Morphological Observations on the Early Imbibition of Water by Sida spinosa (Malvaceae) Seed

Gh, Egley; RNJr, Paul

doi:10.2307/2442715

Cited by 31 publications

(39 citation statements)

References 13 publications

(26 reference statements)

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“…of the families with PY, except the Leguminosae, occurs only after a plug or lid that closes the discontinuity ('water-gap') in the waterimpermeable layer(s) in the chalazal region is dislodged or disrupted, thereby creating a pore for entrance of water to the embryo. In Malvaceae, the so-called chalazal plug separates from the underlying subpalisade layer (Egley & Paul 1981;Egley et al 1986;Egley 1989), and in Cannaceae the imbibition lid separates from the rupture layer (Grootjen & Bouman 1988). The subpalisade layer and the rupture layer occur only below the chalazal plug and imbibition lid, respectively, in seeds in these two families.…”

Section: Cochlospermaceaementioning

confidence: 99%

Taxonomy, anatomy and evolution of physical dormancy in seeds

Baskin

2000

Plant Species Biology

483

444

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Physical dormancy (PY) is caused by a water-impermeable seed or fruit coat. It is known, or highly suspected, to occur in nine orders and 15 families of angiosperms (sensu Angiosperm Phylogeny Group 1998), 13 of which are core eudicots. The Zingiberales is the only monocot order, and Cannaceae (Canna) the only monocot family, in which PY is known to occur. Six of the nine orders, and 12 of the 15 families, in which PY occurs are rosids. Furthermore, six of the families belong to the Malvales. The water-impermeable palisade layer(s) of cells are located in the seed coats of 13 of the families, and in the fruit coats of Anacardiaceae and Nelumbonaceae. In all 15 families, a specialized structure is associated with the water-impermeable layer(s). The breaking of PY involves disruption or dislodgment of these structures, which act as environmental 'signal detectors' for germination. Representatives of the nine angiosperm orders in which PY occurs had evolved by the late Cretaceous or early Tertiary (Paleogene). Anatomical evidence for PY in fruits of the extinct species Rhus rooseae (Anacardiaceae, middle Eocene) suggests that PY had evolved by 43 Ma, and probably much earlier. We have constructed a conceptual model for the evolution of PY, and of PY+ physiological dormancy (PD), within Anacardiaceae. The model begins in pre-Eocene times with an ancestral species that has large, pachychalazal, non-dormant (ND), recalcitrant seeds. By the middle Eocene, a derived species with relatively small, partial pachychalazal, orthodox seeds and a water-impermeable endocarp (thus PY) had evolved, and by the Oligocene, PD had been added to the seed (true seed + endocarp) dormancy mechanism. It is suggested that climatic drying (Eocene), followed by climatic cooling (Eocene-Oligocene transition), were the primary selective agents in the development of PY. An evolutionary connection between PY and recalcitrance is suggested by the relatively high concentration of these two character states in the rosids. Phylogenetic data and fossil evidence seem to support the PY AE (PY + PD) evolutionary sequence in Anacardiaceae, which also may have occured in Leguminosae.

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Section: Cochlospermaceaementioning

confidence: 99%

Taxonomy, anatomy and evolution of physical dormancy in seeds

Baskin

2000

Plant Species Biology

483

444

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“…In Malvaceae the raphal tissue releases from the seed and exposes the chalazal area with a median cleft. Only raising of a blister, containing a region of the palisade layer, induces imbibition and germination (EGLEY & PAUL 1981). The seed dormancy in legume seeds is usually considered to be effected through the physical restriction of water uptake by the impermeable outer part of the epidermal layer of the Malpighian cells (WERKER 1980/1981, TRAN & CAVANAGH 1984, GOPINATHAN ~5 BABU 1985, SERRATO-VALENTI & al.…”

