Apple Leaf Senescence: Leaf Disc Compared to Attached Leaf

Self Cite

Section: Resultsmentioning

confidence: 96%

“…The trees were younger than those used in previous studies (19,20). Leaf discs (diameter 1.5 cm) were punched from the leaf blade avoiding the midrib and main veins and were used in all subsequent analyses and treatments.…”

Section: Methodsmentioning

confidence: 99%

Incorporation of ¹⁴C-Leucine into Apple Leaf Protein and Its Inhibition by Protein Synthesis Inhibitors during Growth and Senescence

Spencer

1973

Self Cite

“…The earliest researches tended to concentrate on the nucleic acids (1 1, 24, 43, 44), then proteolysis came to the fore, together with the balance between proteolysis and protein synthesis, and the specific roles of individual amino acids (29 and see 35). Comparison between the behavior of isolated leaves and those attached to the plant then brought out the important part played by transport phenomena (22,32,38). The continuation of studies of the difference between senescence in darkness and in light has recently introduced an apparently controlling function for stomatal aperture (21,36,37), a finding which helps to explain the apparently time-limited and localized effect oflight in delaying senescence (39).…”

mentioning

confidence: 97%

“…The earliest researches tended to concentrate on the nucleic acids (1 1, 24, 43, 44), then proteolysis came to the fore, together with the balance between proteolysis and protein synthesis, and the specific roles of individual amino acids (29 and see 35). Comparison between the behavior of isolated leaves and those attached to the plant then brought out the important part played by transport phenomena (22,32,38 (e.g. 18), it was natural to look for a function of this hormone in senescence, and indeed it was reported early to increase leaf senescence (6,12, 27).…”

Section: Introductionmentioning

confidence: 99%

The Role of Ethylene in the Senescence of Oat Leaves

Gepstein¹,

Thimann²

1981

141

The evolution of ethylene, both from the endogenous source and from added 1-aminocyclopropane-1-carboxylic acid (ACC), has been foUlowed in close relationship with the senescent loss of chlorophyll from seedling oat leaves. In white light, where chlorophyll loss is slow, the ethylene evolution increases slowly at first, but when the loss of chlorophyll becomes more rapid, ethylene evolution accelerates. CoCI2 inhibits this increase and correspondingly maintains the chlorophyll content, with an optimum concentration of 10 micromolar. The rapid rate of chlorophyll loss in the dark is slightly decreased by 3-aminoethoxyvinyl glycine (AVG), by cobalt, and slightly stimulated by ACC. The slower chlorophyll loss in white light, however, is almost completely inhibited by silver ions, greatly decreased by cobalt and by AVG, and strongly increased by ACC. Since the chlorophyll loss is accompanied by proteolysis, it represents true senescence. Chlorophyll loss in light is also strongly antagonized by C02, 1% CO2 giving almost 50% chlorophyll maintenance in controls, while in the presence of added ACC or ethylene gas, the chlorophyll loss is 50% reversed by about 3% CO2. The ethylene system in leaves is thus more sensitive to CO2 than that in fruits. Indoleacetic acid also clearly decreases the effect of ACC. It is shown that kinetin, C02, Ag+, and indoleacetic acid, all of which oppose the effect of ethylene, nevertheless increase the evolution of ethylene by the leaves, and it is suggested that ethylene evolution may, in many instances, mean that its hormonal metabolism is being prevented.Abscisic acid somewhat increases ethylene evolution also, but its action in promoting senescence in light is antagonized only partially by Ag+, C02+, or AVG. For this and a number of other reasons it is concluded that ethylene and abscisic acid both independently control leaf senescence in the light.The study of leaf senescence continually brings to light more and more interactions. The earliest researches tended to concentrate on the nucleic acids (1 1, 24, 43, 44), then proteolysis came to the fore, together with the balance between proteolysis and protein synthesis, and the specific roles of individual amino acids (29 and see 35). Comparison between the behavior of isolated leaves and those attached to the plant then brought out the important part played by transport phenomena (22,32,38 (e.g. 18), it was natural to look for a function of this hormone in senescence, and indeed it was reported early to increase leaf senescence (6,12, 27). Our own experiments (14) '

“…Differences in the senescence pattern of attached leaves compared to detached leaves or leaf discs have been reported (13,14,24, 25).…”

Section: Introductionmentioning

confidence: 99%

Pyrophosphatase, Peroxidase and Polyphenoloxidase Activities during Leaf Development and Senescence

Patra¹,

Mishra²

1979

Inorganic pyrophosphatase, peroxidase, and polyphenoloxidase activities were studied as the function of leaf insertion level in eight monocotyledonous and eight dicotyledonous species. Alkaline inorganic pyrophosphatase shows a declining activity toward the end of senescence whereas no regular drift in either peroxidase or polyphenoloxidase activities was noticed during senescence of attached leaves. In the primary leaves of rice, peroxidase and polyphenoloxidase activities were high in the senescent leaves and there exists a correlation between chlorophyll content and peroxidase activity though not with polyphenoloxidase activity. Upon detachment leaves exhibit increasing peroxidase and polyphenoloxidase activities with time. The distribution of the enzyme activities during senescence of attached leaves is suggested to be species-specific, and an increase in peroxidase and polyphenoloxidase activities cannot be taken as an indicator of leaf senescence.A number of reports are available regarding the increase (1, 2, 4, 7-10, 14, 16, 19) and/or decrease (4,10,12,19,20) in activities of several hydrolyzing and oxidative enzymes during senescence of leaves. Differences in the senescence pattern of attached leaves compared to detached leaves or leaf discs have been reported (13,14,24, 25).Both acid and alkaline inorganic pyrophosphatase (EC 3.6.1.1) occur in higher plants (17). It has been suggested that the alkaline inorganic pyrophosphatase, having extremely high affinity for pyrophosphate, is associated with the anabolic process in the leaf, while acid inorganic pyrophosphatase participates in the catabolic process (7,21,23 This investigation was undertaken to study the distribution pattern of inorganic pyrophosphatase, peroxidase, and polyphenoloxidase activities in attached leaves of different physiological ages and to determine if the changes in peroxidase and polyphenoloxidase activities during leaf senescence can be considered to be species-specific. MATERIALS AND METHODSThe following species were investigated: monocotyledons: Amomum aromaticum Roxb., Eleusine corocana Gaertn., Hordeum vulgare L., Oryza sativa L., Pennisetum typhoideum Rich., Sorghum vulgare Pers., Triticum vulgare Villars., and Zea mays L.; dicotyledons: Arachis hypogaea L., Boerhaavia diffusa L., Chenopodium album L., Crotolaria striata DC., Hibiscus micranthus L., Nicotiana plumbaginifolia Viv., Raphanus sativus L., and Tabernaemontana coronaria Br.Healthy plant samples were collected on sunny days at 10 AM and the approximate age of the organs determined by the method of Kornilov et al. (11). The samples were transported to the laboratory in polyethylene bags covered with crushed ice. The leaves were numbered from the apex downward so as to obtain subsamples representative of various developmental stages. The leaves were excised within 15 min of collection, washed thoroughly with tap water, and then in distilled H20. The leaves were blotted, weighed, and stored in a refrigerator at 8 C for 30 min.Enzyme Extraction and Assay. Enz...