This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. of or relating to phototaxis

In botany, pertaining to, characteristic of, or exhibiting phototaxis.

In biology, of or pertaining to the locomotion of organisms in relation to direction of light; exhibiting phototaxis or photopathy.

"Unlike other algae genera sequenced to date, these swift swimmers can cut through the water column at a rate of 50 body lengths per second, and are phototactic, meaning that they can swim towards the sunlight from which they derive their energy."