Tissue Partitioning During Leaf Development in Ornamentally-grown Frithia pulchra (Mesembryanthemaceae), a 'Window Plant'

Young (i.e. 5-mm long) leaves of the window-plant Frithia pulchra(Mesembryanthemaceae) allocate approx, 21 % of their volumeto epidermis, 49 % to chlorenchyma, and 29 % to window tissue.By the time leaves are 25 mm long, the relative volumes of epidermisand chlorenchyma decrease to approx, 7 and 27 % respectively.During the same period, the relative volume of window tissueincreases from 29 to 66 %. The relative volumes of epidermis,window, and chlorenchyma tissues do not change as leaf lengthincreases from 25 to 57 mm. These results indicate that earlystages of leaf development in F. pulchra involve preferentialreallocations of volume to different tissues, whereas laterstages of leaf development involve uniform expansion of allof the leaf's tissues (i.e. the relative volumes of tissuesdo not change). The relative volumes of epidermis and windoware always largest in the lower third of a leaf. The relativevolume of chlorenchyma is largest in the upper third of youngleaves but becomes constant in the upper two thirds of leavesduring later stages of development. These results, indicatingthat leaves and tissues of F. pulchra are asymmetric and developpolarly, are discussed relative to corresponding studies ofcellular size and leaf structure. Frithia pulchra, leaf development, Mesembryanthemaceae, stereology, window plant     

Ochna pulchra Hook: Leaf Growth and Development Related to Photosynthetic Activity

Ochna pulchra Hook. is a deciduous broad-leaved tree in theMixed Bushveld vegetation of the Northern Transvaal. The growthand development of leaves taken from trees in the field werestudied from a stage shortly before bud break, in late spring,until they were fully expanded and at the peak of photosyntheticactivity. Leaf area was measured by photographing the leaf against a transparentmm² grid. Finally a constant relationship between leaf area(A) and the linear dimension of length (L) and breadth (B) wasestablished: A = b x LB, where coefficient b = 0.72. Transverse sections of the lamina of the youngest leaves showeda five-layered plate meristem with a few functional conductingelements in the midrib. During further leaf development, celldivision was followed by means of autoradiography using [³H]thymidine.It was most active during the week after bud break. Leaf cell increment following on cell division made the majorcontribution to leaf growth resulting in a lamina that was atleast 90% expanded 4 weeks after bud break. The histologicalchanges accompanying cell division were observed using lightand electron microscopy. Even in late stages of leaf development mature and differentiatingstomata occurred together, limited to the abaxial epidermisand the midrib. Scanning electron microscopy showed stomataldistribution, their increasing density and gradual opening.The structure of these sunken stomata could reduce the outwarddiffusion of water vapour and increase the diffusion resistanceto carbon dioxide. Carbon assimilation rates of the developing leaves were measuredusing an IRGA (infra-red gas analyser) and their chlorophyllvalues were calculated. Photosynthesis was first measured amonth after bud break when the leaves were fully expanded, over50 % of the stomata exposed and leaf mesophyll tissue differentiatedwith mature chloroplasts. Net photosynthetic rates and chlorophyllvalues peaked 1 month later. Ochna pulchra Hook., photosynthesis, leaf development, leaf area, stomata, chlorophyll, savanna     

Cellular Structure and Light Absorbtion in Leaves of Frithia pulchra (Mesembryanthemaceae)

