR POMICOLE ANALYTICAL METHOD FOR THE DETERMINATION OF THE CELLULAR JUICE pH IN FRUIT TREE SPECIES LEAVES Mihaela Lungu Institutul de Cercetări pentru Pedologie şi Agrochimie, Bucureşti SUMMARY The pH of the cellular juice of the fruit tree species enables the diagnosis of nutritional disorders before their characteristic symptoms show up. Therefore, the elaboration of a sure, precise, rapid and cheap method for pH determination is important. The following factors have been considered, which may influence the determined values of the cellular juice pH: the sampling period, the fruit tree species (variety-father plant), the analytical method. The leaves were sampled at three different phenological phases; seven fruit tree species were studied; three analytical methods were used. The sampling and the analyses were carried out in three replications. Finally, a method was proposed to be used, which is the most efficient and best describes the studied chemical feature. The cellular juice pH of the fruit tree species leaves could be used as a naturally or antropically induced nutritional disorders indicator. Key words: pH, cellular juice, analytical method INTRODUCERE pH-ul sucului celular al frunzelor speciilor pomicole permite diagnosticarea unor dereglări de nutriţie înainte de apariţia simptomelor caracteristice acestora. Este importantă, de aceea, elaborarea unei metode sigure, precise, rapide şi ieftine de determinare a acestei caracteristici chimice. O metodă de diagnosticare a clorozei ferice, la speciile pomicole de pe solurile carbonatice (Voiculescu, 1993), are la bază stabilirea existenţei unei corelaţii între pH- ul sucului celular al frunzelor şi puterea de clorozare a solurilor carbonatice. pH-ul citoplasmei este determinat de concentraţia ionilor de hidrogen. În timpul zilei, când predomină procesul de fotosinteză, se produce scăderea pH-ului, datorită