Morphological and Physiological Responses of Hawaiian Hibiscus tiliaceus Populations to Light and Salinity

Abstract

Hibiscus tiliaceus (Hau) is a pantropical mangrove associate that usually occurs in coastal ecosystems where substrate salinity is relatively high, but it also inhabits upland habitats in Hawaii. Cuttings from three populations on the island of Oahu, Hawaii, were collected and grown in the glasshouse under two levels of substrate salinity (0 and 335 mOsm kg-1) and three light treatments (0%, 50%, and 90% shade). Photosynthetic gas exchange, biomass allocation, and accumulation were studied in relation to salinity and light. Salinity reduced net CO2 assimilation in the upland population but had no effect or stimulated photosynthesis in the coastal populations, whereas increasing salinity decreased stomatal conductance in all populations and therefore increased water-use efficiency. The degree to which photosynthesis was inhibited by salinity was inversely proportional to the salinity of the source population, indicating a loss of salinity tolerance in upland plants. Light had a stronger effect on leaf area ratio (LAR) and leaf mass per area (LMA), whereas salinity had a stronger effect on leaf water content, internode length, and plant biomass. Salinity reduced total new biomass by 58%, 50%, and 34% in full sun, 50% shade, and 90% shade, respectively, but this response did not differ between populations. Salinity reduced the photosynthesis, but not growth, of upland plants because increased allocation to photosynthetic tissue increased LAR to compensate for inhibition of photosynthesis by salinity.

Effet de la salinité sur la croissance des deux variétés de bananier « grande naine » et « petite naine » et leur nutrition minérale au Maroc

“…Photo 1a : Effet du NaCl sur la biomasse aérienne chez la petite naine Photo 1b: Effet du NaCl sur la biomasse racinaire chez la grande naine Cette réduction peut être liée à des perturbations de concentrations des régulateurs de croissance (acide abscissique et cytokinines comme décrit par Termaat et al 1985et Kuiper et al 1990., mais aussi à une réduction de la capacité photosynthétique suite à une diminution de la conductance stomatique du CO2 induite par la contrainte saline (Walker et al1981 ;Santiago et al ;2000). Chez Citrus aurantium, cette réduction de croissance serait principalement due à l'effet osmotique de la salinité (Ruiz et al 2001).…”

The Phi Thickening in Roots of Broccoli Plants: An Acclimation Mechanism to Salinity?

“…Salinity stress also affects the stomatal conductance (G S ) (Goldstein et al 1996;Santiago et al 2000;Djanaguiraman et al 2006). Bayuelo-Jiménez et al (2003) reported a decreased G S in Phaseolus plants grown under salinity because of a toxic effect of Na + and Cl À ; apart from this, higher concentrations of these ions were capable of reducing CO 2 assimilation.…”

NaCl stress causes changes in photosynthetic pigments, proteins, and other metabolic components in the leaves of a true mangrove,Bruguiera parviflora, in hydroponic cultures

“…This family of mangrove has a viviparous mode of germination and is tolerant to changes in salinity gradients. *Corresponding author; fax +91-674-550274 e-mail a b das@hotmaiI.comThe effects of salt on mangroves have been studied in relation to their leaf structure and their rates of transpiration, stomatal conductance, and photosynthesis (Lovelock et al, 1992;Moorthy and Kathiresan, 1999;Theuri et al, 1999;Santiago et al, 2000). Recently, Tanaka et al (2000) reported that the Na § § antiporter catalyzes the exchange of Na § for H § across the vacuolar membrane of cells in Bruguiera sexangula.…”