In order to quantify the structural differences between celltypes of leaves from a ‘ window’ plant, an ultrastructuralmorphometric analysis was made of the epidermal, window andchlorenchyma tissues of Frithia pulchra. Epidermal cells arethe largest cells found in Frithia leaves and are characterizedby the presence of a thick outer tangential cell wall and numerousvacuolar inclusions. Epidermal tissue has an optical densityof 0.30. The transparent window tissue (i.e. optical density= 0.08) has a uniform ultrastructure throughout the length ofthe leaf. The vacuome comprises aproximately 97 per cent ofthe protoplasmic volume of window cells. Chlorenchyma cellspossess thin cell walls and are surrounded by numerous intercellularspaces. Cells of the apical chlorenchyma tissue possess approximately30 plastids per cell. These chloroplasts have an average individualvolume of 220 µm². Cells of the basal chlorenchyma tissuecontain chloroplasts that are five to six times smaller andmore numerous than those in cells of the apical chlorenchyma.The increased volume of chloroplasts in the apical comparedwith basal chlorenchyma cells (i.e. 31.4 and 20.2 per cent ofthe protoplasm, respectively) is positively correlated withtheir optical densities of 1.46 and 0.97, respectively. Frithia pulchra, stereology, leaf, light absorption, window plant     

Coexistence and interference between a native perennial grass and non-native annual grasses in California

Little is known about the potential for coexistence between native and non-native plants after large-scale biological invasions. Using the example of native perennial bunchgrasses and non-native annual grasses in California grasslands, we sought to determine the effects of interference from non-native grasses on the different life stages of the native perennial bunchgrass Nassella pulchra. Further, we asked whether N. pulchra interferes with non-native annual grasses, and whether competition for water is an important component of these interspecific interactions in this water-limited system. In a series of field and greenhouse experiments employing neighbor removals and additions of water, we found that seedling recruitment of N. pulchra was strongly seed-limited. In both field and greenhouse, natural recruitment of N. pulchra seedlings from grassland soil was extremely low. In field plots where we added seeds, addition of water to field plots increased density of N. pulchra seedlings by 88% and increased total aboveground N. pulchra seedling biomass by almost 90%, suggesting that water was the primary limiting resource. In the greenhouse, simulated drought early in the growing season had a greater negative effect on the biomass of annual seedlings than on the seedlings of N. pulchra. In the field, presence of annuals reduced growth and seed production of all sizes of N. pulchra, and these effects did not decrease as N. pulchra individuals increased in size. These negative effects appeared to be due to competition for water, because N. pulchra plants showed less negative pre-dawn leaf water potentials when annual neighbors were removed. Also, simply adding water caused the same increases in aboveground biomass and seed production of N. pulchra plants as removing all annual neighbors. We found no evidence that established N. pulchra plants were able to suppress non-native annual grasses. Removing large N. pulchra individuals did not affect peak biomass per unit area of annuals. We conclude that effects of interference from non native annuals are important through all life stages of the native perennial N. pulchra. Our results suggest that persistence of native bunchgrasses may be enhanced by greater mortality of annual than perennial seedlings during drought, and possibly by reduced competition for water in wet years because of increased resource availability. Received: 12 November 1998 / Accepted: 4 August 1999     

rpoB-Based Microbial Community Analysis Avoids Limitations Inherent in 16S rRNA Gene Intraspecies Heterogeneity

Contemporary microbial community analysis frequently involves PCR-amplified sequences of the 16S rRNA gene (rDNA). However, this technology carries the inherent problem of heterogeneity between copies of the 16S rDNA in many species. As an alternative to 16S rDNA sequences in community analysis, we employed the gene for the RNA polymerase beta subunit (rpoB), which appears to exist in one copy only in bacteria. In the present study, the frequency of 16S rDNA heterogeneity in bacteria isolated from the marine environment was assessed using bacterial isolates from the red alga Delisea pulchra and from the surface of a marine rock. Ten strains commonly used in our laboratory were also assessed for the degree of heterogeneity between the copies of 16S rDNA and were used to illustrate the effect of this heterogeneity on microbial community pattern analysis. The rock isolates and the laboratory strains were also used to confirm nonheterogeneity of rpoB, as well as to investigate the versatility of the primers. In addition, a comparison between 16S rDNA and rpoB PCR-DGGE (denaturing gradient gel electrophoresis)-based community analyses was performed using a DNA mixture of nine isolates from D. pulchra. Eight out of 14 isolates from D. pulchra, all rock isolates, and 6 of 10 laboratory strains displayed multiple bands for 16S rDNA when analyzed by DGGE. There was no indication of heterogeneity for either the rock isolates or the laboratory strains when rpoB was used for PCR-DGGE analysis. Microbial community pattern analysis using 16S rDNA PCR-DGGE showed an overestimation of the number of laboratory strains in the sample, while some strains were not represented. Therefore, the 16S rDNA PCR-DGGE-based community analysis was proven to be severely limited by 16S rDNA heterogeneity. The mixture of isolates from D. pulchra proved to be more accurately described using rpoB, compared to the 16S rDNA-based PCR-DGGE.     

