Tezara Wilmer, Martínez Dayag, Rengifo Elizabeth, Herrera Ana
Centro de Botánica Tropical, Instituto de Biología Experimental, Universidad Central de Venezuela, Apartado 47577, Caracas 1041-A, Venezuela.
Ann Bot. 2003 Dec;92(6):757-65. doi: 10.1093/aob/mcg199. Epub 2003 Oct 8.
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 (psi), leaf osmotic potential (psi(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 per thousand NaCl or irrigation with a 10 % NaCl solution, psi and RWC remained nearly constant, while psi(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.
研究了在水分亏缺（WD）增加、盐雾（SS）或盐灌（SI）条件下生长的枸杞（Lycium nodosum）植株的水分关系和光合特性。这种多年生落叶灌木生长在委内瑞拉沿海多刺灌丛中，其叶片肉质化，在旱季开始后约持续1个月；靠近海洋的种群叶片肉质化程度更高。这些观察结果表明，枸杞对水分亏缺和盐分均具有耐受性。在温室中，水分亏缺处理21天后，木质部水势（ψ）、叶片渗透势（ψs）和相对含水量（RWC）显著降低；此外，光合速率（A）、羧化效率（CE）和气孔导度（gs）下降超过90%。相比之下，用35‰ NaCl进行叶面喷施或用10% NaCl溶液灌溉处理21天的植株，ψ和RWC几乎保持不变，而ψs下降了30%，A、CE和gs下降超过80%。测得渗透调节值分别为0.60（盐雾处理）和0.94 MPa（盐灌处理）。随着水分亏缺和盐雾处理，气孔和叶肉对光合速率的相对限制增加，但未对盐灌处理的植株进行测定。未观察到因任何处理导致慢性光抑制的证据，因为PSII的最大量子产量Fv/Fm在田间干旱或温室水分或盐分胁迫下均未发生变化。然而，与对照相比，水分亏缺和盐灌处理导致光化学猝灭系数（qP）下降，非光化学猝灭系数（qN）增加；盐雾处理对qN无影响。枸杞植株中光合速率受气孔和非气孔因素共同限制的现象，可能与水分或盐分胁迫下叶片持续时间延长有关。此外，渗透调节可能部分解释了盐雾和盐灌处理下光合速率和气孔导度的相对维持以及该物种植株在沿海生境中对盐分的耐受性。
