Because air inside leaf is saturated when a leaf is hot, air inside leaf holds more water, increasing the concentration gradient from inside to the outside of the leaf. As we saw earlier when we looked at photosynthesis, photosynthetic pathways like C4 has higher WUE than C3. CAM is very water-efficient 6. As we saw when we looked at cavitation, many conifers and desert plants have tracheids or small-diameter xylem vessels that prohibit cavitation under extremely low Y w. Most of these species also have smaller pores in the pit membranes between vessels.
Smaller pores reduce the chance that embolisms are introduced into vessels.
In addition, they often have more pits in xylem vessels, which ensure that vessels are refilled and hydraulic connectivity is restored following cavitation. Interestingly, the stem can store some water. This buffers transpiration from water uptake. It occurs mainly in live parenchyma cells with non-lignified walls. Trees shrink in diameter at midday.