Restoration of Stipa pulchra Grasslands: Effects of Mycorrhizae and Competition from Avena barbata

Experiments were conducted in the field and the greenhouse to determine whether vesicular-arbus-cular mycorrhizae affect growth and competition between the native perennial Stipa pulchra and the introduced annual Avena barbata. Soils in the greenhouse were steam-sterilized, and in the field they were treated with the fungicide benomyl. Stipa pulchra showed decreased shoot dry mass and increased root mass when inoculated, while A. barbata showed the opposite response, increased shoot mass and decreased root mass. Mycorrhizal A. barbata also produced more seeds. Mycorrhizae did not alleviate the negative effects of competition of A. barbata on S. pulchra, as has been demonstrated for other pairs of weedy and nonweedy species. The same three species of mycorrhizal fungi were present in annual and perennial grasslands, but their relative composition was different. When inoculum from the two grassland types were tested in the field, the fungal species began to revert within five months to the species composition found in grasslands of the host plant. This indicates that, once annual grassland has been revegetated with the native S. pulchra, the original fungal species composition may return relatively quickly. Where A. barbata dominates, inoculation with mycorrhizal fungi alone will not suffice for establishing S. pulchra, and the usual practices for control of weed competition need to be employed.     

FEED PREFERENCES OF NUCELLA CRASSILABRUM AND JUVENILE CONCHOLEPAS CONCHOLEPAS (GASTROPODA: MURICIDAE) FROM A ROCKY SHORE IN SOUTHERN CHILE

The feeding preferences of two molluscan predators, Nucellacrassilabrum and Concholepas concholepas, from southern Chilewere studied by means of laboratory and field experiments. Bothpredators preferred Semimytilus algosus to Perumytilus purpuratus.Small C. concholepas selected mussels less than 5 mm, similarsized N. crassilabrum preferred individuals of 5-10 mm. LargerC. concholepas did not consume mussels above 10 mm whereas largeN. crassilabrum preferred the 15-20 mm size but also took musselsup to 30 mm. Individuals rarely consumed more than one musselin a 7 day period. Both predators consumed the barnacle Chthamalusscabrosus, larger items being taken more frequently than smallerones. Field experiments confirmed laboratory results, but barnacleconsumption was 30% higher in the field. Although considerabledietary overlap is evident between these two predators, thereare clear differences in their selection of prey species andsizes. This might provide a mechanism for reducing competitionwhich may result from changes in prey abundance. (Received 17 July 1990; accepted 28 August 1990)     

转Bt基因水稻对两种弹尾虫及尖钩宽黾蝽捕食作用的影响

转Bt基因水稻KMD1、KMD2和对照水稻XS11稻田主要有两种弹尾虫：灰橄榄长角跳虫 Entomobryagriseoolivata (Packard) 和钩圆跳虫 Bourletiella christianseni Banks。两种Bt稻田中灰橄榄长角跳虫种群密度均显著高于对照XS11稻田;在以KMD1和KMD2腐烂 茎叶为食的灰橄榄长角跳虫成虫中检测到微量Cry1Ab杀虫蛋白。室内测定结果表明,不管是单 头捕食还是多头协同捕食,尖钩宽黾蝽Microvelia horvathi Lundblad 成虫对用3种供试 水稻残体饲养的灰橄榄长角跳虫的捕食量和功能反应均符合HollingⅡ型方程,其日捕食量、瞬 时攻击率（a）和处理时间（T_h）均无显著差异。     

