Responses of the moss Tortula ruralis to desiccation treatments. I. Effects of minimum water content and rates of dehydration and rehydration

1981 ◽  
Vol 59 (12) ◽  
pp. 2698-2706 ◽  
Author(s):  
Mark W. Schonbeck ◽  
J. Derek Bewley
Keyword(s):  
Linear Growth ◽  
Dark Respiration ◽  
Natural Habitat ◽  
Dry Weight ◽  
Linear Growth Rate ◽  
Tissue Water ◽  
Visible Injury ◽  
Gross Photosynthesis ◽  
Tortula Ruralis ◽  
Water Contents

Samples of the moss Tortula ruralis were desiccated either rapidly or slowly to different tissue water contents to determine the limits of desiccation tolerance. Experimental samples were rehydrated rapidly by contact with wet filter paper, and gas exchange, chlorophyll content, electrolyte efflux, and linear growth rate were compared with those of control samples. Drying to 0.30–0.089 g H2O∙g dry weight−1 did not significantly affect the moss. Slow drying to 0.058–0.008 g H2O∙g dry weight−1 caused temporary increases in dark respiration and electrolyte leakage, and a slight inhibition of growth. Rapid drying of the same water contents caused visible injury, reduced total chlorophyll and the ratio of chlorophyll a:b, greatly enhanced electrolyte efflux, and severely inhibited gross photosynthesis and linear growth. The damaging effects of rapid drying could be eliminated either by partial desiccation for 1–3 h before rapid drying, or by placing the dry moss in a 100% relative humidity (RH) atmosphere for 1–5 h before rehydration.Tortula ruralis demonstrated greater drought tolerance than many other bryophytes, algae, seeds, and desert angiosperms, and is clearly capable of surviving any drought which might occur in its natural habitat.

Lichen physiology and air pollution. I. Physiological responses of in situ Parmelia sulcata among air pollution zones within Biel, Switzerland

1990 ◽  
Vol 68 (1) ◽  
pp. 35-42 ◽  
Author(s):  
C. von Arb ◽  
C. Brunold
Keyword(s):  
Air Pollution ◽  
Chlorophyll Content ◽  
Dark Respiration ◽  
Natural Habitat ◽  
Dry Weight ◽  
Long Term Effects ◽  
Parmelia Sulcata ◽  
Gross Photosynthesis ◽  
The City

Parmelia sulcata, a rather pollution resistant lichen species, was collected at 13 locations with different levels of air pollution from its natural habitat in the city and the suburbs of Biel, Switzerland, The growth rate, net and gross photosynthesis, release of C-assimilates, dark respiration, and protein and chlorophyll content were determined. Growth rates differed maximally by a factor of 7 with the lowest rates at fee central and most polluted locations of the city. The chlorophyll content was highest in the center and maximally four times lower at the suburban locations. The protein content, dark respiration, and net and gross photosynthesis did not differ significantly between the 13 locations when based on the dry weight, but the percentage of C-assimilates released by the algal cells was up to 15 times lower in the center. These results are different from previous reports where the transplant technique had been used, indicating that the long term effects of air pollution on the lichen metabolism under natural conditions are not the same. Key words: photosynthesis, C assimilation, growth, chlorophyll, dark respiration.

Responses of the moss Tortula ruralis to desiccation treatments. II. Variations in desiccation tolerance

1981 ◽  
Vol 59 (12) ◽  
pp. 2707-2712 ◽  
Author(s):  
Mark W. Schonbeck ◽  
J. Derek Bewley
Keyword(s):  
Water Content ◽  
Desiccation Tolerance ◽  
Dry Weight ◽  
Severe Damage ◽  
Tissue Water Content ◽  
Tissue Water ◽  
Tortula Ruralis

Variations in the apparent desiccation tolerance of the moss Tortula ruralis were traced to several causes. When the moss was kept continuously hydrated for several days, desiccation tolerance tended to decrease ("dehardening"). Conversely, daily episodes of drying and rehydration induced hardening so that the moss could tolerate rapid drying to a tissue water content of 0.008 g∙g dry weight−1.Different clumps of moss showed very different degrees of desiccation tolerance. The least tolerant samples suffered severe damage after rapid drying, whereas the most tolerant suffered little damage, and did not deharden during 3 days continuous hydration.

