Response of the recalcitrant seeds of Avicennia marina to hydrated storage: events occurring at the root primordia

AbstractThis study was undertaken to test the hypotheses that germinative metabolism of recalcitrant seeds in storage induces a requirement for additional water, which may result in the development of mild water stress, and that a reduction of the rate of this germinative metabolism will increase the storage lifespan of recalcitrant seeds. Studies were undertaken on seeds of Avicennia marina (Forssk.) Vierh. and concentrated on root primordia as these constitute the tissue that undergoes most change during storage. Encapsulating seeds from which the pericarp had been removed (naked seeds) in an alginate gel increased storage lifespan fourfold compared with naked seeds. Measures of metabolic rate such as time to first germination in storage and rate of protein synthesis did not indicate differences between alginate-coated and naked seeds, although ultrastructural observations indicated that both germinative and deteriorative processes were occurring more slowly in the alginate-coated seeds. Measures of water content and water and turgor potentials did not reveal signs of a mild water stress in either treatment. However, the number of seeds visibly contaminated with fungi and the rapidity with which this contamination became apparent were much reduced in alginate-coated seeds. It is suggested that fungal contamination constitutes a major cause of deterioration in stored, hydrated seeds of A. marina (and possibly other recalcitrant seed species) and the main effect of the alginate coating was to reduce the incidence of fungal contamination.

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Seed development in relation to desiccation tolerance: A comparison between desiccation-sensitive (recalcitrant) seeds of Avicennia marina and desiccation-tolerant types

Seed Science Research ◽

10.1017/s0960258500001513 ◽

1993 ◽

Vol 3 (1) ◽

pp. 1-13 ◽

Cited By ~ 73

Author(s):

Jill M. Farrant ◽

N. W. Pammenter ◽

Patricia Berjak

Keyword(s):

Seed Development ◽

Seedling Establishment ◽

Soluble Sugars ◽

Avicennia Marina ◽

Sensu Stricto ◽

Starch Accumulation ◽

Recalcitrant Seeds ◽

Recalcitrant Seed ◽

Orthodox Seeds

AbstractDevelopment of the highly desiccation-sensitive (recalcitrant) seeds of primarily one species, Avicennia marina, is reviewed and compared with the ontogeny of desiccation-tolerant (orthodox) seeds. A. marina seeds undergo no maturation drying and remain metabolically active throughout development, which grades almost imperceptibly into germination. While PGR control of histodifferentiation is essentially similar to that characterizing desiccation-tolerant seeds, the phase of growth and reserve deposition is characterized by exceedingly high cytokinin levels which, it is proposed, promote a sink for assimilate import. While some starch accumulation does occur, the predominant reserves are soluble sugars which are readily available for the immediate onset of seedling establishment upon shedding. ABA levels are negligible in the embryo tissues during seed maturation, but increase in the pericarp, which imposes a constraint upon germination until these outer coverings are sloughed or otherwise removed. The pattern of proteins synthesized remains qualitatively similar throughout seed development in A. marina, and no LEA proteins are produced. This suggests both that seedling establishment is independent of maturation proteins and that the absence of LEAs and desiccation sensitivity might be causally related. The study on A. marina reveals that for this recalcitrant seed-type, germination per se cannot be defined: rather, it is considered as the continuation of development temporarily constrained by the pericarp ABA levels. This leads to a reexamination of the role of rehydration as key event sensu stricto, in the germination processes in desiccation-tolerant (orthodox) seeds.

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Photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress

Acta Amazonica ◽

10.1590/s0044-59672014000100007 ◽

2014 ◽

Vol 44 (1) ◽

pp. 67-77 ◽

Cited By ~ 2

Author(s):

Gracilene Fernandes da Costa Azevedo

Keyword(s):

Water Stress ◽

Higher Plants ◽

Field Capacity ◽

Outdoor Exposure ◽

Photosynthetic Parameters ◽

Bertholletia Excelsa ◽

Full Sunlight ◽

Carapa Guianensis ◽

Light Levels ◽

Mild Water Stress

Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (ΨL) of -500 to -700 kPa) and without water stress (WWS, ΨL of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.

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A new approach towards the so-called recalcitrant seeds

Journal of Seed Science ◽

10.1590/2317-1545v40n3207201 ◽

2018 ◽

Vol 40 (3) ◽

pp. 221-236 ◽

Cited By ~ 10

Author(s):

Claudio José Barbedo

Keyword(s):

Plant Conservation ◽

Point Of View ◽

Recalcitrant Seeds ◽

New Approach ◽

Recalcitrant Seed ◽

Seed Conservation ◽

Conservation Technology ◽

Orthodox Seeds ◽

Standard Life ◽

Life Behavior

ABSTRACT: Water is essential, irreplaceable, and indispensable for any kind of carbon-based-life metabolic activity. Water-dependent living beings are the expected pattern in nature. However, some organisms can survive for some time at a minimum water content, such as seeds of some species (orthodox seeds). Nevertheless, the expected standard life behavior is found in seeds of another group of species, the so-called recalcitrant seeds, which are sensitive to desiccation. A huge range of different behaviors can be found between these two groups, leading authors to consider that orthodoxy and recalcitrance is not an all-or-nothing situation. Notwithstanding, we are still too far from understanding the differences and similarities between all these kinds of seeds and this has been a serious barrier to the development of plant conservation technologies. A new approach to understanding the differences between these seeds is presented here based on seed maturation, environmental influences, and evolution. From this point of view, all kinds of seed behavior are contemplated and, consequently, some new perspectives are considered for the recalcitrant seed conservation technology, the most intensely desired technology nowadays in this area.

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Desiccation and survival in the recalcitrant seeds of Avicennia marina: DNA replication, DNA repair and protein synthesis

Seed Science Research ◽

10.1017/s0960258500000350 ◽

2000 ◽

Vol 10 (3) ◽

pp. 307-315 ◽

Cited By ~ 16

Author(s):

Ivan Boubriak ◽

Mariuccia Dini ◽

Patricia Berjak ◽

Daphne J. Osborne

Keyword(s):

Dna Repair ◽

Protein Synthesis ◽

Dna Replication ◽

Dna Fragmentation ◽

Water Loss ◽

Avicennia Marina ◽

Root Tips ◽

Root Primordia ◽

Mangrove Species ◽

Temporary Reduction

Abstract An autoradiographic study was made of leucine and thymidine incorporation into the meristematic root primordia and hypocotyl tips of seeds of the recalcitrant mangrove species, Avicennia marina. The investigations show that although there is a temporary reduction of protein synthesis at shedding, root primordia and surrounding hypocotyl cells of the axis never wholly cease incorporation of [3H]leucine and regain pre-shedding levels of activity within a day. Precursor studies using methyl-[3H]thymidine show that, at shedding, there is a temporary cessation of incorporation into root meristem nuclei that lasts no longer than 48 h and, within a day, pre-shedding levels are regained in the meristem nuclei. Analysis of DNA fragmentation patterns in root tips at the time of shedding, and their ability to repair radiation-induced DNA damage, indicate that DNA repair processes are markedly compromised in these cells if water loss reaches 22%. Protein synthesis and DNA replication are reduced by more than half by a water loss of 18% and 16%, respectively. DNA replication does not fully recover on rehydration after only 8% water loss. DNA fragmentation to nucleosomes indicates a programme of cell death at a water loss of 10%. We suggest that the feature of continuous protein synthesis activity with only a temporary interruption in active cell cycling in A. marina root primordia helps to explain both the rapidity in seedling establishment and the extreme vulnerability to desiccation.

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