My programmable Xbee starts receiving after a certain delay although the Tx starts transmission. What is the problem?

Could it be that you have not accounted for the Rout Discovery process that needs to occur before the data packet is actually sent? All of the XBee mesh products need to do this.

i am getting the delay in reception of data even after the node gets discovered.i successfully receive the Transmitter nodes address on the receiver terminal but further i am unable to receive the data immediately, it starts after a delay of 10-15 minutes.What could be the possible reason for this???

Unless you are using a Long sleep period on the radio, they are not capable of causing this type of latency or delay. I would suggest taking the radios out of the picture for now and just get it working under a wired connection. This way you can take some unknowns out of the situation and get it working under a cabled connection first.

Neither the sleep period period is large its about 5 sec only…!!! Simply using XCTU for transmission and reception i am not able to receiver perfectly…!!! what could be the other possible reason behind this large latency ???

I am sorry but are you saying that with XCTU, you are NOT able to reproduce the issue between the two modules?