scholarly journals PHOTOSYNTHESIS, RESPIRATION, AND CARBON COST OF DEVELOPING RABBITEYE BLUEBERRY FRUIT

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1165g-1166
Author(s):  
Keith Birkhold ◽  
Rebecca Darnell ◽  
Karen Koch
Keyword(s):  
Weight Gain ◽  
Fruit Development ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
Dry Weight ◽  
Total Carbon ◽  
Vaccinium Ashei ◽  
Gross Photosynthesis ◽  
Carbon Cost ◽  
Fruit Photosynthesis

Carbon exchange and content of blueberry (Vaccinium ashei) fruit were measured from anthesis through fruit ripening in order to determine the amount of imported carbon required for fruit development. Net photosynthesis occurred in blueberry fruit from petal fall through color break. During this time, gross photosynthesis of fruit decreased from 30.1 μmol CO2·g fw-1·hr-1 to 4.8 μmol CO2·g fw-1·hr-1, and dark respiration decreased from 14.3 μmol CO2·g fw-1·hr-1 to 4.6 μmol CO2·g fw-1·hr-1. After color break, the photosynthetic rate fell to zero, and the respiration rate increased to 8.0 μmol CO2·g fw-1·hr-1, before decreasing. Preliminary data suggest that fruit photosynthesis contributes 11% of the total carbon required (dry weight gain + respiratory loss) during fruit development however, it supplies 50% of the total carbon required during the first 5 days after petal fall. This contribution of carbon from fruit photosynthesis may be critical in initial fruit development since the current season's vegetative growth is not yet providing carbohydrates.

Seasonal changes in the freezing tolerance of the intertidal pulmonate gastropod Melampus bidentatus Say

1985 ◽  
Vol 63 (9) ◽  
pp. 2021-2025 ◽  
Author(s):  
Stephen H. Loomis
Keyword(s):  
Freezing Tolerance ◽  
Dry Weight ◽  
Fresh Weight ◽  
Supercooling Point ◽  
Tissue Water ◽  
Lethal Temperatures ◽  
The Mean ◽  
Pulmonate Gastropod ◽  
Water Contents ◽  
Melampus Bidentatus

The mean lethal temperature of Melampus bidentatus Say ranged from −5 °C in July to −13 °C in December. The percentage of tissue water frozen measured at the mean lethal temperatures was 3% for snails collected in the summer and 74.9% for snails collected in the winter. The supercooling point of the whole snails ranged from −9 °C in September to −6.4 °C in February. The presence of an ice nucleator is indicated by an increase in the supercooling point of the haemolymph from −11.5 °C in the fall to −7.5 °C in the winter. Water content in the snails varied from 2.6 mg water/mg dry weight to 3.6 mg water/mg dry weight; however, there was no correlation between low water contents and an increase in freezing tolerance. Whole animal glycerol contents ranged from 1.14 to 2.96 μmol/g fresh weight and proline contents ranged from 1.20 to 2.19 μmol/g fresh weight. Sorbitol and trehalose were not detected.

Photosynthesis and Respiration of Developing Soybean Pods

1977 ◽  
Vol 4 (5) ◽  
pp. 713 ◽  
Author(s):  
EY Sambo ◽  
J Moorby ◽  
FL Milthorpe
Keyword(s):  
Dark Respiration ◽  
Photochemical Efficiency ◽  
Net Photosynthesis ◽  
Dry Weight ◽  
Daily Basis ◽  
Co2 Uptake ◽  
Response Curves ◽  
Total Import ◽  
Co2 Response ◽  
Gross Photosynthesis

Net CO2 uptake by soybean pods in the light was much less and output in darkness much greater than from equal areas of leaves. The net photosynthesis decreased, becoming negative, and dark respiration increased as seed filling progressed. The photochemical efficiency was the same but the diffusive resistance of pods was about twice and the internal resistance two to three times those of leaves. Fluxes into open deseeded pods were initially much greater than into intact pods but drying out of the tissue soon led to fluxes only about three times greater. From these measurements and light- and CO2-response curves of intact pods, estimates of gross photosynthesis, photorespiration and dark respiration of seeds and hulls were made. These indicated that seed reassimilated slightly more CO2 than they respired when young and about two-thirds thereof at a later stage. Hulls fixed about similar amounts but these were insufficient to prevent net effluxes from pods during the later stages of their development, even at irradiances of 190 W m-2. On a daily basis, direct uptake of CO2 made a negligible contribution to the total import of dry weight by the pod; nevertheless, photosynthesis in the seeds and hulls refixed some 50-70% of the CO2 respired by these tissues.

Rhizosphere competence of benomyl-tolerant mutants of Trichoderma spp.

