Some cycads attract pollinators using heat

"Plants usually attract pollinators using bright colors and scents, but some of the earliest plants use heat instead. A collaboration between professor of molecular and cellular biology Nicholas Bellono and Hessel professor of biology Naomi Pierce has shown that cycads, a division of cone-bearing plants that are ancient in evolutionary terms, warm their reproductive structures in daily cycles, releasing invisible infrared radiation that attracts beetle pollinators. 

Experiments showed that beetles are drawn to this heat even when color, scent, and touch are removed, proving that infrared radiation itself acts as a signal. The team also discovered that the cycad-feeding beetles have specialized sensory cells in their antennae that detect infrared heat, tuned precisely to the temperatures produced by their host plants. 

This heat-based signaling predates colorful flowers and likely played a key role in the earliest plant-pollinator relationships, long before bees and butterflies became dominant."

I find this fascinating.  The fact that plants can generate heat is not novel, as anyone familiar with skunk cabbage melting snow in the spring understands, and I suppose some modern plants can be warmer than their environment based on dark colored leaves absorbing solar energy, but all of this cycad science is new to me.  How do plants generate infrared radiation?  Maybe they just selectively reflect infrared radition from sunlight?  

Text and image (cropped for size) from Harvard Magazine.   I have not found the primary source publication, which is probably in Nature or Science, but I don't have time to search today.

Addendum:  Found the journal article in Science, but it's behind a paywall.