Variations in abscisic acid, indole-3-acetic acid and zeatin riboside concentrations in two Mediterranean shrubs subjected to water stress

Water stress induced an increase in endogenous concentrations of ABA in Lavandula stoechas L. plants to 13100 pmol ABA g^–1 FW, which may contribute to the maintenance of water relations between the second and the third day of water stress treatment. After the third day, a sharp decrease in ABA levels was observed to 2630 pmol ABA g^–1 FW, together with a decrease in water content and water potential and a loss of plant response to water stress. Water deficit did not induce an increase in endogenous ABA concentration, which remained at 514 pmol ABA g^–1 FW in Rosmarinus officinalis L., which is more sclerophyllous than L. stoechas. Nevertheless, the relative water content of Rosmarinus officinalis L. after seven days of water stress decreased more than 40% and reached values of –3.2 MPa. R. officinalis showed lower levels of ABA, but significantly higher levels of IAA and ZR than L. stoechas (4 times and 6 times respectively in well watered-plants). The increase in ABA levels is not a common mechanism in these two Mediterranean shrubs which survive under water stress conditions.Abbreviations ABA abscisic acid - d days of water stress treatment - DW dry weight - FW fresh weight - IAA indole-3-acetic acid - RP Reversed Phase - RWC relative water content - TW turgid weight - WC water content - ZR zeatin riboside - water potential     

Identification and measurement of indoleacetic and abscisic acids in the cambial region of Picea sitchensis (Bong.) Carr. by combined gas chromatography-mass spectrometry

Indole-3-acetic acid (IAA) and abscisic acid (ABA) were identified by combined gas chromatography-mass spectrometry (GCMS) in fractions obtained by diffusion and extraction from bark peelings of Sitka spruce. A procedure is described for the quantitative analysis of IAA and ABA levels in the same extract using the GCMS technique of single-ion current monitoring. This procedure was used to measure the diffusible, free, and bound fractions of IAA and ABA in the cambial region of Sitka spruce throughout one year; the range in concentration for these fractions was 0.06–0.30, 0.46–3.85, and 0.04–0.20 g/g oven-dry weight, respectively, for IAA, and 0–0.08, 0.03–2.21, and 0.13–0.66 g/g oven-dry weight, respectively, for ABA. Movement in the cambial region was found to be polar for endogenous IAA and nonpolar for endogenous ABA. Recoveries of [¹⁴C]IAA internal standards showed that 73–99.5% of the IAA was lost during purification, and that there could be up to 5-fold differences in recovery between purifications, indicating that IAA loss shold be measured in quantitative analyses.Abbreviations ABA aoscisic acid - GCMS combined gas chromatography-mass spectrometry - IAA indole-3-acetic acid - PVP polyvinylpyrrolidone - SICM single ion current monitoring - TMS trimethylsilyl     

Dynamics of production oftrans-zeatin andtrans-zeatin riboside by immobilized cytokinin-autonomous and cytokinin-dependent tobacco cells

Two strains of cultured tobacco cells (Nicotiana tabacum L. cv. Wisconsin 38) differing in their requirement for exogenous cytokinins (cytokinin-dependent and cytokinin-autonomous) were immobilized on polyphenylenoxide (Sorfix) activated with glutaraldehyde. Columns packed with immobilized cells were continually eluted with diluted Murashige and Skoog's medium lacking or supplemented with synthetic cytokinin (6-benzylaminopurine; BA). Purified samples of column eluates were fractionated by HPLC, andtrans-zeatin (t-Z) andtrans-zeatin riboside (t-ZR) content was estimated by enzyme immunoassay. Both cytokinin-autonomous and cytokinin-dependent tobacco cells produced and excretedt-Z and its riboside, and there were significant quantitative differences between the strains. The steady-state excretion rate oft-Z was 19.8 ng · g^–1 dw · h^–1 and 4 ng · g^–1 dw · h^–1, respectively, and that oft-ZR 4 ng · g^–1 dw · h^–1 and 1 ng · g^–1 dw · h^–1, respectively. Exposure of cytokinin-dependent cells to BA after 72 h of starving for this synthetic cytokinin caused temporary increase in excretion of both zeatin and its riboside. After the application of 5 M BA for 24 h, the excretion rate oft-ZR reached 5 ng · g^–1 dw · h^–1 (5-fold increase), and that oft-Z achieved 12 ng · g^–1 dw · h^–1 (3-fold increase). The elevation oft-Z excretion was delayed about 13 h compared witht-ZR excretion, which started increasing almost immediately after BA application. A pulse of BA in lower concentration (1.5 M for 30 h) provoked lower response.     

