Photosynthetic gas exchange characteristics in three different almond species during drought stress and subsequent recovery

• Published in: Environmental and experimental botany 2007-03, Vol.59 (2), p.117-129
• Main Authors: Rouhi, V., Samson, R., Lemeur, R., Damme, P. Van
• Format: Article
• Language: English
• Subjects: abscission; almonds; Biological and medical sciences; carbon dioxide; cell respiration; desiccation (plant physiology); drought; Drought avoidance; Drought tolerance; Fundamental and applied biological sciences. Psychology; gas exchange; Intercellular CO 2 concentration; Intrinsic water use efficiency; Leaf abscission; leaves; Metabolism; PEG 6000; photosynthesis; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; Prunus; Prunus dulcis; Prunus lycioides; Prunus scoparia; species differences; stomata; stomatal conductance; water stress; water use efficiency; wild relatives
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2005.10.001

Three different drought stress levels (water potential of the nutrient solution, Ψ s = −0.6, −1.2 and −1.8 MPa, respectively), and a control treatment ( Ψ s = −0.1 MPa), were applied during 2 weeks to three almond species, followed by 3 weeks of recovery. The selected test species were Prunus dulcis (Miller) D.Webb (bitter almond) and two wild almond species, P. lycioides (Spach) C.K. Schneider and P. scoparia (Spach) C.K. Schneider. All three are species native to Iran, and can be used as rootstock, but only P. dulcis is actually used for commercial almond production. In the absence of drought stress, maximum net assimilation rate ( A max) is highest for P. scoparia and lowest for P. dulcis. For all species A max was above 16 μmol CO 2 m −2 s −1. A similar relationship between A max and dark respiration rate ( R d), was observed for all species. This relationship suggests that optimisation of the carbon budget is independent of species. The three investigated species seem to have a different reaction to a similar stress, indicating different drought stress coping strategies. P. scoparia lost all its leaves during the experiment, while P. lycioides only kept some leaves, however, the remaining leaves were almost totally wilted and did not allow for any photosynthesis measurement. P. scoparia did not recover during the experiment, as no new leaves were developed once Ψ s was restored to pre-drought stress levels. However, this species has green stems, indicating that stem photosynthesis might play an important role in the plants’ overall carbon balance. This species is an opportunistic one ( sensu [Higgins, S.S., Larsen, F.E., Bendel, R.B., Radamaker, G.K., Bassman, J.H., Bidlake, W.R., Alwir, A., 1992. Comparative gas-exchange characteristics of potted, glasshouse-grown almond, apple, fig, grape, olive, peach and Asian pear. Sci. Hortic. 52 (4), 313–329]), where assimilation is seriously limited by non-stomatal processes as evidenced by measurements of intercellular CO 2 concentration, eventually resulting in total leaf loss. All P. lycioides leaves almost completely wilted during the experiment, but this species recovered rather quickly. Leaves, newly formed at the end of the experiment, obtained maximal assimilation rates under control Ψ s levels, equivalent to those measured in the control treatment. Finally, P. dulcis did keep at least part of its leaves during drought stress. However, assimilation rates after 2 weeks of drought treatment and 3 weeks o