S11 - Session O3 - Avocado green stems photosynthesis and its relationship with plant hydraulics

Authors: Nadia Valverdi *, Paula Guzmán-Delgado, Camilla Acosta, Gabriella Dauber, Gregory Goldsmith, Eleinis Avila-Lovera

Photosynthesis of green stems in woody plants has the potential to increase plant carbon gain, as well as play an important role in maintaining the hydraulic functioning of plants. Thus, stems of plants that carry out greater rates of photosynthesis could be better at acclimating to, and ultimately surviving, changes in water availability due to climate change. Avocado trees have green stems. Nevertheless, there is little information on avocado green stem photosynthesis and its contribution to plant hydraulics. Hence, the objective of this research was to evaluate stem photosynthesis among different avocado cultivars and its relationship to plant hydraulic functioning. We evaluated variability in stem photosynthetic re-assimilation rate ( A stem ), midday stem water potential ( SWP ), sapwood-specific hydraulic conductivity ( K S ), leaf-specific hydraulic conductivity ( K L ), bark chlorophyll concentration ( Chl a+b ), wood density ( WD ) and contents of non-structural carbohydrates ( NSC ) in twigs of 10 different avocado cultivars growing in a common garden. Our results demonstrate that the green stems of avocado recycle respired CO 2 at rates that vary from 0.2 to 4.8 µmol m -2 s -1 , which corresponds to re-assimilation of 12 to 96 % of CO 2 that would otherwise leave the plant. There were no significant differences in A stem , SWP, WD, or Chl a+b among cultivars. However, there was a significant difference in K L , which indicates greater variability in the capacity of stems to supply water to the leaves. K S and total NSC (bark + wood) also showed differences among cultivars. On the other hand, A stem was not correlated with either K S or K L , but there was a significant relationship between wood and bark NSC contents, supporting the movement of sugars between these two plant tissues. In summary, green stems of avocado re-assimilate CO 2 , contributing to the carbon economy of the plants, although this contribution may not be the primary NSC source for hydraulic functioning.