Regulation of Stem Abscission and Callus Growth in Shoot Explants of Sweet Orange [Citrus sinensis (L.) Osbeck]

Two-node explants from Sweet Orange cv. St Ives Valencia orangeshoots produced prolific callus and formed secondary abscissionzones within internodes when cultured in vitro with abscisicacid (ABA, 5 µM) or -naphthaleneacetic acid (NAA, 5 µM).Benzyladenine (BA, 1 µm) induced callus but had littleeffect on abscission. Secondary abscission zone formation wasassociated with ABA-induced and auxin-induced ethylene formation.Treatment of explants with inhibitors of ethylene synthesis[aminoethoxyvinyl glycine (AVG), Co²⁺, PO₄^3–] preventedformation of secondary abscission zones but had variable effectson callus formation. Newly made explants contained high concentrationsof endogenous ABA (up to 6000 ng g^–1 f.wt), as measuredby GC/MS/SIM. Long-term subculture of explants (two years) inmedia containing BA (1 µm) led to a reduction in endogenousABA level (40 ng g^–1 f. wt) and to loss of capacity toform extensive callus and secondary abscission zones. Citrus sinensis (L.) Osbeck cv. St Ives Valencia, sweet orange, secondary abscission zones, in vitro, ethylene, endogenous ABA, endogenous IAA     

Changes in Abscisic Acid During Leaf Yellowing of Cut Stock Flowers

Leaf pigments, such as chlorophyll and carotenoids, are essential plant molecules. They provide carbohydrates and energy during all plant life. Leaf pigments are also important parameters of decorative plants, such as floriculture items, cut foliage and flowers. Leaf yellowing is a form of senescence caused by an internal hormone imbalance, such as a lack of cytokinins. The aim of this study was to investigate the changes in total carotenoids and endogenous ABA in cut flower stock leaves during post-harvest life. The effect of pulse treatment with 5 or 10 M thidiazuron (TDZ), 150 mg l^–1 8-hydroxyquinoline sulphate (8-HQS) and combinations of TDZ with 8-HQS on total carotenoids and ABA concentration was also investigated. Results showed that total carotenoids drastically decreased from 1548 g cm^–2, until reaching 565 g cm_–2 at the end of vase life. Endogenous ABA strongly increased at the same time, going from 167 ng g^–1 DW at the beginning of the experiment to 1322 ng g^–1 DW at the end of vase life. The TDZ inhibited carotenoid degradation, but did not affect the ABA concentration, while the 8-HQS did not prevent carotenoid degradation and the ABA concentration was only slightly affected. ABA seems to be a secondary senescence bio-product that may have a synergic effect with other senescence inducers dramatically accelerating leaf senescence.     

Studies on flower longevity in Digitalis

Flower lifespan was terminated by corolla abscission 5–6 days after stigma opening in the unpollinated flower. Increased pollen loads produced increased seed set and reduced flower longevity progressively to a minimum of one day after pollination with pure pollen. Weakening of the abscission zone was detectable 8 h after pollination, whilst the pollen tubes were still within the stigmatic zone, suggesting that a stimulus, moving at 4 mm h^–1 minimum, was transmitted through the style and ovary. Soon after pollination removal of the stigma prevented the pollination-induced corolla abscission. Later it was necessary to remove the stigma and upper style, and later still the whole style to delay abscission. The progressive induction of the stigma and style took place at a rate of 1.5 mm h^–1, in advance of the pollen tubes which grew at 0.75 mm h^–1. It was not possible to reproduce the pollination effects by application of indoleacetic acid (IAA) to the stigma or the style.Abbreviation IAA Indoleacetic acid     