1988 ◽  
Vol 34 (5) ◽  
pp. 694-696 ◽  
Author(s):  
Jaleed S. Ahmad ◽  
Ralph Baker
Keyword(s):  
Growth Rate ◽  
Carbon Source ◽  
Trichoderma Harzianum ◽  
Sole Carbon Source ◽  
Linear Growth ◽  
Dry Weight ◽  
Linear Growth Rate ◽  
Wild Type ◽  
Trichoderma Spp ◽  
Rhizosphere Competence

Two strains of Trichoderma harzianum and one each of T. koningii, T. polysporum, and T. viride were mutated for tolerance to the fungicide benomyl. Rhizosphere competence index of several mutants of each strain and species was determined by the rhizosphere competence assay. Most of the mutants and not their wild type parents were rhizosphere competent. When the strains and species were grown in Czapek–Dox broth for 6 days with cellulose as sole carbon source, the mutants produced significantly higher dry weight than their parent wild types. Neither the mutants nor the wild types produced biomass in glucose comparable to that in cellulose. Evidence indicates that Trichoderma spp. were induced by mutation to increase their linear growth rate and to become rhizosphere competent. Tolerance to benomyl does not seem to be a necessary attribute of rhizosphere competence.

scholarly journals Relative Humidity Influences Yield, Edible Biomass, and Linear Growth Rate of Sweetpotato

HortScience ◽  
1994 ◽  
Vol 29 (6) ◽  
pp. 609-610 ◽  
Author(s):  
D.G. Mortley ◽  
C.K. Bonsi ◽  
P.A. Loretan ◽  
W.A. Hill ◽  
C.E. Morris
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Ipomoea Batatas ◽  
Linear Growth ◽  
Block Design ◽  
Dry Weight ◽  
Linear Growth Rate ◽  
Storage Root ◽  
Storage Roots ◽  
Temperature Regimes

Growth chamber experiments were conducted to study the physiological and growth response of sweetpotato [Ipomoea batatas (L.) Lam.] to either 50% or 85 % relative humidity (RH). Vine cuttings of T1-155 were grown using the nutrient film technique in a randomized complete-block design with two replications. Temperature regimes of 28/22C were maintained during the light/dark periods with irradiance at canopy level of 600 μmol·m-2·s-1 and a 14/10-hour photoperiod. High RH (85%) increased the number of storage roots per plant and significantly increased storage root fresh and dry weight, but produced lower foliage fresh and dry weight than plants grown at 50% RH. Edible biomass index and linear growth rate (in grams per square meter per day) were significantly higher for plants grown at 85 % than at 50% RH. Leaf photosynthesis and stomatal conductance were higher for plants at 85 % than at 50% RH. Thus, the principal effect of high RH on sweetpotato growth was the production of higher storage root yield, edible biomass, growth rate, and increased photosynthetic and stomatal activity.

scholarly journals PHOTOSYNTHESIS, RESPIRATION, AND CARBON COST OF DEVELOPING RABBITEYE BLUEBERRY FRUIT

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1165G-1166
Author(s):  
Keith Birkhold ◽  
Rebecca Darnell ◽  
Karen Koch
Keyword(s):  
Weight Gain ◽  
Fruit Development ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
Dry Weight ◽  
Total Carbon ◽  
Vaccinium Ashei ◽  
Gross Photosynthesis ◽  
Carbon Cost ◽  
Fruit Photosynthesis

Carbon exchange and content of blueberry (Vaccinium ashei) fruit were measured from anthesis through fruit ripening in order to determine the amount of imported carbon required for fruit development. Net photosynthesis occurred in blueberry fruit from petal fall through color break. During this time, gross photosynthesis of fruit decreased from 30.1 μmol CO2·g fw-1·hr-1 to 4.8 μmol CO2·g fw-1·hr-1, and dark respiration decreased from 14.3 μmol CO2·g fw-1·hr-1 to 4.6 μmol CO2·g fw-1·hr-1. After color break, the photosynthetic rate fell to zero, and the respiration rate increased to 8.0 μmol CO2·g fw-1·hr-1, before decreasing. Preliminary data suggest that fruit photosynthesis contributes 11% of the total carbon required (dry weight gain + respiratory loss) during fruit development however, it supplies 50% of the total carbon required during the first 5 days after petal fall. This contribution of carbon from fruit photosynthesis may be critical in initial fruit development since the current season's vegetative growth is not yet providing carbohydrates.

