AOBPreview originally published online on October 8, 2003
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Annals of Botany 92: 757-765, 2003
© 2003 Annals of Botany Company
Photosynthetic Responses of the Tropical Spiny Shrub Lycium nodosum (Solanaceae) to Drought, Soil Salinity and Saline Spray
1 Centro de Botánica Tropical, Instituto de Biología Experimental, Universidad Central de Venezuela, Apartado 47577, Caracas 1041-A, Venezuela and 2 Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas 1020-A, Venezuela
* For correspondence. E-mail wtezara{at}strix.ciens.ucv.ve
Received: 26 June 2003; Returned for revision: 28 July 2003; Accepted: 20 August 2003 Published electronically: 8 October 2003
Water relations and photosynthetic characteristics of plants of Lycium nodosum grown under increasing water deficit (WD), saline spray (SS) or saline irrigation (SI) were studied. Plants of this perennial, deciduous shrub growing in the coastal thorn scrubs of Venezuela show succulent leaves which persist for approx. 1 month after the beginning of the dry season; leaf succulence is higher in populations closer to the sea. These observations suggested that L. nodosum is tolerant both to WD and salinity. In the glasshouse, WD caused a marked decrease in the xylem water potential (
), leaf osmotic potential (s) and relative water content (RWC) after 21 d; additionally, photosynthetic rate (A), carboxylation efficiency (CE) and stomatal conductance (gs) decreased by more than 90 %. In contrast, in plants treated for 21 d with a foliar spray with 35 
NaCl or irrigation with a 10 % NaCl solution, and RWC remained nearly constant, while s decreased by 30 %, and A, CE and gs decreased by more than 80 %. An osmotic adjustment of 0·60 (SS) and 0·94 MPa (SI) was measured. Relative stomatal and mesophyll limitations to A increased with both WD and SS, but were not determined for SI-treated plants. No evidence of chronic photoinhibition due to any treatment was observed, since maximum quantum yield of PSII, Fv/Fm, did not change with either drought in the field or water or salinity stress in the glasshouse. Nevertheless, WD and SI treatments caused a decrease in the photochemical (qP) and an increase in the non-photochemical (qN) quenching coefficients relative to controls; qN was unaffected by the SS treatment. The occurrence of co-limitation of A by stomatal and non-stomatal factors in plants of L. nodosum may be associated with the extended leaf duration under water or saline stress. Additionally, osmotic adjustment may partly explain the relative maintenance of A and gs in the SS and SI treatments and the tolerance to salinity of plants of this species in coastal habitats.
Key words: Drought, Lycium nodosum, fluorescence, mesophyll limitation, saline stress, stomatal limitation, water deficit.
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