Dear:

it is said Rho is positively related to Call Option and negatively related to put option. To my knowlege, the price of Call or Put is just the discount value of payoff thru the binomial model, so Rho is the risk free rate and in the denominator, it should have and negatively related to both call/put. I mean when the Rate is high/low the Call/Put should be low/high respectively.

Thanks