Tick ββmarks are not separate objects. They relate to axes and their properties defined by axes.
What you can do is remove label shortcuts and replace them with text objects. In this case, you can control the text properties.
plot(magic(5)) xticks = get(gca,'XTick'); %# x tick positions xlabels = cellstr(get(gca,'XTickLabel')); %# get the x tick labels as cell array of strings set(gca,'XTickLabel',[]) %# remove the labels from axes n = numel(xlabels); yl = ylim; idx1 = 1:2:n; %# 1st set of ticks idx2 = 2:2:n; %# 2nd set t1 = text(xticks(idx1),repmat(yl(1),numel(idx1),1), xlabels(idx1), ... 'HorizontalAlignment','center','VerticalAlignment','top'); t2 = text(xticks(idx2),repmat(yl(1),numel(idx2),1), xlabels(idx2), ... 'HorizontalAlignment','center','VerticalAlignment','top'); set(t2,'FontWeight','bold') %# make the 2nd set bold

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