Can a mirror reflect photons present in sunlight? If yes, do plants absorb these reflected photons or do they need direct sunlight?

I wondered about the same for quite a few years...then I gave up :( Well, I'll try to redeem myself..somewhat Now no surface is 100% ideal..i.e. - no mirror will reflect 100% of all the radiation it receives. There will be absorption by the mirror material and negligible transmittance, too. Now, factor in the emissivity of the mirror surface- the amount of radiation it can give back from whatever meager incident radiation it received. Further, add up the scattering and dispersion due to the extra distance you are making the beam travel- from the source to the mirror to the plant...Some more is lost due to the angles and absorption coefficient.. So, to sum up, I reckon that it all depends on the energy of the photon.. I could provide an analogy (albeit in a roundabout manner) - glasshouses used in polar regions for growing flora... the glasses allow particular IR inside while filtering out the rest, on account of the transmittance factor of glass... Since mirrors maybe assumed to have negligible transmittance,... so I guess direct sunlight is required, unless u use glass or some translucent/ transparent material !!

A decent metal mirror preserves all the properties of incoming light that plants care about, except that it wastes a tiny amount of intensity - typically 2–3%.