Effects of developmental status and dehydration rate on characteristics of water and desiccation-sensitivity in recalcitrant seeds of Camellia sinensis

1993 ◽  
Vol 3 (3) ◽  
pp. 155-166 ◽  
Author(s):  
Patricia Berjak ◽  
Christina W. Vertucci ◽  
N. W. Pammenter
Keyword(s):  
Camellia Sinensis ◽  
Developmental Stages ◽  
Scanning Calorimetry ◽  
Tissue Water ◽  
Embryonic Axes ◽  
Freezable Water ◽  
Desiccation Sensitivity ◽  
Accumulation Phase ◽  
Whole Seed ◽  
Water Contents

AbstractThe effect of rate of dehydration was assessed for embryonic axes from mature seeds of Camellia sinensis and the desiccation sensitivity of axes of different developmental stages was estimated using electrolyte leakage. Rapidly (flash) dried excised axes suffered desiccation damage at lower water contents (0.4 g H2O (g DW)−1) than axes dried more slowly in the whole seed (0.9 g H2O (g DW)−1). It is possible that flash drying of isolated axes imposes a stasis on deteriorative reactions that does not occur during slower dehydration. Differential scanning calorimetry (DSC) of the axes indicated that the enthalpy of the melting and the amount of non-freezable water were similar, irrespective of the drying rate.Very immature axes that had completed morphogenesis and histodifferentiation only were more sensitive to desiccation (damage at 0.7 g H2O (g DW)−1) than mature axes or axes that were in the growth and reserve accumulation phase (damage at 0.4 g H2O (g DW)−1). As axes developed from maturity to germination, their threshold desiccation sensitivity increased to a higher level (1.3−1.4 g H2O (g DW)−1). For the very immature axes, enthalpy of the melting of tissue water was much lower, and the level of non-freezable water considerably higher, than for any other developmental stage studied.There were no marked correlations between desiccation sensitivity and thermal properties of water. Desiccation sensitivity appears to be related more to the degree of metabolic activity evidenced by ultrastructural characteristics than to the physical properties of water.

Microborings and growth in Late Ordovician halysitids and other corals

1993 ◽  
Vol 67 (6) ◽  
pp. 922-934 ◽  
Author(s):  
Robert J. Elias ◽  
Dong-Jin Lee
Keyword(s):  
Growth Rate ◽  
Linear Growth ◽  
Inverse Correlation ◽  
Weight Percent ◽  
Late Ordovician ◽  
Coral Growth ◽  
Linear Growth Rate ◽  
Skeletal Density ◽  
Rugose Coral ◽  
Endolithic Algae

Microborings in the Late Ordovician tabulate corals Catenipora rubra (a halysitid) and Manipora amicarum (a cateniform nonhalysitid) and in an epizoic solitary rugose coral differ from nearly all of those previously reported in Paleozoic corals. These microborings were formed within the coralla by endolithic algae and fungi located beneath living polyps. Comparable structures in the Late Ordovician tabulate Quepora ?agglomeratiformis (a halysitid) represent algal microborings, not spicules, and halysitids are corals, not sponges as suggested by Kaźmierczak (1989).Endolithic algae in cateniform tabulates relied primarily on light entering through the outer walls of the ranks rather than through the polyps; lacunae within coralla permitted appropriate levels of light to reach many corallites. The direction of boring was determined by corallum microstructure and possibly also by the distribution of organic matter within the skeleton. There is an apparent inverse correlation between boring activity and coral growth rate.The location and relative abundance of pyritized microborings within calcareous coralla can be established quantitatively and objectively from electron microprobe determinations of weight percent sulfur along appropriate traverses of the coral skeleton. The distribution of such microborings in Catenipora rubra and Manipora amicarum is comparable to algal banding in modern corals; this is the first report of such banding in the interiors of Paleozoic corals. Change in the intensity of boring within each corallum was evidently a response to variation in the linear growth rate of the coral, or to fluctuation in an environmental factor (perhaps light intensity) that could control both algal activity and growth rate in these corals. Change in the algal boring intensity and linear growth rate of the coral was generally but not always seasonal and usually but not invariably associated with change in the density of coral skeletal deposition.Cyclic bands of boring abundance maxima within fossil colonial corals provide a measure of annual linear growth comparable to the widely accepted method based on skeletal density bands. Algal bands are more sporadically developed than density bands within and among coralla, thus increasing the difficulty of interpretation. Fluctuations in the abundance of algal microborings apparently provide a detailed record of changes in the linear growth rate of colonies and of individuals within colonies. Combined analyses of microboring abundance and skeletal density will contribute significantly to our understanding of the biological and environmental factors involved in endolithic activity and coral growth.

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