Androgenesis in Citrus aurantifolia (Christm.) swingle

By means of gas chromatography-selected ion monitoring-mass spectrometry using an isotope-dilution assay with 4,5,6,7-tetradeutero-indole-3-acetic acid as the internal standard, indole-3-acetic acid has been estimated to be present in aseptically cultured gametophytes of wild-type Physcomitrella patens (Hedw.) B.S.G. at a level of 0.075 g g^–1 dry weight or 2.1 ng g^–1 fresh weight.Abbreviations IAA indole-3-acetic acid - d₄IAA 4,5,6,7-tetra-deutero-indole-3-acetic acid - [¹⁴C]IAA indole-3-[2-¹⁴C]-acetic acid - GC-SIM-MS gas chromatography-selected ion monitoring-mass spectrometry     

Validation and characterization of a major QTL affecting leaf ABA concentration in maize

A previous study conducted on a maize (Zea mays L.) mapping population derived from Os420 × IABO78 identified a quantitative trait locus (QTL) for leaf-abscisic acid concentration (L-ABA) on chromosome 2 (bin 2.04). In order to validate this QTL, we analyzed with RFLP markers 16 F₄ lines obtained by divergent selection for L-ABA from the same source. Three RFLPs mapping near bin 2.04 showed skewed allelic frequencies; the L-ABA increasing allele (+) was more frequent within the eight lines selected for high L-ABA, while the decreasing allele (–) was more frequent within the eight lines selected for low L-ABA. To characterize more accurately the direct and associated effects of this QTL, near-isogenic lines were developed by molecular marker-assisted back-crossing; four backcross-derived lines were homozygous (+/+) at the QTL and four were (–/–). A pair of near-isogenic hybrids (+/+) and (–/–) at the QTL were also produced. These materials were field tested under water-stressed and well-watered conditions. Across water regimes, the four (+/+) lines averaged a significantly higher mean value than the four (–/–) lines for L-ABA (494 vs. 396 ng ABA g^–1 DW) and a significantly lower mean value for relative water content (90.6 vs. 92.0%). The (+/+) hybrid exceeded the (–/–) for L-ABA (476 vs. 325 ng g^–1 DW) and was less affected by root lodging (44.6 vs. 66.1%). Our results validate the presence of a major QTL for L-ABA on bin 2.04 and indicate that the QTL also affects root traits and relative water content.     

Ethylene-induced leaf abscission in cotton seedlings : the physiological bases for age-dependent differences in sensitivity

The speed of ethylene-induced leaf abscission in cotton (Gossypium hirsutum L. cv LG-102) seedlings is dependent on leaf position (i.e. physiological age). Fumigation of intact seedlings for 18 hours with 10 microliters per liter of ethylene resulted in 40% abscission of the still-expanding third true (3°) leaves but had no effect on the fully expanded first true (1°) leaves. After 42 hours of fumigation with 50 microliters per liter of ethylene, total abscission of the 3° leaves occurred while <50% abscission of the 1° leaves was observed. On a leaf basis, endogenous levels of free IAA in 1° leaves were approximately twice those of 3° leaves. Free IAA levels were reduced equally (approximately 55%) in both leaf types after 18 hours of ethylene (10 microliters per liter) treatment. Ethylene treatment of intact seedlings inhibited the basipetal movement of [¹⁴C]IAA in petiole segments isolated from both leaf types in a dose-dependent manner. The auxin transport inhibitor N-1-naphthylphthalamic acid increased the rate and extent of ethylene-induced leaf abscission at both leaf positions but did not alter the relative pattern of abscission. Abscission-zone explants prepared from 3° leaves abscised faster than 1° leaf explants when exposed to ethylene. Ethyleneinduced abscission of 3° explants was not appreciably inhibited by exogenous IAA while 1° explants exhibited a pronounced and protracted inhibition. The synthetic auxins 2,4-D and 1-naphthaleneacetic acid completely inhibited ethylene-induced abscission of both 1° and 3° explants for 40 hours. It is proposed that the differential abscission response of cotton seedling leaves is primarily a result of the limited abscission-inhibiting effects of IAA in the abscission zone of the younger leaves.     

