Is green stem photosynthesis in avocado related to plant hydraulics?

N.A. Valverdi, P. Guzmán-Delgado, C. Acosta, G.R. Dauber, K.B. Cooper, G.R. Goldsmith, E. Ávila-Lovera
Photosynthesis occurring in green stems of woody plants may play important roles in plant water and carbon balances. We evaluated the variability in stem photosynthetic re-assimilation rate (Astem), midday stem water potential (Ѱstem, midday), sapwood-specific hydraulic conductivity (KS), leaf-specific hydraulic conductivity (KL), bark chlorophyll concentration (Chla+b), wood density (WD) and concentrations of non-structural carbohydrates (NSC) in twigs of 10 different avocado cultivars growing in a common garden. Our results demonstrate that green stems of avocado plants recycle respired CO2 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 CO2 that would otherwise leave the branch. Cultivars had no significant differences in Astem, Ѱstem, midday, WD, or Chla+b. However, there was a significant difference in KL, which indicates greater variability in the capacity of stems to supply water to the leaves. KS and total NSC (bark + wood) also showed differences among cultivars. Astem was not correlated with either KS or KL, but there was a significant relationship between wood and bark NSC concentrations, supporting the movement of sugars between these two plant tissues. In summary, green stems of avocado re-assimilate CO2, contributing to the carbon economy of the plants, although this contribution may not be the primary NSC source for hydraulic functioning.
Valverdi, N.A., Guzmán-Delgado, P., Acosta, C., Dauber, G.R., Cooper, K.B., Goldsmith, G.R. and Ávila-Lovera, E. (2023). Is green stem photosynthesis in avocado related to plant hydraulics?. Acta Hortic. 1372, 129-136
DOI: 10.17660/ActaHortic.2023.1372.17
bark, drought, hydraulic conductivity, non-structural carbohydrates, plant stems

Acta Horticulturae