Effects of position and age on leaf photosynthesis in corn (Zea mays)

The effects of ear removal on gas exchange traits, chlorophyll, and leaf N profiles, and activities of ribulose 1,5-bisphosphate carboxylase/ oxygenase and phosphoenolpyruvate carboxylase were examined using four maize hybrids (B73 x Mol7, B73 x LH38, FS854, and CB59G x LH38) and four inbred lines (B73, Mol7, LH38, and CB59G) The objectives of this study were (a) to determine effect of ear removal on CO2 exchange and associated carboxylase activities, and internal CO2 concentrations in order to determine the relative importance of metabolic versus stomatal effects in the ear removal response; and (b) to determine how ear removal affects inbred parents of hybrids which differ markedly in response to ear removal.

supporting

confidence: 79%

Effect of Ear Removal on CO₂ Exchange and Activities of Ribulose Bisphosphate Carboxylase/Oxygenase and Phosphoenolpyruvate Carboxylase of Maize Hybrids and Inbred Lines

Crafts‐Brandner¹,

Poneleit²

1987

“…Because the accumulation of photosynthate in the leaf may impair leaf functions, Allison and Weinmann (1) implied that the accumulation of carbohydrates in the leaves was related to the rapid development of senescence. Subsequently, Christensen et al (4) and Thiagarajah et al (20) using different maize cultivars, reconfirmed that bagging or removal ofears accelerated rather than delayed senescence. Using the maize hybrid, B73 x Mol 7, Christensen et al (4) confirmed that ear removal resulted in a marked decrease in photosynthetic activity (measured by dry weight accumulation of all above-ground parts).…”

mentioning

confidence: 97%

Differential Senescence of Maize Hybrids following Ear Removal

Crafts‐Brandner¹,

Below²,

Harper³

et al. 1984

Visual senescence symptoms and associated changes in constituent contents of three field-grown maize (Zea mays L.) hybrids (Pioneer brand 3382, B73 x Mol7, and Farm Service brand 854) were compared in response to ear removal. Whole plants were harvested at eight intervals during the grain-filling period, and analyzed for dry matter, total N and nitrate N, phosphorus, sugars, and starch.Upper leaves of earless P3382 and B73 x Mol7 showed reddish discoloration by 25 days after anthesis (DAA) and all leaves had lost most of their chlorophyll by 40 DAA. In striking contrast, leaves of earless FS854 plants remained green and similar in appearance to eared controls throughout the grain-filling period.For all hybrids, ear removal led to a decrease in dry weight, reduced N, total N, and phosphorus contents of the total plant, and an increase in carbohydrate content of the leaves and stalks, relative to respective controls. Although changes in carbohydrate and N contents, which previously had been associated with senescence, were observed for all earless hybrids, these changes were followed by accelerated senescence and early death only for P3382 and B73 x Mol7. By 30 DAA, earless P3382 and B73 x Mol7 plants ceased to accumulate dry weight, total N, and phosphorus, indicating a termination of major metabolic activities. In contrast, earless FS854 plants retained a portion of these metabolic activities until 58 DAA, indicating a role for roots in determining rate of

“…Apparently the presence of pods only altered the partitioning of plant constituents (7). Based on the seasonal profiles ofChl, and activities ofthe functional enzymes nitrate reductase, nitrogenase and RuBPCase, the initiation of leaf senescence was similar for podded and depodded plants (7,8).Although Moss (17) reported that the prevention ofpollination (ear bagging or removal) delayed senescence in maize, other workers (1,3,25) found such treatments accelerated leaf and plant senescence. Subsequent work (5, 6, 27) resolved this conflict by showing the response was a reflection of genotype.…”

mentioning

confidence: 99%

“…Although Moss (17) reported that the prevention ofpollination (ear bagging or removal) delayed senescence in maize, other workers (1,3,25) found such treatments accelerated leaf and plant senescence. Subsequent work (5,6,27) resolved this conflict by showing the response was a reflection of genotype.…”

mentioning

confidence: 99%

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Effect of Head Removal on Leaf Senescence of Sunflower

Ho¹,

Below²,

Hageman³

1987

Greenhouse and field studies examined the effect of flower or seedhead removal on leaf senescence and associated changes in sunflower (Helianthus annuus L.) plants. At intervals during seed development, selected leaves (leaves 6 through 8 from the top in the greenhouse and leaf 7 from the top in the field) were harvested and analyzed for chlorophyll, specific leaf weight, N, P, soluble protein, and electrophoretic gel profiles of soluble polypeptides. In both the greenhouse and the field, the leaves of headless plants retained or accumulated more N, P, soluble protein, and dry weight than leaves of plants with heads. Obviously, head removal affected the partitioning of these metabolites during seed development. None of the treatments resulted in the formation of new polypeptides (electrophoretic gel profiles). Comparisons of the rates and extent of loss ofchlorophyll, soluble protein, and polypeptide bands (especially ribulose 1,5-bisphosphate carboxylase) from the leaves of headed and deheaded plants showed that head removal delayed the rate of development of leaf senescence for the greenhouse-grown but had much less effect on fieldgrown plants. These findings illustrate the variability in different parameters commonly associated with the leaf senescence processes of headed and deheaded sunflower plants grown under different environments.Senescence has been described as the natural deteriorative process leading to death of an organ or organism (12). This process is complex, controversial, and not well understood, especially with respect to the causal factor(s) (26). Additional information concerning the cause, course, and control of senescence is of agronomic importance because of the high positive correlation between leaf area duration and grain yield (9).There are no comprehensive theories of senescence (13) depodding resulted in de novo synthesis of four polypeptides (30), he concluded that depodding altered leaf function (became a sink) rather than delaying or preventing senescence. CraftsBrandner et al. (7,8) reported similar results from depodding soybean plants (cv Harosoy), except that RuBPCase was only initially lower in the leaves of depodded plants. By maturity, the depodded plants had accumulated as much dry weight (net photosynthesis) and N in the above ground parts as the podded plants. Apparently the presence of pods only altered the partitioning of plant constituents (7). Based on the seasonal profiles ofChl, and activities ofthe functional enzymes nitrate reductase, nitrogenase and RuBPCase, the initiation of leaf senescence was similar for podded and depodded plants (7,8).Although Moss (17) reported that the prevention ofpollination (ear bagging or removal) delayed senescence in maize, other workers (1,3,25) found such treatments accelerated leaf and plant senescence. Subsequent work (5, 6, 27) resolved this conflict by showing the response was a reflection of genotype. A detailed comparison of such divergent genotypes (5, 6) permitted the conclusion that the ear per se does not fully...