title: Stimulated growth rate by restriction of P availability at moderate salinity but insensitive to P availability at high salinity in Crithmum maritimum.
abstract: The halophyte Crithmum maritimum thrives in cracks of calcareous rocks or cliffs at seashores, a situation which associates limited phosphorus availability and high salinity. In order to understand the common patterns of colonization and zonation of this species, seedlings were cultivated for 34 d in inert sandy soil irrigated with a nutrient solution containing or not phosphorus at moderate (50 mM) or high (250 mM) NaCl level. Net assimilation rate and consequently relative growth rate increased in response to P deprivation at moderate saline level, but not at high salinity level. Parallelly, CO2 fixation rate, rubisco capacity, transpiration rate and stomatal conductance were diminished by P deprivation at moderate NaCl level. Intercellular CO2 concentration was therefore not affected. Chlororophyll fluorescence analysis revealed that photosynthetic systems were insensitive to change in P availability at moderate salinity level: neither pigment content, nor effective and maximum quantum yield, photochemical and non photochemical quenching, and electron transport rate were affected by P deprivation. On the contrary, at high salinity level when net photosynthesis, rubisco capacity and the quantum yields of PS2 were severely affected, P deprivation strongly augmented electron transport rate. Stomatal aperture and more modest increase in net photosynthesis, rubisco capacity, photosystem II effective quantum yield and photochemical quenching accompanied this response. This study shows the tolerance of C. maritimum to the phosphorus deprivation combined to moderate or to high saline level which may explain the common patterns of colonization and zonation of this species.
authors.affiliation: Technopole de Borj Cédria, Laboratoire d'Adaptation des Plantes aux Stress Abiotiques BP901 Hammam, Tunisia. hmidanehla@yahoo.com
authors.forename: Nehla
authors.initials: N
authors.lastname: Labidi
authors.forename: Manel
authors.initials: M
authors.lastname: Ammari
authors.forename: Sana
authors.initials: S
authors.lastname: Snoussi
authors.forename: Najoua
authors.initials: N
authors.lastname: Messelini
authors.forename: Fatma
authors.initials: F
authors.lastname: Gharbi
authors.forename: C
authors.initials: C
authors.lastname: Abdelly
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D010788:Photosynthesis; D045332:Photosystem II Protein Complex; D010858:Pigmentation; D018515:Plant Leaves / Q000187:drug effects; D010944:Plants / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry; D054712:Salinity; D055051:Salt-Tolerant Plants / Q000737:chemistry; D012492:Salts / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D002712:Chlorides; D045332:Photosystem II Protein Complex; D012492:Salts; D002734:Chlorophyll; D002245:Carbon Dioxide; D010758:Phosphorus; D012964:Sodium; D012273:Ribulose-Bisphosphate Carboxylase