Adding a horizontal line to a plot

Im trying to add a line at y=0 through the root of the function but for some reason I cant get it to work. This is what I have. If anyone could help that would be great.

f1=@ (x) exp(.5.*x)-sqrt(x)-3;
p01r=fzero(f1,3.1)
c=[0:5];

figure
fplot(f1,[1 5]);
hold on
plot(3.1236,0,'or');
plot(c,0);
hold off

Answer 1

[Matt J]

 plot(c, zeroes(size(c)))