Pairing success of male Gammarus lacustris infected by two acanthocephalans: a comparative study

The costs of parasitism to host reproduction can be best assessedusing field studies to determine overall mating success andexperimental studies to examine how parasites may affect matingbehavior. We compared the influence of two parasites, Polymorphusparadoxus and P. marilis (Acanthocephala), on the pairing successof their intermediate host (Gammarus lacustris, Crustacea) inboth the field and laboratory. Parasitism significantly loweredthe pairing success of male gammarids. In the field, P. paradoxus-infectedmales paired significantly less often than P. marilis-infectedor uninfected males. Those infected by P. marilis were alsofound in precopula significandy less often than uninfected ones.In the laboratory, the pairing success of males infected byeither parasite was significantly reduced in both competitiveand noncompetitive situations. As in the field studies, thepairing success of P. paradoxus-infected males was significantlylower than that of P. marilis-infected and uninfected males.Polymorphus marilis-infected males were also outcompeted byuninfected individuals, however, their pairing success improvedwhen alone with a female (noncompetitive experiments). We relatethe differential influence of the two parasites on the pairingsuccess of male gammarids to their effects on the physiologyand behavior of G. lacustris.     

Integrating development and environment to model reproductive performance in natural populations of an intertidal gastropod

Functional challenges can differ among life-history stages,yet performance at one stage may be linked to the outcome ofperformance at others. For example, adult performance, in termsof the location or timing of reproduction in response to environmentalsignals, can set conditions that affect the performance of developmentalstages. In marine invertebrates, however, early performancehas been studied primarily in the laboratory. I outline an integrativeapproach to the study of field reproductive performance in amarine gastropod that undergoes development in intertidal habitats.Embryos within gelatinous masses experience high variabilityin development temperature and frequent exposure to thermalstress. In laboratory experiments, developmental performancewas measured as a function of maximum temperature (T_max) experiencedduring fluctuations that mimicked field tidal profiles. Performancecurves showed declines that coincided with temperature thresholdsfor heat shock protein (Hsp) expression, a signal of cellularstress. Application of laboratory results to field records ofT_max predicted large variation in the survival of embryos depositedon different days. Timing of field reproduction was non-randomwith respect to T_max, suggesting that adults could help to bufferembryos from environmental stress. Embryo survival, however,was not predicted to benefit from the non-random pattern ofadult reproduction. Adults may be constrained to respond toinformation that only weakly predicts conditions that embryoswill experience. Studies that incorporate linkages between lifecycle stages in the field may better reveal how performancecapacities and constraints at one stage can influence performanceand selection at others.     

OTHER PAPERS: INTERFERENCE AND RESOURCE COMPETITION IN TWO LAND SNAILS: ADULTS INHIBIT CONSPECIFIC JUVENILE GROWTH IN FIELD AND LABORATORY

Interference and resource competition by adults inhibited growthrates of conspecific juveniles of the land snail species Mesodonthyroidus and Neohelix albolabris in separate field and laboratoryexperiments, but not in laboratory experiments on Anguispiraalternata. In 1 m² field cages at near-natural densities underambient food and water conditions, juvenile M. thyroidus apparentlycompeted with adults for food or water or both resources, growingmore slowly when living with two conspecific adults, but beingunaffected by adult presence when food and water were augmented.Neohelix albolabris juveniles were similarly unaffected in fieldcages by presence of two adults when food and water were augmented.In contrast, interference, not resource competition, apparentlyexplained growth inhibition in laboratory cages at densitiesconsiderably greater than natural densities, with non-limitingfood and moisture; both M. thyroidus and N. albolabris juvenilesgrew more slowly as conspecific adult number increased fromzero to three. (Received 17 July 1995; accepted 11 November 1996)     

