Senescent plant

This chapter brings together information concerning structural features, spectral characteristics, distributions, and functions of major chlorophylls in photosynthetic organisms. Other topics discussed include biosynthesis and degradation in senescent plants and ripening fruits and potential biological properties of chlorophylls. 

Heaton, J.W. and Marangoni, A.G., Chlorophyll degradation in processed foods and senescent plant tissues. Trends Food Sci. TechnoL, 1, 8, 1996. 

When Winter senescent plant material was harvested and extracted, yields of OFAs were greatly reduced. OFAs from the four ponds were extracted easily from 20-50 liters of pond water by passing the water through a tube filled with ODS silica. These ponds produced between 1 and 1.5 ppm of OFAs after elution with methyl formate. The origin of I, Ila and lib in these ponds is uncertain at this time. 

Saprophytic, dark pigmented fungi such as Alternaria spp. can infect a wide range of plant species, especially tissues that are exposed to other biotic or abiotic stressors and older and senescing plant tissues. Also, wet weather conditions favour attack by Alternaria spp. Inoculum of Alternaria and potentially production of altemariol is further enhanced when cereal straw and stubble is left on the soil surface and not sufficiently incorporated into the soil after harvest (direct seeding and minimum tillage systems). 

Usuda H (1995) Phosphate deficiency in maize. V. Mobilization of nitrogen and phosphorus within shoots of young plants and its relationship to senescence. Plant Cell Physiol 36 1041-1049. doi http //pcp.oxfordjournals.org/cgi/content/abstract/36/6/1041 van der Heijden MGA, Boiler T, Wiemken A, Sanders IR (1998a) Different arbuscular mycor-rhizal fungal species are potential determinants of plant community structure. Ecology 79 2082-2091... 

With the authentic red tetrapyrrolic RCC (11) available as a reference material from the synthetic work (76), an identical red compound was detected in senescent plant material and was identified as an elusive red chlorophyll catabolite, when Pheo a (5a) was incubated with aerated extracts of washed membranes of senescent Canola chloroplasts (see Scheme 8) (68, 69). In addition, incubation of chemically pre-... 

Barr, R. and C.B. Arntzen Occurrence of 5-tocopherylquinone in higher plants and its relation to senescence Plant Physiol. 44 (1969) 593-598. 

Physical leaching of soluble organic phosphorus from senescing plant tissue... 

Osborne, T. Z., R W. Inglett, and K. R. Reddy. 2007. The use of senescent plant biomass to investigate relationships between potential particulate and dissolved organic matter in a wetland ecosystem. Aquat. Bot. 86 53-61. 

Keller R, Springer F, Renz A, Kossmann J. Antisense inhibition of the GDP-mannose pyrophosphorylase reduces the ascorbate content in transgenic plants leading to developmental changes during senescence. Plant J 1999 19 131-141. 

Hong MC, Chang MC (1998) Purification and characterization of an alkaline lipase from a newly isolated Acinetobacter mdioresistem CMC-1. Biotechnol Lett 20 1027-1029 Hong Y, Wang TW, Hudak KA et al. (2000) An ethylene-induced cDNA encoding a lipase expressed at the onset of senescence. Plant Biol 97 8717-8722 Houde A, Kademi A, Leblanc D (2004) Lipases and their industrial applications an overview. Appl Biochem Biotechnol 118(1-3) 155-170... 

Ethylene is unique in that it is found only in the gaseous form. It induces ripening, causes leaves to droop (epinasty) and drop (abscission), and promotes senescence. Plants often increase ethylene production in response to stress, and ethylene often is found in high concentrations within cells at the end of a plant s life. The increased ethylene in leaf tissue in the fall is part of the reason leaves fall off trees. Ethylene also is used to ripen fruits (e.g., green bananas). 

In senescent plant tissues, e.g., leaves, large amounts of chlorophyll are degraded to compounds of primary metabolism. 

Presumably the most studied essential oil plant is peppermint (M. piperita L.). Already in the 1950s Lemli (1955) stated that the proportion of menthol to menthone in peppermint leaves changes in the course of the development toward higher menthol contents. Lawrence (2007) has just recently shown that from immature plants via mature to senescent plants the content of menthol increases... 

Presumably the most studied essential oil plant is peppermint (Mentha x piperita L.). Already in the 1950s Lemli (1955) stated that the proportion of menthol to menthone in peppermint leaves changes in the course of the development toward higher menthol contents. Lawrence (2007) has just recently shown that from immature plants via mature to senescent plants the content of menthol increases (34.8-39.9 8.2%) and correspondingly the menthone content decreases dramatically (26.8-17.4-4.7%). At the same time, also an increase of menthyl acetate from 8.5% to 23.3% of the oil could be observed. At full flowering, the peppermint herb oil contains only 36.8% menthol but 21.8% menthone, 7.7% menthofuran, and almost 3% pulegone due to the fact that the flower oils are richer in... 

Mayak S, Halevy AH (1972) Interrelationships of ethylene and abscisic acid in the control of rose petal senescence. Plant Physiol 50 341-346 McBride R, Evans ML (1977) Auxin inhibition of acid- and fusicoccin-induced elongation in lentil roots. Planta 136 97-102... 

Keskitalo, J., Bergquist, G., Gardestrom, P. Jansson, S. (2005). A cellular timetable of autumn senescence. Plant Physiology, 139,1635-1648. 

In green coconut water, between pH 5.5 and 6.0, and at 25°C and 35°C, optimum activities of polyphenoloxydase (PPO) and peroxidase (POD) are observed. PPO is an enzyme that is found in chloroplasts, plastids and is also present in the cytoplasm of the ripened senescing plants. It helps the plant to resist microbial infections and extreme climatic conditions. The ratio of these enzymes (PPO/POD) in coconut water ranges from 0.2 to 16.7 and varies even within similar coconut varieties. This ratio depends on the stage of maturity at harvest, the variety and storage condition of the fruit, the cultivation conditions and on the mode of extraction of the coconut water. 

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