Excess of light without excess of heat

[DavTom]

Hi,

What happens to orchids if they are exposed to an excess of light without an excess of heat?

Nowadays leds have become so efficient that you can easily provide an excess of light without having an excess of heat.

I have a mini growing tent (actually it is a stealth grow area within a small cupboard) in which I have a temperature between 26-28 degrees Celsius with lights ON and a temperature between 19-21 degrees Celsius with lights OFF.

When the lights are ON, the leaves have usually a temperature of about 1-degree Celsius higher than the temperature inside the cupboard (maybe the transpiration is not optimal as I read that the temperature of the leaves should be equal or lower than the ambient temperature? or maybe it is normal as my light has also infrared LEDs that provide some extra heat...).

Anyway, I am providing Phals with 200-250 PAR, Bulbs and Dendr with 300 PAR, and Cattleya with 400 PAR. Lights are ON for 14 hours x day. I understand that this is (significantly?) above optimal PAR and DLI for these orchids, right?

I have searched the web without finding any conclusive info about what happens to orchis exposed to an excess of light without an excess of heat.

Maybe somebody in this forum has some experience with that?

Thanks in advance.

Dav