Water-use efficiency is higher in green stems than in leaves of a tropical tree species
- 143 Downloads
Stems have similar photosynthetic rates as leaves but higher water-use efficiency.
Plants with green photosynthetic stems are common in sub-tropical and tropical dry woodlands worldwide, yet the benefits of photosynthetic stems in tropical species have not been studied before. Parkinsonia praecox (Ruiz & Pav. ex Hook.) Hawkins (Fabaceae) is a small tree found in the arid and semi-arid regions of northern Venezuela and has green stems. We evaluated ecophysiological traits and the role of the photosynthetic stem in the carbon gain of P. praecox in a tropical dry forest, by measuring seasonal changes in water status, gas exchange, water-use efficiency (WUE), photochemical activity of PSII, and biochemical, morphometric and functional traits of leaves and green stems. We found stem net photosynthesis with a rate of 17 µmol m−2 s−1, indicating that the stem contribution to the carbon balance of the species is positive. We also found 1.6 and 2.5 times higher instantaneous and intrinsic WUE, respectively, in green stems than in leaves during the rainy season, which has important implications for water balance. Drought had a negative effect on water potential, leaf PN and photochemical activity of the stem. A similar contribution to the daily whole-plant carbon gain by each photosynthetic organ was found during both seasons; however, when leaf loss is complete during the dry season, the stem contribution would increase up to 100%.
KeywordsCarbon balance Carbon isotope composition Drought Gas exchange Stem net photosynthesis Water loss
We want to thank Jenny De Almeida, Rosa Urich, Ilsa Coronel, Oranys Marín and Carolina Kalinhoff for help provided in the field. Special thanks to Luis Hermoso for his help with the anatomical sections, and Miquel Gonzalez-Meler for his help with the carbon isotope data. We also thank Ana Herrera for helpful discussions that improved this manuscript.
This study was funded by Universidad Central de Venezuela Consejo de Desarrollo Científico y Humanístico (PI 03-7458-2009 and PG 03-7635-2009 to WT).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights statement
This research did not involve human participants and animals.
- Adams M, Strain B (1968) Photosynthesis in stems and leaves of Cercidium floridum—spring and summer diurnal field response and relation to temperature. Oecol Plant 3:285–297Google Scholar
- Ávila E, De Almeida J, Tezara W (2014a) Comparación ecofisiológica y anatómica de los tejidos fotosintéticos de Cercidium praecox (Ruiz & Pav. ex Hook.) Harms (Fabaceae, Caesalpinioideae). Acta Bot Venezuelica 37:59–76Google Scholar
- Bruinsma J (1963) The quantitative analysis of chlorophylls a and b in plant extracts. Photochem Photobiol 2:241–249. https://doi.org/10.1111/j.1751-1097.1963.tb08220.x CrossRefGoogle Scholar
- Farquhar G, Richards R (1984) Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Funct Plant Biol 11:539–552Google Scholar
- Farquhar GD, Sharkey TD (1982) Stomatal conductance and photosynthesis. Annu Rev Plant Physiol 33:317–345. https://doi.org/10.1146/annurev.pp.33.060182.001533 CrossRefGoogle Scholar
- Farquhar GD, O’leary MH, Berry JA (1982) On the relationship between carbon isotope discrimination and the intercellular carbon dioxide concentration in leaves. Funct Plant Biol 9:121–137Google Scholar
- Herrera A, Cuberos M (1990) Stomatal size, density and conductance in leaves of some xerophytes from a thorn scrub in Venezuela differing in carbon fixation pathway. Ecotropicos 3:67–76Google Scholar
- Krall JP, Edwards GE (1992) Relationship between photosystem II activity and CO2 fixation in leaves. Physiol Plant 86:180–187. https://doi.org/10.1111/j.1399-3054.1992.tb01328.x CrossRefGoogle Scholar
- Lawlor DW (1995) The effects of water deficit on photosynthesis. In: Smirnoff R (ed) Environment and plant metabolism: flexibility and acclimation. BIOS Scientific Publishers, Oxford, pp 129–160Google Scholar
- Lindorf H, de Parisca L, Rodríguez P (2006) Botanica. Clasificación, estructura, reproducción, 2nd edn. Ediciones de la Biblioteca de la Universidad Central de Venezuela, VenezuelaGoogle Scholar
- Tezara W, Urich R, Coronel I et al (2010) Asimilación de carbono, eficiencia de uso de agua y actividad fotoquímica en xerófitas de ecosistemas semiáridos de Venezuela. Ecosistemas 19:67–78Google Scholar