Impacts of urban levels of ozone on Pinus halepensis foliage

Eugenia uniflora and Clusia hilariana seedlings were submitted to simulated acid rain, pH 3, for 40 days. The degree of visible injury and the anatomical and micromorphological alterations were determined 24 hours after the last simulation. E. uniflora presented a higher degree of leaf necrosis. The adaxial epidermis and part of the palisade parenchyma of the entire leaf blade were affected and hypertrophy, hyperplasia and cicatrization tissue differentiation occurred. Erosion and morphological modification of the epicuticular wax and alterations in the epidermis were detected on the upper and lower leaf surfaces. Stomata with deformed ostioles and rupture of the stomatal ledge were observed. C. hilariana presented necrosis in leaf margin and in abaxial leaf surface, showing collapsed cells or with plasmolized aspect, cicatrization tissue, epicuticular wax alterations, occasional leaf perforations, irregular arrangement of adaxial epidermis cells and twisted subsidiary cells. The structural alterations indicated a greater susceptibility of E. uniflora to acid rain. The lower sensibility of C. hilariana can be related with the anatomical characteristics as: thick cuticle with evident cuticular flanges, three layers of hypodermis and mesophyll more thick and compact.

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“…Soda et al (2000) also observed in Pinus halepensis collapsed mesophyll cells that accumulated starch and lipids in response to pollutants.…”

Section: Discussionmentioning

confidence: 70%

Micromorphological and anatomical alterations caused by simulated acid rain in Restinga plants: Eugenia uniflora and Clusia hilariana

Silva

Oliva

Azevedo

et al. 2005

Water Air Soil Pollut

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“…According to other studies, cell structural changes indicate that exposure to air pollutants, such as exhaust gases (Viskari et al 2000) or ozone (Holopainen et al 1996;Soda et al 2000), or nutrient deficiencies such as Mg deficiency (Hannick et al 1993), accelerate senescence of conifer needles. The meaning of the word senescence has often been used incorrectly to describe ageing in green conifer needles (e.g.…”

Section: Introductionmentioning

confidence: 95%

Microscopic structure of Scots pine (Pinus sylvestris (L.)) needles during ageing and autumnal senescence

Kivimäenpää

Sutinen

2007

Trees

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Needle ageing and senescence were studied in Scots pine (Pinus sylvestris) trees growing in natural conditions with minimal anthropogenic influence. The four existing needle generations were analyzed by light and transmission electron microscopy before and during autumnal yellowing of the oldest needle generation. The change from green to yellow occurred within less than 4 days in central Finland. The structure of the oldest needles remained largely intact as long as they were green. Increase in mitochondrion size and hypertrophy of the phloem parenchyma were the only changes, probably related to the approaching senescence. In the yellow needles, the structure of the mesophyll tissue varied from nearly intact with reduced chloroplasts and higher numbers of plastoglobuli, to totally disintegrated cells. In the disintegrated cells, peroxisomes were absent, and chloroplasts were smaller with a patchy appearance and degraded, eventually emptylooking stroma. Mitochondria were enlarged, but retained integrity until the last stages of deterioration, and lipids increased. At the light microscopic level, vacuolar volume in mesophyll cells and cavity formation in transfusion tissue increased. Ageing was characterized by increases in the vacuolar volume and cytoplasmic lipids, altered appearance of vacuolar tannin from homogenous 'sandy', to large spherical drops and finally to a large mass in the mesophyll, and by hypertrophy and tannin accumulation in the phloem parenchyma. Changes related to needle ageing, senescence and cell location in the mesophyll tissue were discussed relative to findings with stress by strong light, weather conditions and ozone.

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“…Suberization and/or lignification of radial and transverse walls of the bundle sheath, including typical Casparian strips, have indeed been detected in needles of numerous Pinaceae species by microscopic staining techniques, electron microscopy and spectroscopic analysis (Fig. 2a, Carde 1978; Canny 1993; Kaku 1971; Scholz and Bauch 1973; Soda et al 2000; Wu et al 2001; Wu et al 2003). Casparian strips have not been reported outside the Pinaceae, but representatives of other gymnosperm families have often wall modifications in the bundle sheath cells.…”

Section: Leaf Morphology and Anatomymentioning

confidence: 96%

Symplasmic transport and phloem loading in gymnosperm leaves

2010

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Despite more than 130 years of research, phloem loading is far from being understood in gymnosperms. In part this is due to the special architecture of their leaves. They differ from angiosperm leaves among others by having a transfusion tissue between bundle sheath and the axial vascular elements. This article reviews the somewhat inaccessible and/or neglected literature and identifies the key points for pre-phloem transport and loading of photoassimilates. The pre-phloem pathway of assimilates is structurally characterized by a high number of plasmodesmata between all cell types starting in the mesophyll and continuing via bundle sheath, transfusion parenchyma, Strasburger cells up to the sieve elements. Occurrence of median cavities and branching indicates that primary plasmodesmata get secondarily modified and multiplied during expansion growth. Only functional tests can elucidate whether this symplasmic pathway is indeed continuous for assimilates, and if phloem loading in gymnosperms is comparable with the symplasmic loading mode in many angiosperm trees. In contrast to angiosperms, the bundle sheath has properties of an endodermis and is equipped with Casparian strips or other wall modifications that form a domain border for any apoplasmic transport. It constitutes a key point of control for nutrient transport, where the opposing flow of mineral nutrients and photoassimilates has to be accommodated in each single cell, bringing to mind the principle of a revolving door. The review lists a number of experiments needed to elucidate the mode of phloem loading in gymnosperms.

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Impacts of urban levels of ozone on Pinus halepensis foliage

Cited by 38 publications

References 70 publications

Micromorphological and anatomical alterations caused by simulated acid rain in Restinga plants: Eugenia uniflora and Clusia hilariana

Micromorphological and anatomical alterations caused by simulated acid rain in Restinga plants: Eugenia uniflora and Clusia hilariana

Microscopic structure of Scots pine (Pinus sylvestris (L.)) needles during ageing and autumnal senescence

Symplasmic transport and phloem loading in gymnosperm leaves

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