Effects of fish presence and simulated moonlight gradients on night-time horizontal movements of a predatory zooplankter, Chaoborus punctipennis

Some zooplankton, including Chaoborus punctipcnnis, have recentlybeen reported to undergo die1 horizontal migrations in additionto their widely known vertical migrations. In a series of laboratoryand field experiments, we tested the influences of gradientsin light intensity and fish presence on horizontal migrationin C.Punctipennis. In a small chamber, C.punctipennis showedno response to simulated moonlight gradients. They did, however,show significant movement away from fish held at one end ofthe chamber under uniform moonlight. A field experiment in alarge chamber indicated that the response to fish was inducedby chemical cues. When tested in the laboratory chamber withboth moonlight gradients and fish present, C.punctipennis becamepositively phototactic. This response increased the movementaway from fish when the fish were at the darker end of the gradient,or reduced it when the fish were at the brighter end. Ln combination,these experiments demonstrate that C.punctipennis show directedhorizontal movements in response to fish presence and moonlightgradients, suggesting a potential for these stimuli to influencehorizontal migrations observed in the field. Present address: Department of Biology, University of CaliforniaLos Angeles, CA 90095-1606, USA     

High genetic diversity among fossorial lizard populations (Anniella pulchra) in a rapidly developing landscape (Central California)

California is a biodiversity hotspot facing unbridled human population growth, especially in Central California. One of the poorly known, sensitive species in this area is the California legless lizard (Anniella pulchra), a fossorial worm-like reptile. We report mt and nuDNA sequences from 69 museum-vouchered samples of Anniella (A. pulchra and its sister species A. geronimensis) from 48 localities. Our genetic survey reveals substantially more genetic diversity within A. pulchra than previously reported. Our two independently evolving markers (mt and nuDNA) reveal five major lineages of A. pulchra. Two of the five major lineages of A. pulchra correspond to a north-south split found in other widespread California reptiles. These northern and southern clades also correspond to a previous study showing variation in chromosomal number. Unlike most other Californian reptiles, A. pulchra has major genetic lineages that are endemic to Central California including two that are endemic to the San Joaquin Valley and Carrizo Plain. Although A. pulchra is threatened throughout its range, the distinct San Joaquin lineages are seriously imperiled by urban sprawl. Some of the localities for the newly recognized genetic lineages have already been destroyed by development.     

Harvest rates and foraging strategies in Negev Desert gerbils

We examined the foraging strategy and quantified the foragingtraits of two nocturnal rodent species, Allenby's gerbil (Gerbillusallenbyi) and the greater Egyptian sand gerbil (Gerbillus pyramidum).In the laboratory, both species used two distinct foragingstrategies: either they immediately consumed seeds found ina patch (seed tray); or they collected and delivered the seedsto their nest box for later consumption. Moreover, we founda transition in foraging strategy among individual G. allenbyi under laboratory conditions; they all began by consuming theseeds on the tray and, after 7 days on average, switched tothe collecting strategy. By contrast, in the field both speciesused only one foraging strategy; they collected and deliveredthe seeds to their burrow or to surface caches for later consumption.Furthermore, G. allenbyi and G. pyramidum collected seeds atsignificantly higher rates in the field than in the laboratorybecause the seed encounter rates for both species were higherin the field. This suggests that in natural conditions, probablyinvolving predation risk and competitive pressure, gerbilsmust respond in two ways: (1) they must choose a foraging strategythat reduces predation risk by minimizing time spent feedingoutside their burrows; and (2) they must forage more efficiently.In the field, seed handling time of the larger species, G. pyramidum, was shorter than that of the smaller one, G. allenbyi.This difference may give G. pyramidum an advantage when resourcelevels are high and when most of a forager's time is spent handling seeds rather than searching for more seeds. Additionally,our field study showed that the seed encounter rate of G. allenbyiwas higher than that of G. pyramidum. This difference may giveG. allenbyi an advantage when resource levels are low and whensearching occupies most of the forager's time. The differentadvantages that each species has over the other, under differentconditions, may well be factors promoting their coexistenceover a wide range of resource densities.     

