JXB Advance Access originally published online on September 15, 2006
Journal of Experimental Botany 2006 57(14):3697-3706; doi:10.1093/jxb/erl121
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Salinity tolerance of ‘Valencia’ orange trees on rootstocks with contrasting salt tolerance is not improved by moderate shade
1University of Florida, IFAS, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
2Universidad de Córdoba. Dpto. Agronomía, Apdo. 3048, E-14080 Córdoba, Spain
3Centro de Edafologia y Biologia Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Espinardo, E-30100 Murcia, Spain
* To whom correspondence should be addressed. E-mail: JMSN{at}ufl.edu
The effects of shading in combination with salinity treatments were studied in citrus trees on two rootstocks with contrasting salt tolerance to determine if shading could reduce the negative effects of salinity stress. Well-nourished 2-year-old ‘Valencia’ orange trees grafted on Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive), were grown either under a 50% shade cloth or left unshaded in full sunlight. Half the trees received no salinity treatment and half were salinized with 50 mM Cl– during two 9 week salinity periods in the spring and autumn interrupted by an 11 week rainy period. The shade treatment reduced midday leaf temperature and leaf-to-air vapour pressure deficit regardless of salinity treatments. In non-salinized trees, shade increased midday CO2 assimilation rate (ACO2) and stomatal conductance, but had no effect on leaf transpiration (Elf). Shade also increased leaf chlorophyll and photosynthetic water use efficiency (ACO2/Elf) in leaves on both rootstocks and increased total plant dry weight in Cleo. The salinity treatment reduced leaf growth and leaf gas exchange parameters. Shade decreased Cl– concentrations in leaves of salinized Carr trees, but had no effect on leaf or root Cl– of trees on Cleo. There were no significant differences in leaf gas exchange parameters of shaded and unshaded salinized plants but the growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na+ than unshaded trees after the first salinity period, and this shade-induced elevated leaf Na+ persisted after the second salinity period in trees on Carr. Thus, shading did not alleviate the negative effects of salinity on growth and Na+ accumulation.
Key words: Cl–, CO2 assimilation, Na+, stomatal conductance, water use efficiency
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. G. Perez-Perez, J. P. Syvertsen, P. Botia, and F. Garcia-Sanchez Leaf Water Relations and Net Gas Exchange Responses of Salinized Carrizo Citrange Seedlings during Drought Stress and Recovery Ann. Bot., August 1, 2007; 100(2): 335 - 345. [Abstract] [Full Text] [PDF]
|
|