I used this procedure

1 mL of buffer solution(0.2 M Tris.HCl, 4 mM MgCl2.6H2O, 2 mM EDTA Na2.2H2O, 86 mM NaCl, 10 mM sodium metabisulfite, 1 % PVP-10, 1 %(v/v) Triton X-100, pH 7.5) was added to a Petri dish containing the plant tissue, which was chopped using a sharp razor blade for approx. 60 s.The resulting homogenate was filtered through an 80-mm nylon filter to remove large debris. Nuclei were stained with 50 mg/ml propidium iodide and 50 mg/mL RNase

However all I could see after this is background in flowcytometer so please suggest a another method or improvements in the same protocol