Section: Discussionmentioning

confidence: 99%

Functional aspects of mature seed coat of theCannaceae

et al. 1997

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Cannaceae seeds have been analysed regarding seed coat structure, germination and macromolecular composition of the seed coats. Data of several mass spectrometric techniques were combined with those of microscopic and histochemical techniques to acquire insight into the functions of the seed coat. Cannaceae seeds have an exotestal layer of Malpighian cells with a hydrophobic and a hydrophilic part. The hydrophobic part is mainly responsible for the impermeability of the seed and contains silica, callose, lignin as water repellent substances. Water can only enter the seed after a certain temperature-induced opening of an imbibition lid. During imbibition the hydrophilic part of the Malpighian cells swells and the seed coat ruptures due to differences in pressure in the upper and lower part of the Malpighian cells.Within the order Zingiberales there are still unsolved questions about the relations between seed coat structure, macromolecular composition and germination. Because there is a dearth of reliable data on the macromolecular components, the functional interpretation of seed coat has remained an almost unexplored field of research. The family Cannaceae has a somewhat distinct position within this order, having seeds with an exotesta of Malpighian cells, a long life time, and germination with an imbibition lid. Most taxa of the Zingiberales have an endotestal seed coat and germination with a seed lid.

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“…The chalazal area of prickly sida seeds was earlier confirmed as the site of initial water entry into the imbibing seed (Egley and Paul, 1981). It was also reported that a kidney-shaped portion of the seed coat near the chalazal slit formed a blister just prior to onset of imbibition in nonhard seeds.…”

mentioning

confidence: 83%

“…SEED COAT IMPERMEABILITY to water is an important factor in the dormancy and longevity of many weed seeds in the soil (Lewis, 1973;Stoller and Wax, 1974;Rolston 1978;Egley and Chandler, 1978). These seeds, often described as "hard," may survive for several years during which time the coats of some become permeable resulting in imbibition of water and germination.…”

mentioning

confidence: 99%

“…Prickly sida (Sida spinosa L.) is a weedy pest in the southern United States. The seed coats become impermeable to water during the latter stages of development as the seeds dehydrate to about 10% water content at maturity (Egley, 1976). Afterripening during warm dry storage or seed coat treatments such as scarification enable the seeds to imbibe water and germinate.…”

mentioning

confidence: 99%

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Development, Structure and Function of Subpalisade Cells in Water Impermeable Sida Spinosa Seeds

Egley

Paul²

1982

American J of Botany

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Newly matured prickly sida (Sida spinosa) seeds were hard, but afterripening, heat or pressure permitted water entry solely via a predefined region of the chalazal area. In this region, the raising of a “blister” formed by separation of the palisade of the seed coat from underlying tissues preceeded measurable water uptake by prickly sida seeds. A single subpalisade layer, unique to the region beneath the blister, was involved in the sequence of events in seed water uptake. The lateral walls of subpalisade cells invariably broke near the palisade border and cell contents were extruded onto the surface. This report describes the cytological development of the subpalisade layer from 1‐21 days post anthesis. Cells beneath the potential “blister” near the chalazal slit developed into columnar subpalisades and cells beneath the subpalisades or beyond the margins of the potential blister, developed into oval, thick‐walled chalazal cap cells. By 6‐10 days, distinct features of the subpalisades included: 1) thin portions in lateral walls due to lack of secondary wall depositions at the palisade border; 2) progressive accumulation of fibrous material in numerous vacuoles; and 3) progressive coalescence of osmiophilic bodies and degeneration of cytoplasmic contents. At 21 days, the seeds were dehydrated, mature and hard, but the thin, lateral subpalisade walls were still intact and had not broken. The thin‐walled portions were predetermined weak sites that break, permit palisade separation, expose the area under the blister to available moisture and result in subsequent imbibition of water by the seed. The hydrophilic, fibrous material extruded from the ruptured subpalisade cells may attract water to the newly exposed surface and facilitate penetration of water into the nutritive and embryonic seed tissues.

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Morphological Observations on the Early Imbibition of Water by Sida spinosa (Malvaceae) Seed

Cited by 31 publications

References 13 publications

Taxonomy, anatomy and evolution of physical dormancy in seeds

Taxonomy, anatomy and evolution of physical dormancy in seeds

Functional aspects of mature seed coat of theCannaceae

Development, Structure and Function of Subpalisade Cells in Water Impermeable Sida Spinosa Seeds

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