The production of reserve starch granules in the amyloplasts of Pellionia daveauana N. E. Br.

Salema, R.; Badenhuizen, N. P.

doi:10.1016/s0022-5320(67)80107-2

Cited by 32 publications

(16 citation statements)

References 16 publications

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“…These plastids also contained prolamellar and other electron-dense bodies. The presence of prolamellar bodies indicates that these amyloplasts are actually virescent chloroamyloplasts (15). This is not surprising, because we have observed that alfalfa roots can turn green when exposed to light.…”

Section: Resultsmentioning

confidence: 56%

Starch Grain Distribution in Taproots of Defoliated Medicago sativa L.

Habben¹,

Volenec²

1990

Plant Physiol.

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Defoliation of alfalfa (Medicago sativa L.) results in a cyclic pattern of starch degradation followed by reaccumulation in taproots. Characterization of changes in anatomical distribution of starch grains in taproots will aid our understanding of biochemical and physiological mechanisms involved in starch metabolism in taproots of this species. Our objectives were to determine the influence of defoliation on starch grain distribution and size variation in taproots of two alfalfa lines selected for contrasting concentrations of taproot starch. In addition, we used electron microscopy to examine the cellular environment of starch grains, and computer-based image optical analysis to determine how cross-sectional area of tissues influenced starch accumulation. Taproots of field-grown plants were sampled at defoliation and weekly thereafter over a 28-day period. Taproot segments were fixed in glutaraldehyde and prepared for either light or electron microscopy. Transverse sections were examined for number and size of starch grains and tissue areas were measured. Starch grains were located throughout bark tissues, but were confined primarily to ray parenchyma cells in wood tissues. During the first week of foliar regrowth after defoliation, starch grains in ray cells near the cambium disappeared first, while degradation of those near the center of the taproot was delayed. During the third and fourth weeks of regrowth, there was a uniform increase in number of starch grains per cell profile across the rays, but by 28 days after defoliation there were more starch grains in ray cells near the cambium than in cells near the center of the taproot (low starch line only). Bark tissues from both lines showed synchronous degradation and synthesis of starch grains that was not influenced greatly by cell location. Diameter of starch grains varied with cell location in medullary rays during rapid starch degradation, but was not influenced by cell position in bark tissues. Therefore, during foliar regrowth there is a spatial separation in starch degradation and synthesis in alfalfa taproots. Amyloplasts from alfalfa taproots contained numerous starch grains, prolamellar-, and electron-dense bodies. The high starch line had 23% more cross-sectional area as ray cells in wood tissues when compared to the low starch line, which may explain part of the difference in starch accumulation between these alfalfa lines.Taproots of alfalfa (Medicago sativa L.) accumulate high concentrations (>250 g kg-' dry weight) of starch. Degrada-

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Section: Resultsmentioning

confidence: 56%

Starch Grain Distribution in Taproots of Defoliated Medicago sativa L.

Habben¹,

Volenec²

1990

Plant Physiol.

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“…One clue comes from observations that granule initiation in maize, oat (Avena sativa), or barley (Hordeum vulgare) endosperm occurs in plastids containing internal thylakoids, possibly within pockets of such membranes (Buttrose, 1960;Badenhuizen, 1969). Based on such ultrastructural data, association with thylakoid-like membranes within amyloplasts has been proposed as a functional aspect of starch polymer synthesis, granule formation, and growth (Salema and Badenhuizen, 1967;Barlow and Sargent, 1978). Direct evidence addressing this hypothesis is lacking; however, this study provides some support by showing a drastic switch in granule complexity when membrane lipids are altered.…”

Section: Galactolipid Function In Amyloplastsmentioning

confidence: 61%

Maize opaque5 Encodes Monogalactosyldiacylglycerol Synthase and Specifically Affects Galactolipids Necessary for Amyloplast and Chloroplast Function

et al. 2011

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The maize (Zea mays) opaque5 (o5) locus was shown to encode the monogalactosyldiacylglycerol synthase MGD1. Null and point mutations of o5 that affect the vitreous nature of mature endosperm engendered an allelic series of lines with stepwise reductions in gene function. C 18:3 /C 18:2 galactolipid abundance in seedling leaves was reduced proportionally, without significant effects on total galactolipid content. This alteration in polar lipid composition disrupted the organization of thylakoid membranes into granal stacks. Total galactolipid abundance in endosperm was strongly reduced in o5 -mutants, causing developmental defects and changes in starch production such that the normal simple granules were replaced with compound granules separated by amyloplast membrane. Complete loss of MGD1 function in a null mutant caused kernel lethality owing to failure in both endosperm and embryo development. The data demonstrate that low-abundance galactolipids with five double bonds serve functions in plastid membranes that are not replaced by the predominant species with six double bonds. Furthermore, the data identify a function of amyloplast membranes in the development of starch granules. Finally, the specific changes in lipid composition suggest that MGD1 can distinguish the constituency of acyl groups on its diacylglycerol substrate based upon the degree of desaturation.

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“…A subsequent eccentric growth indicates that the synthesizing enzymes are pushed in one direction toward the distal end of the granule, while they are either absent or of reduced activity at the proximal part holding the hilum (French, 1984). Such unidirectional elongation has been well described and explained for the eccentric granules of Pellionia daveauana (Badenhuizen, 1969;Binz, 1892;Salema and Badenhuizen, 1967). In the development of P. daveauana starch, it was shown that when the granules reach a certain size, the bulk of the stromal enzymes is no longer surrounding the whole granule, but is located as a cap at the distal end.…”

Section: Discussionmentioning

confidence: 91%