INFLUENCE OF INITIATION AND PRODUCTION OF STOLONS AND TUBERS BY ETHEPHONE

In four-year experiment conducted during the vegetation period, the nu mber of growing stolons, including bending ones, stolons with initiate d tubers, the weight of all stolons and the number of branches of stol ons after the treatment of stand with ethephone (CEPA) were studied. D uring the vegetation the maximum weight of tops and after the physiolo gical maturity, the number and the weight pf tubers in two varieties o f potatoes (Karin - early, table; Kamyk - late, for commercial use) gr owing on two nitrogen levels (80 and 120 kg N.ha(-1)), were estimated. Ethephone was applied in the concentration of 0.05 and 0.1 % to the s tand in the bud phase to the onset of anthesis after the fourth sampli ng. For every hill 10 ml of solution was applied. The treatment with C EPA had not marked influence on the stolen number in the phase of thei r initial growth to the length, or in the finished growth in the phase of bending stolons (Fig. 1). Unambiguous positive influence of CEPA w as estimated until in arised stolons, on whose ends was the beginning of the tubers initiation (Fig. 2). Between both used concentrations th ere were no (with some exceptions) great differences in the number of stolons, greater differences were recorded between them and the number of stolons in control plants. The known effect of the increase of inh ibiting substances in stolons, that precedes the tubers production and the possibility of increase of tuberization was confirmed using the e xogen inhibitor, CEPA in this case. The weight of stolons corresponded well during the greater part of vegetation to the level of ethephone. The greatest weight of stolons was found in the application of 0.1 % CEPA, the cower weight was in stolons after the treatment with a half concentration (0.05 %) and the lowest weight of stolons had control pl ants (Fig. 3). Stolons of variety Karin had a double weight in the com parison with stolons of the variety Kamyk. Differences between stolons of treated and control plants were higher in the variety Karin. There are not only statistically significant differences of the weight of s tolons between varieties but also a different variety reaction after t he treatment with ethephone. Varietal differences were observed also i n the number of growing and bending stolons and also in the number of stolons with initiated tubers. These values were higher in the variety Kamyk, but the difference in the weight of stolons was opposite. In a ny case CEPA influenced positively the number and the weight of stolon s. At higher level of nitrogen (120 kg N.ha(-1)), higher values of exa mined factors were obtained and differences between stolons of treated and control plants were higher at this nitrogen level. This was also the case of stolen branching, when the variety Karin possessed the num ber of branches approximately 10 to 12 times higher opposed to the var iety Kamyk (Fig. 4).