Scent marking by voles in response to predation risk: a field-laboratory validation

Predators use scent to locate their prey, and prey animals oftenalter their behavior in response to predation risk. I testedthe hypothesis that voles would decrease their frequency ofscent marking in response to predation risk. I conducted trialsin which prairie voles, Microtus ochrogaster, and woodland voles,M. pinetorum, were allowed to scent mark ceramic tiles placedin their runways in the field. The tiles were subjected to oneof three treatments: scented with odor from mink, Mustela vison(a rodent predator); rabbit, Oryctolagus cuniculus (a nonpredatormammal control); and no odor (control). No significant differenceswere found in the frequency of scent marking in response tothe three treatments for either species. To validate that volesdid not decrease their scent marking in response to predationrisk, I brought male prairie voles from the field site intothe laboratory and allowed them to scent mark white paper substratetreated with mink odor, rabbit odor, or no odor. No significantdifferences were found in the frequency of scent marks in responseto the three treatments. These results differ from what waspredicted based on laboratory studies with other species ofrodents that show avoidance, reproductive suppression, decreasedactivity, and reduced scent marking in response to odors ofpredators. Voles appear to scent mark different substrates andunder a wide variety of social and environmental situations,and this is not influenced by the presence of odor from a predator.     

The Effect of Accelerated Aging of Sorghum Seeds on Seedling Vigour

Six different levels of vigour of sorghum seeds from an identicallot were obtained through accelerated aging for various periodsof time. Vigour was estimated according to yielding abilityof the seed in the field. After 6 d of aging, seed invigoration,to the extent of a 20% increase in yield, was observed. However,this was followed by a gradual decrease in yield following agingof up to 48 d. All seed lots showed 88–92% germinationor emergence capacity when tested in the laboratory, which correlatespoorly with vigour. However, vigour correlated well with therates of germination and root emergence when tested in the laboratory,as well as with emergence rate in the field.     

Patterns of Growth and Soil-water Utilization in some Exotic Annuals and Native Perennial Bunchgrasses of California

In western California, exotic cool-season annuals appear tohave widely replaced native perennial bunchgrasses as the herbaceouscommunity dominants in grasslands, oak savannas, and oak woodlands.We argue that because these two herbaceous plant types possessvery different life histories, this invasion may have correspondinglyaltered seasonal patterns of soil-water availability. To beginto assess this hypothesis, in this study we compared exoticcool-season annuals and native perennial bunchgrasses in termsof growth, biomass allocation, rooting distribution, root morphology,and soil-water utilization. Exotic cool-season annuals completed their life cycle earlyin the dry season through rapid growth apparently made possibleby a high proportional allocation to shoots in combination withthe efficient production of roots of high specific root length.Further, annuals tended to concentrate root growth and soil-waterutilization in the upper soil profile. In contrast, native perennialbunchgrasses allocated a high proportion of their biomass tothe production of a deep root system, which allowed them tocontinue soil-water utilization well into the dry season andcontribute to the formation of a very dry soil profile. Takentogether, these contrasting patterns suggest that the invasionof exotic cool-season annuals might have produced a correspondingincrease in the amount of water present at depth in the soilprofile during the dry season. Brachypodium distachyon ; Bromus diandrus ; Cynosurus echinatus ; Elymus glaucus ;Nassella pulchra ; Trifolium hirtum ; soil-water utilization; specific root length; growth analysis; rooting depth     

Instar-specific mortalities of coexisting Daphnia species in relation to food and invertebrate predation