Indole-3-acetic acid concentration and ethylene evolution during early fruit development in peach

Ethylene evolution was measured from greenhouse-grown Jerseyglo peach fruits beginning 29 days after anthesis. Indole-3-acetic acid (IAA) levels were measured in the pericarp and seed tissues of individual fruits on a single shoot when variable ethylene evolution was noted. Despite hand-pollinating all flowers on the same day, variability within the shoot existed in fruit fresh weight, IAA levels, and ethylene evolution. Seed IAA concentration increased as fruit and seed fresh weight increased and ranged from 106 to 1572 ng. g^–1. As pericarp fresh weight increased, IAA levels in this tissue decreased. Ethylene evolution rates ranged from 0.21 to 1.07 nl. g.^–1 h^–1 and were not correlated with IAA concentration in seed, pericarp, or the whole fruit. High rates of ethylene evolution from the whole fruit occurred prior to increased IAA concentration in the seed.Fruits were excised from field-grown Redskin peach trees beginning 40 days after full bloom. Fruits from field sampled shoots appeared to be more physiologically advanced than the greenhouse-grown Jerseyglo fruits. Pericarp IAA concentration was low, ranging from 2.8 to 6.5 ng. g^–1. Seed concentrations accounted for 75% of the IAA found in the fruit and ranged from 239 to 1042 ng. g^–1. As with greenhouse-grown samples, whole fruit IAA concentration tended to decrease as fruits increased in fresh weight.     

Graviresponsiveness and abscisic-acid content of roots of carotenoid-deficient mutants of Zea mays L.

The abscisic-acid (ABA) content of roots of the carotenoid-deficient w-3, vp-5, and vp-7 mutants of Z. mays was analyzed using gas chromatography-mass spectrometry with an analysis sensitivity of 6 ng ABA g^–1 fresh weight (FW). Roots of normal seedlings of the same lines were characterized by the following amounts of ABA (as ng ABA g^–1 FW,±standard deviation): w-3, 279±43; vp-5, 237±26; vp-7, 338±61. We did not detect any ABA in roots of any of the mutants. Thus, the lack of carotenoids in these mutants correlated positively with the apparent absence of ABA. Primary roots of normal and mutant seedlings were positively gravitropic, with no significant differences in the curvatures of roots of normal as compared with mutant seedlings. These results indicate that ABA 1) is synthesized in maize roots via the carotenoid pathway, and 2) is not necesary for positive gravitropism by primary roots of Z. mays.Abbreviation ABA abscisic acid     

Preharvest application of exogenous abscisic acid (ABA) or an ABA analogue does not affect endogenous ABA concentration of onion bulbs

Bulb abscisic acid (ABA) concentration has been shown to decrease in stored onions, and onset of sprouting to occur at minimal ABA concentration. It was postulated that increasing prestorage bulb ABA concentration could increase storage life. Analogues of ABA that enhance biological activity and resist degradation are available and are becoming commercially viable. Exogenous ABA and an ABA analogue (8′-methylene ABA methyl ester; PBI-365) were applied separately as preharvest foliar sprays to six onion cultivars with varying storage potential. Quality indicators including pyruvate, total soluble solids and firmness were determined at regular intervals during storage. Neither ABA treatment increased endogenous bulb ABA concentration. Bulb ABA concentration decreased during storage and the onset of sprouting occurred at a minimal ABA concentration (ca. 50–120 ng g⁻¹ DW). This was followed by an increase in ABA concentration as sprout growth continued. No straightforward relationship between ABA and carbohydrate metabolism could be determined.     

Effects of water stress on cellular ultrastructure and on concentrations of endogenous abscisic acid and indole-3-acetic acid in Fatsia japonica leaves

Ultrastructural alterations in mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in water-stressed field-grown plants of Fatsia japonica. Under water deficit cellular membranes were modified and an increase in vesicles was observed. The main damage to the chloroplasts included thylakoid swelling and disruption of the chloroplast envelope. Concomitant variations in abscisic acid and indole-3-acetic acid were observed. Despite the expected increased in endogenous ABA concentration in relation to water stress, after the highest concentration of ABA, observed at predawn in severely stressed plants (29-1), there was a sharp decline from 2768 pmol g fw^–1 to 145 pmol g fw^–1; thus in severely stressed plants ABA levels were not related to changes in bulk leaf ABA contents. Water stress did not influence the concentrations of indole-3-acetic acid, although the increase in the endogenous abscisic acid concentration could be related with the ultrastructural changes.Abbreviations ABA abscisic acid - IAA indole-3-acetic acid - leaf water potential     

UDP-Glucuronosyltransferase activity is correlated to saponin production in Gypsophila paniculata root in vitro cultures

UDP-Glucuronosyltransferase (UGT, EC 2.4.1.17) activity was detected in excised root cultures of Gypsophila paniculata. The UGT activity (up to 0.8 nkat mg^–1 protein) correlated to the total saponin content (2 mg g^–1 dw) during the exponential phase of the batch culture. This gives rise to the hypothesis of a direct relationship in the biosynthetic pathway regulation between the enzyme activity and the saponin biosynthesis.     

