One degree matters:
http://www.eea.europa.eu/cop15/bend-the-trend/one-degree-matters-movie

Phloem loading:
- http://www.sciencedaily.com/releases/2007/12/071221163216.htm
Sugar transport driven by polymerisation of sucrose molecules in leaves. If sucrose backs up, photosynthesis is paused/slowed down. Therefore, accelerating sucrose polymerisation could lead to faster ps rates