Instar-specific mortalities of Daphnia hyalina and D.cucullatawere studied from May 19 to September 29, 1988 in combinationwith invertebrate predator and phytoplankton abundance. Simultaneouslife-table experiments were conducted under semi-natural conditionsin the laboratory to estimate juvenile mortality in a predator-freeenvironment. Juvenile mortality by predation was calculatedas the difference between juvenile mortality in the field andin the experiments and was the most important factor for thedifferences in abundance of the two species. For D.hyalina juvenilemortality was higher in early summer and probably caused byselective predation by Chaoborus flavicans. Predation by Leptodorakindtii was probably more important during the rest of the summer.Estimated mortality by predation adequately explained juvenilemortality, except for a 3-week period in August. Decreasingflagellate densities in July were accompanied by increased juvenilemortalities of D.hyalina and D.cucullata in the life-table experimentsin August and coincided with a Daphnia population decrease.     

Radial Dispersion of Neighbors and the Small-Scale Competitive Impact of Two Annual Grasses on a Native Perennial Grass

In California's Mediterranean type grasslands, native perennial grasses such as Nassella pulchra are surrounded by introduced annual species and these annuals are thought to have displaced natives through much of their range. Amongst other invaders, two grasses Lolium multiflorum and Bromus hordeaceus, commonly dominate portions of the grassland with potential for N. pulchra restoration. We hypothesized that competitor species differences and small‐scale gaps (150 cm²) could be important determinants of N. pulchra survival and performance on these sites. Lolium multiflorum and B. hordeaceus were planted in 20 cm diameter circular plots at a constant rate of 1 seed per cm² surrounding newly transplanted N. pulchra plants. Nassella pulchra showed no significant effect of the species of competitor or from the distribution of the competitors. Both interspersion of patches of bare ground and separation of competitors into patches did not increase N. pulchra pre‐dawn water potential, basal area change, number of seeds produced, or average weight of seeds. The presence of L. multiflorum was associated with a decrease in N. pulchra survival compared with plots with only B. hordeaceus. Plants with increases in basal area of less than 0.75 cm² during the growing season had 74% mortality compared with no mortality in plants with more growth. However, initial N. pulchra plant size was not a good predictor of mortality. Limiting competition from annuals may increase survival of N. pulchra plantings, but 60% of the plants survived for at least 1 year, despite being transplanted into soil containing substantial annual grass seed.     

Differential physiological responses of two congeneric scleractinian corals to mineral accretion and an electric field

Despite increasing popularity of ‘electric’ reefs as a means for reef restoration, there is a distinct lack of quantitative evidence supporting the alleged benefits of this method. This study investigated the effects of an electric field versus an electric field in combination with a cathode on coral growth (skeletal extension) rates, coral survival, zooxanthella densities, chlorophyll a (chl a) concentrations, and chlorophyll fluorescence of Acropora pulchra and A. yongei. Coral transplants were grown for 4 months under three treatment conditions: (1) on an iron cathode, (2) on bamboo inside an electric field, or (3) on bamboo in the absence of an electric field. Contrary to predictions, coral growth rates of both species were highest inside the electric field and not on the cathode. Except for chl a concentrations, the cathode had a significant adverse effect on all measured variables for A. yongei but not for A. pulchra. Treatment had no effect on the survival of A. pulchra, while mortality rates of A. yongei were significantly higher in the presence of mineral accretion compared to the electric field and control. A. yongei on the cathode featured low zooxanthella densities, depressed electron transport rates (rETR) and maximum quantum yield (F _v/F _m), and reduced growth. By contrast, treatment had no effect on the fluorescence characteristics of A. pulchra, and zooxanthella densities were highest for corals on the cathode, coincident with high growth rates relative to the control. Overall, the data indicate that the proposed benefits of the mineral accretion technology to meet important objectives of reef rehabilitation with regard to colony growth and survival should be considered with caution.