Ozone-Induced Alterations in Quantity and Activity of Rubisco: Implications for Foliar Senescence

The effects of simulated acidic fog and inoculation with Septoria betulae Pass. on foliar symptom development and foliar senescence of Betula papyrifera Marsh. and Betula cordifolia Regel seedlings were investigated in 1997 and 1998 under greenhouse conditions. An interactive role may exist between acidic fog events and S. betulae in causing birch foliar browning, a disease reported over the past decade to occur on mature trees growing adjacent to the Bay of Fundy, Canada. Seedlings received applications of simulated fog adjusted to pH 3.2, 4.2, and 5.6 or a no-fog treatment. Inoculation treatments at each fog pH level were accomplished through spray atomization with S. betulae conidial suspensions and by placing naturally infected birch leaves bearing pycnidia of the fungus on plastic nets suspended above seedlings in enclosed chambers. Percent symptomatic leaf area of seedlings inoculated with S. betulae was nearly double that recorded for non-inoculated seedlings. Foliar browning resembled symptoms observed on mature trees in the field. Foliar symptoms were observed on non-inoculated seedlings, with greater severities associated with seedlings exposed to the most acidic fog treatment. Leaf senescence was also greatest for spray-inoculated leaves that had been exposed to the pH 3.2 fog treatment. Pycnidial development was not influenced by the pH of the fog treatments but was greater in all fog treatments than in no-fog treatments. Although both acidic fog and S. betulae infection are able to cause symptoms independently, the data suggest that an interactive role may exist in causing birch foliar browning. However, to obtain the same severity of foliar browning as observed on natural forest-grown trees in the Bay of Fundy region, S. betulae must be present.

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Effect of Autumn Foliar Senescence on Chlorophyll a:b Ratio and Respiratory Enzymes of Populus tremuloides

Bulletin of the Torrey Botanical Club ◽

10.2307/2996991 ◽

1993 ◽

Vol 120 (3) ◽

pp. 269 ◽

Cited By ~ 10

Author(s):

Maria A. Dean ◽

Charles A. Letner ◽

James H. Eley

Keyword(s):

Populus Tremuloides ◽

Respiratory Enzymes ◽

Foliar Senescence

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Controlled atmospheres and sugar can delay malate synthase gene expression during asparagus senescence

Functional Plant Biology ◽

10.1071/pp01237 ◽

2002 ◽

Vol 29 (9) ◽

pp. 1045 ◽

Cited By ~ 5

Author(s):

Simon A. Coupe ◽

Ben K. Sinclair ◽

Sheryl D. Somerfield ◽

Paul L. Hurst

Keyword(s):

Gene Expression ◽

Single Gene ◽

Malate Synthase ◽

Open Reading Frame ◽

Asparagus Officinalis ◽

High Identity ◽

Reading Frame ◽

Controlled Atmospheres ◽

Foliar Senescence

A cDNA clone encoding malate synthase (MS; EC 4.1.3.2) was isolated from a 48-h postharvest asparagus (Asparagus officinalis L.) spear cDNA library using a MS clone from Brassica napus. The asparagus MS (AoMS1) cDNA hybridized to a 1.9-kb transcript that increased in abundance preferentially in spear-tip tissue during postharvest storage. The AoMS1 transcript also accumulated during natural foliar senescence of asparagus fern. The cDNA consists of 1960 nucleotides with an open reading frame of 1665 nucleotides or 555 amino acids, and encodes a deduced protein with a predicted Mr of 63 kDa and a pI of 8.1. The deduced amino acid sequence of AoMS1 showed high identity with the B. napus MS clone (77.2%) used to isolate it, and with MS from cucumber (77%). Genomic Southern analysis suggests that a single gene in asparagus encodes AoMS1. Controlled- atmosphere treatments aimed at reducing deterioration of harvested asparagus spears reduced the expression of AoMS1. The reduction was correlated with the reduced oxygen level, and reduced MS enzyme activity was also observed. Asparagus cell cultures were used to test the role of sugar status in regulating AoMS1 gene expression. In cultures without sucrose there was an accumulation of AoMS1 transcript that was absent in cultures containing sucrose.

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The Impact of Root Temperature on Photosynthesis and Isoprene Emission in Three Different Plant Species

The Scientific World JOURNAL ◽

10.1100/2012/525827 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 14

Author(s):

Mauro Medori ◽

Lucia Michelini ◽

Isabel Nogues ◽

Francesco Loreto ◽

Carlo Calfapietra

Keyword(s):

Plant Species ◽

High Stress ◽

Root Temperature ◽

Isoprene Emission ◽

Perennial Plant ◽

Good Marker ◽

Volatile Organic ◽

Foliar Senescence ◽

Populus X Euramericana ◽

The Impact

Most of the perennial plant species, particularly trees, emit volatile organic compounds (BVOCs) such as isoprene and monoterpenes, which in several cases have been demonstrated to protect against thermal shock and more generally against oxidative stress. In this paper, we show the response of three strong isoprene emitter species, namely,Phragmites australis, Populus x euramericana, andSalix phylicifoliaexposed to artificial or natural warming of the root system in different conditions. This aspect has not been investigated so far while it is well known that warming the air around a plant stimulates considerably isoprene emission, as also shown in this paper. In the green house experiments where the warming corresponded with high stress conditions, as confirmed by higher activities of the main antioxidant enzymes, we found that isoprene uncoupled from photosynthesis at a certain stage of the warming treatment and that even when photosynthesis approached to zero isoprene emission was still ongoing. In the field experiment, in a typical cold-limited environment, warming did not affect isoprene emission whereas it increased significantly CO2assimilation. Our findings suggest that the increase of isoprene could be a good marker of heat stress, whereas the decrease of isoprene a good marker of accelerated foliar senescence, two hypotheses that should be better investigated in the future.

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