Role of ABA in stamen and pistil development in the normal and solanifolia mutant of tomato (Lycopersicon esculentum)

Summary The role of abscisic acid (ABA) in stamen and pistil development of the normal and solanifolia (sf/sf) mutant of tomato (Lycopersicon esculentum Mill.) was analyzed. The solanifolia mutant produces flowers with separate floral organs, unlike the fused organs of normal flowers, and has greater number of carpels and locules per ovary than the normal. Applications of 10^–5 M ABA to normal floral buds produced flowers with separate stamens, but higher concentrations (10^–4 M ABA) resulted in the complete suppression of stamen growth or stamens that were devoid of anthers. ABA at both 10^–4 and 10^–5 M also induced an increase in the number of carpels and locules in normal flowers, but not in mutant ones. Analysis of endogenous ABA by a radioimmunoassay revealed that the pistils of mutant flowers contained a significantly higher level of ABA than those of normal flowers, but there was no difference in the ABA content of the stamens. The non-fusion of the stamens and the high number of carpels and locules in solanifolia mutant flowers may be explained by the high level of ABA in the floral apex during the initiation and development of carpels.     

Carbonic Anhydrase,Photosynthesis, and Seed Yield in Mustard Plants Treated with Phytohormones

The leaves of 30-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10^–6 M aqueous solutions of indole-3-yl-acetic acid (IAA), gibberellic acid (GA₃), kinetin (KIN), and abscisic acid (ABA) or 10^–8 M of 28-homobrassinolide (HBR). All the phytohormones, except ABA, improved the vegetative growth and seed yield at harvest, compared with those sprayed with deionised water (control). HBR was most prominent in its effect, generating 32, 30, 36, 70, 25, and 29 % higher values for dry mass, chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) activity, and net photosynthetic rate in 60-d-old plants, pods per plant, and seed yield at harvest, over the control, respectively. The order of response to various hormones was HBR > GA₃ > IAA > KIN > control > ABA.     

Abscisic (ABA)-Aldehyde Is a Precursor to, and 1',4'-trans-ABA-Diol a Catabolite of, ABA in Apple

Previous ¹⁸O labeling studies of abscisic acid (ABA) have shown that apple (Malus domestica Borkh. cv Granny Smith) fruits synthesize a majority of [¹⁸O]ABA with the label incorporated in the 1′-hydroxyl position and unlabeled in the carboxyl group (JAD Zeevaart, TG Heath, DA Gage [1989] Plant Physiol 91: 1594-1601). It was proposed that exchange of ¹⁸O in the side chain with the medium occurred at an aldehyde intermediate stage of ABA biosynthesis. We have isolated ABA-aldehyde and 1′-4′-trans-ABA-diol (ABA-trans-diol) from ¹⁸O-labeled apple fruit tissue and measured the extent and position of ¹⁸O incorporation by tandem mass spectrometry. ¹⁸O-Labeling patterns of ABA-aldehyde, ABA-trans-diol, and ABA indicate that ABA-aldehyde is a precursor to, and ABA-trans-diol a catabolite of, ABA. Exchange of ¹⁸O in the carbonyl of ABA-aldehyde can be the cause of loss of ¹⁸O from the side chain of [¹⁸O]ABA. Results of feeding experiments with deuterated substrates provide further support for the precursor-product relationship of ABA-aldehyde → ABA → ABA-trans-diol. The ABA-aldehyde and ABA-trans-diol contents of fruits and leaves were low, approximately 1 and 0.02 nanograms per gram fresh weight for ABA-aldehyde and ABA-trans-diol, respectively, while ABA levels in fruits ranged from 10 to 200 nanograms per gram fresh weight. ABA biosynthesis was about 10-fold lower in fruits than in leaves. In fruits, the majority of ABA was conjugated to β-d-glucopyranosyl abscisate, whereas in leaves ABA was mainly hydroxylated to phaseic acid. Parallel pathways for ABA and trans-ABA biosynthesis and conjugation in fruits and leaves are proposed.     

