Abstract
Stem photosynthesis has been suggested to play relevant roles to cope with different biotic and abiotic stress factors, including drought. In the present study, we performed measurements of stem hydraulic conductance and non-structural carbohydrate content in the evergreen Laurus nobilis L. and the deciduous Populusalba L., subjected to inhibition of stem photosynthesis and successive exposure to a drought-recovery cycle in order to check if stem photosynthesis may be involved in allowing hydraulic recovery after drought stress relief. Stem shading affected the growth of L. nobilis but not of P. alba saplings. By contrast, inhibition of stem photosynthesis was coupled to inhibition of hydraulic recovery following embolism build-up under drought in P. alba but not in L. nobilis. The two study species showed a different content and behavior of nonstructural carbohydrates (NSCs). The differences in NSCs’ trend and embolism reversal ability led to a significant relationship between starch content and the corresponding hydraulic conductance values in L. nobilis but not in P. alba. Our findings suggest that stem photosynthesis plays a key role in the maintenance of hydraulic functioning during drought especially in the deciduous species. This, in turn, may increase their vulnerability under current global climate change scenarios.
Highlights
Most terrestrial plants perform photosynthesis at the leaf level, but some of them can only use stems to this purpose, as leaves have been eliminated or transformed into thorns or other organs serving different functions in peculiar habitats
Our findings suggest that stem photosynthesis plays a key role in the maintenance of hydraulic functioning during drought especially in the deciduous species
We focused on two woody species, namely the evergreen Laurus nobilis L. and the deciduous Populus alba L, because, for both of them, there is available experimental evidence suggesting their capacity to reverse xylem embolism following drought stress, with an involvement of nonstructural carbohydrates (NSCs) stores [55,64]
Summary
Most terrestrial plants perform photosynthesis at the leaf level, but some of them can only use stems to this purpose, as leaves have been eliminated or transformed into thorns or other organs serving different functions in peculiar habitats. Photosynthetic activity of stems plays a relevant role to cope with defoliation caused by biotic or abiotic agents [25,26,27]. It contributes to face thermal stress [8,28,29,30,31,32] and drought, as reported in different desert and semi-desert non-succulent species, as well as in Mediterranean plants (i.e., [4,5,8,10,11,12,33,34])
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