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Physiological and anatomical changes induced by drought in two olive cultivars (cv Zalmati and Chemlali)

100%

Boughalleb F., Hajlaoui H.

Acta Physiologiae Plantarum

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2011

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tom 33

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nr 1

Photosynthetic gas exchange, vegetative growth, water relations and fluorescence parameters as well as leaf anatomical characteristics were investigated on young plants of two Olea europaea L. cultivars (Chemlali and Zalmati), submitted to contrasting water availability regimes. Twoyear-old olive trees, grown in pots in greenhouse, were not watered for 2 months. Relative growth rate (RGR), leaf water potential (ΨLW) and the leaf relative water content (LWC) of the two cultivars decreased with increasing water stress. Zalmati showed higher values of RGR and LWC and lower decreased values of ΨLW than Chemlali, in response to water deficit, particularly during severe drought stress. Water stress also caused a marked decline on photosynthetic capacity and chlorophyll fluorescence. The net photosynthetic rate, stomatal conductance, transpiration rate, the maximal photochemical efficiency of PSII (Fv/Fm) and the intrinsic efficiency of open PSII reaction centres (F'v/F'm) decreased as drought stress developed. In addition, drought conditions, reduced leaf chlorophyll and carotenoids contents especially at severe water stress. However, Zalmati plants were the less affected when compared with Chemlali. In both cultivars, stomatal control was the major factor affecting photosynthesis under moderate drought stress. At severe drought-stress levels, the non-stomatal component of photosynthesis is inhibited and inactivation of the photosystem II occurs. Leaf anatomical parameters show that drought stress resulted in an increase of the upper epidermis and palisade mesophyll thickness as well as an increase of the stomata and trichomes density. These changes were more characteristic in cv. ‘Zalmati’. Zalmati leaves also revealed lower specific leaf area and had higher density of foliar tissue. From the behaviour of Zalmati plants, with a smaller reduction in relative growth rate, net assimilation rate and chlorophyll fluorescence parameters, and with a thicker palisade parenchyma, and a higher stomatal and trichome density, we consider this cultivar more droughttolerant than cv. Chemlali and therefore, very promising for cultivation in arid areas.

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Anatomical changes induced by increasing NaCl Salinity in three fodder shrubs, Nitraria retusa, Atriplex halimus and Medicago arborea

80%

Boughalleb F., Denden M., Tiba B. B.

Acta Physiologiae Plantarum

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2009

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tom 31

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nr 5

Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Plants were harvested after 120 days of salt-treatment. The present study was designed to study the effect of salinity on root, stem and leaf anatomy, water relationship, and plant growth in greenhouse conditions. Salinity induced anatomical changes in the roots, stems and leaves. The cuticle and epidermis of N. retusa and A. halimus stems were unaffected by salinity. However, root anatomical parameters (root cross section area, cortex thickness and stele to root area ratio), and stem anatomical parameters (stem cross section area and cortex area) were promoted at 100–200 mM NaCl. Indicating that low to moderate salinity had a stimulating effect on root and stem growth of these xero-halophytic species. At higher salinities, root and stem structures were altered significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea, they were strongly altered as salinity rose. NaCl (100–300 mM) reduced leaf water content by 21.2–56.2% and specific leaf area by 51–88.1%, while increased leaf anatomical parameters in M. arborea (e.g. increased thickness of upper and lower epidermis, palisade and spongy mesophyll, entire lamina, and increased palisade to spongy mesophyll ratio). Similar results were evidenced in A. halimus leaves with salinity exceeding 100 mM NaCl. Leaves of N. retusa were thinner in salt-stressed plants while epidermis thickness and water content was unaffected by salinity. The size of xylem vessel was unchanged under salinity in the leaf’s main vein of the three species while we have increased number in M. arborea leaf main vein in the range of 200–300 mM NaCl. A longer distance between leaf vascular bundle, a reduced size and increased number of xylem vessel especially in stem than in root vascular system was evidenced in M. arborea treated plants and only at (400–800 mM) in the xero-halophytic species. The effects of NaCl toxicity on leaf, stem and root ultrastructure are discussed in relation to the degree of salt resistance of these three species. Our results suggest that both N. retusa and A. halimus show high tolerance to salinity while M. arborea was considered as a salt tolerant species.

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Photosystem II photochemistry and physiological parameters of tree fodder shrubs, Nitraria retusa, Atriplex halimus and Medicago arborea under salt stress

80%

Boughalleb F., Denden M., Tiba B. B.

Acta Physiologiae Plantarum

|

2009

|

tom 31

|

nr 3

Nitraria retusa and Atriplex halimus (xerohalophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Salt stress caused a marked decrease in osmotic potential and a significant accumulation of Na⁺ and Cl⁻ in leaves of both species. Moderate salinity had a stimulating effect on growth rate, net CO₂ assimilation, transpiration and stomatal conductance for the xero-halophytic species. At higher salinities, these physiological parameters decreased significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea they decreased linearly with salinity. Nitraria retusa PSII photochemistry and carotenoid content were unaffected by salinity, but a reduction in chlorophyll content was observed at 800 mM NaCl. Similar results were found in A. halimus, but with a decrease in the efficiency of PSII (F'v/F'm) occurred at 800 mM. Conversely, in M. arborea plants we observed a significant reduction in pigment concentrations and chlorophyll fluorescence parameters. The marked toxic effect of Na⁺ and/or Cl⁻ observed in M. arborea indicates that salt damage effect could be attributed to ions’ toxicity, and that the reduction in photosynthesis is most probably due to damages in the photosynthetic apparatus rather than factors affecting stomatal closure. For the two halophyte species, it appears that there is occurrence of co-limitation of photosynthesis by stomatal and non-stomatal factors. Our results suggest that both N. retusa and A. halimus show high tolerance to both high salinity and photoinhibition while M. arborea was considered as a slightly salt tolerant species.

Ograniczanie wyników

3 Acta Physiologiae Plantarum

3 Boughalleb F.

2 Denden M.

2 Tiba B. B.

1 Hajlaoui H.

1 2011

2 2009

Physiological and anatomical changes induced by drought in two olive cultivars (cv Zalmati and Chemlali)

Anatomical changes induced by increasing NaCl Salinity in three fodder shrubs, Nitraria retusa, Atriplex halimus and Medicago arborea

Photosystem II photochemistry and physiological parameters of tree fodder shrubs, Nitraria retusa, Atriplex halimus and Medicago arborea under salt stress