Characterization of phytohormonal and postharvest senescence responses of balsam fir (Abies balsamea (L.) Mill.) exposed to short-term low temperature

To fulfill the US Thanksgiving and Christmas tree markets, balsam fir (Abies balsamea (L.) Mill.) is generally harvested before the cold season, anecdotally leading to premature needle senescence. Accordingly, we tested the hypothesis that LT exposure before harvest induces specific hormonal changes and delays postharvest senescence and/or abscission in balsam fir. Two hundred and six seedlings exposed to two temperature treatments for 48?h, LT at 5?°C and controls at 22?°C were severed off roots and monitored for their postharvest needle senescence. Root and shoot (needles and buds) tissues were examined for major endogenous hormone metabolites. LT increased shoot ABA (2,007?ng?g^?1 DW) by 2.5× and decreased GA₄₄ (9.84?ng?g^?1 DW) by 3.5× over those in roots. LT did not alter cytokinins, auxins or any root hormonal concentration. With auxins, only IAA, IAA-Asp, IAA-Leu and IAA-Glu were detected and the concentrations of IAA and IAA-Asp in shoots were lower than those found in roots. Among cytokinins, shoot c-ZR (58.95?ng?g^?1 DW) and t-ZR (4.17?ng?g^?1 DW) were 3× higher than those in roots. Apart from GA₄₄, GA₉ (136.76?ng?g^?1 DW) was abundant in shoots. The PBL and PNL were 46 and 1.2?%, irrespective of treatments. LT seedlings held needles 11?days longer than the controls (122?days). In balsam fir, short-term LT exposure augmented ABA and decreased GA₄₄ levels in shoots and delayed postharvest needle senescence.     

Changes in indole-3-acetic acid and abscisic acid levels during tomato (Lycopersicon esculentum Mill.) fruit development and ripening

Changes in the levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) in tomato (Lycopersicon esculentum Mill.) fruit pericarp tissue during development through ripening were measured by GC-SIM-MS using d₃-ABA and ¹³C₆-IAA internal standards. In the two cultivars of fieldgrown tomatoes analyzed, the highest IAA levels (8–24 ng/g fw) were found at the earliest stage of development (7 days after anthesis) followed by a rapid decline in levels of the hormone. ABA levels of 40–60 ng/g fw were found at the earliest stages of development followed by a decline in levels until ripening occurred when elevated ABA levels (125 ng/g fw) were measured.     

Microphytic standing stocks at Kerguelen Islands (Subantarctic,Indian Ocean), annual variations in relation to environmental factors: II,intertidal and subtidal microphytobenthos

The microphytobenthic standing crop in marine coastal sediments from Kerguelen main island (from surface to 8 cm deep) varied in relation to the tidal position, grain size, and shelter of sediments. A time-series analysis was performed at three distinct sites: a sheltered fjord (PRAY), a moderately exposed embayment (PAF) and a deep fjord with higher open-ocean influence (PN). Temporal variations on all studied parameters were observed on intertidal, as well as on subtidal sediments, but with a great range in variations and pattern. Compared to phytoplankton blooms at the same location and stations, the microphytobenthos productive periods were not so marked, especially on intertidal sediments. Nevertheless, high productivity periods were in most cases linked to austral spring and summer (up to 30–50 g Chl a g^–1 dw, in intertidal sheltered sands; >170 g Chl a g^–1 dw, in sheltered subtidal muds). On subtidal muddy sites, the high phaeopigments concentrations (up to 195 g Phaeo a g^–1 dw at PRAY site) were attributed to kelp and epiphyte degradation and sedimentation, and also to macrofauna trophic influence, whereas at Portes-Noires fjord (PN) a Phaeophytine a late spring increase in 1991 was suspected to be of plankton origin. The PN site exhibited a lower productivity than at the other two sites, regardless of the tidal position of the sediment, due to a delayed annual cycle in surficial temperature and standing crop. Compared to the phytoplankton blooms, the microphytobenthos productivity at Kerguelen main island was less restricted in time and may occur throughout the year, not just to the benefit of the benthos food-chain, but also to the pelagic one via resuspension, as well as to filter feeders (i.e. mussels).