Differences in the growth cycle of Ruppia cirrhosa (Petagna) Grande in a Mediterranean shallow system

Ruppia cirrhosa growth cycle was analysed in a southern Mediterranean shallow system throughout 1 year. We examined the temporal variation in R. cirrhosa cover percentage, shoot density, biomass, leaf length, no. flowers m^? 2 and no. fruits m^? 2 in two groups of pond characterized by differences in some environmental parameters. Ponds were comparable for salinity and temperature but they differed for other environmental parameters such as water depth, level of suspended organic matter and chlorophyll a (CHL a). Biological parameter values were higher in B ponds, characterized by lower values of water depth, suspended organic matter and CHL a. A seasonal trend for all considered biological parameters in both typologies of ponds with maximum values in summer was also observed. Moreover, differences were observed between the two groups of ponds in relation to the reproductive strategy adopted by the plant, with populations subjected to a higher organic input and a lower water depth displaying an annual cycle. Results showed how R. cirrhosa is able to resist and to adapt to variations in environmental conditions because of the plasticity and flexibility in the growth cycle and in the reproductive effort.     

Effect of nutrients on decomposition of Ruppia cirrhosa in a shallow coastal lagoon

Hydrobiologia - Here we study the pattern of disappearance of Ruppia cirrhosa Petagna (Grande) litter in the field and evaluate several variables that determine the loss rate: external nitrogen and...     

Measuring water potential (activity) from free water to oven dryness

Water activities (potentials) in plant materials were measured over the range from free water to oven dryness with a Spanner thermocouple psychrometer. In a two-step procedure, water was first condensed on the thermocouple junction for several minutes. The sample was then inserted under the wet thermocouple and the maximum psychrometric cooling was measured in about 10 seconds. Calibration was with saturated salt slurries of known water activities. Psychrometric cooling was a nearly linear function of the water activity and of the negative log of the water potential. The psychrometric cooling to water activity relationship agreed with wetbulb temperature depression to relative humidity relationships given in tables. Water activities of wheat grains and leaves decreased sharply in a curvilinear fashion as their water contents decreased. Some problems of the procedure are discussed.     

Reproductive potential of overwintering, F1, and F2 female boll weevils (Coleoptera: Curculionidae) in the Lower Rio Grande Valley of Texas

The feeding and oviposition activity of overwintering boll weevils, Anthonomus grandis grandis (Boheman), and seasonal fluctuations in development, survival, and reproduction of progeny of overwintering and first- and second-generation boll weevil females were determined in the laboratory at 27 degrees C, 65% RH, and a photoperiod of 12:12 (L:D) h. During the cotton-free period in the Lower Rio Grande Valley, female boll weevils without access to cotton resorb their unlaid eggs and enter reproductive diapause. However, when they were provided daily with greenhouse-grown cotton squares, commencement of oviposition began after 7, 15, or 20 d, depending on when they were captured. Females captured later in the winter fed longer before laying eggs than those captured in the early fall, suggesting that it may take females longer to terminate diapause the longer they have been dormant. The rate of feeding by females was significantly less during the winter months, and this may have affected the rate of diet-mediated termination of dormancy. Females of the first and second generations after the overwintering generation produced a significantly higher percentage of progeny surviving to adulthood and a higher proportion of these progeny were females. Offspring development time from overwintering female parents was significantly longer than that from first and second generations under the same laboratory conditions. The total number of lifetime eggs produced by females of the second generation during the cotton-growing season were approximately 9.9-fold higher than for overwintering females and 1.5-fold higher than for first-generation females. Life table calculations indicated that the population of second-generation boll weevils increased an average of 1.5-fold higher each generation than for females of the first generation and 22.6-fold higher than for overwintering females. Our data showed variation in boll weevil survival, development, and reproductive potential among the overwintering and first- and second-generation females, suggesting inherent seasonal fluctuations in these parameters.     

Hole-drilling in crustaceans by Eledone cirrhosa (Mollusca: Cephalopoda)

Eledone drills holes in the carapace of crustaceans with the tooth-covered salivary complex in conjunction with salivary secretions.     

Reproductive response of Tatera leucogaster (Rodentia) to supplemental food and 6-methoxybenzoxazolinone in Zimbabwe

The effects of 6-methoxybenzoxazolinone (6-MBOA) and supplemental food on the reproductive activity of Tatera leucogaster were examined using a field experiment. The experiment was carried out during the dry season when no pregnancies were observed. Animals provided with 6-MBOA-treated millet seeds for 10 days were not significantly different from animals provided with sham-treated seeds. Supplemental food appeared to have no effect on female reproductive activity, but increased the body mass of both sexes and also the mass of the testes and seminal vesicles. These results provide no evidence for an effect of 6-MBOA on reproductive activity of this equatorial rodent, but supplemental food may promote the maturation and recrudescence of reproductive organs in males.     

Leptodictya tabida (Hemiptera: Tingidae): a potential threat to sugarcane production in Lower Rio Grande Valley of Texas

Areawide surveys and replicated cultivar trials were conducted in 2001 and 2002 in sugarcane (Saccharum spp.) fields in the Lower Rio Grande Valley of Texas to assess the distribution and incidence of the sugarcane tingid Leptodictya tabida (Herrich-Schaeffer). L. tabida was found in all fields surveyed during both years, infesting 60 and 68% of the plants, respectively. The average percentage of leaves infested was 11% in 2001 and 15% in 2002. In 2001, 'CP70-1133' was the most infested, 'CP72-1210' was the least infested, and intermediate infestation levels were evident in 'CP70-321' and 'TCP87-3388'. In 2002, however, TCP87-3388 and CP70-321 were more heavily infested, and CP71-1240 and CP71-1405 were the least infested. Mean densities of L. tabida recovered per plant varied between 1.2 bugs on CP72-1210 and 5.1 on CP70-1133 in 2001, and in 2002, from zero bugs on CP71-1240 and CP71-1405 to 5.3 on CP72-1210. In the cultivar trials, cultivar differences also were evident in both plant and leaf infestation levels, and the proportion of immatures to total L. tabida populations; 'HoCP91-555' had the lowest L. tabida infestations and 'NCo-310' had the greatest levels in both years. Although >5000 L. tabida from the field were collected and kept in the laboratory, no parasitoids were found. The distribution of the infestations during the surveys and in the field trial evaluations suggested that L. tabida populations have been spreading in sugarcane across the Lower Rio Grande Valley. Potential varietal resistance mechanisms are discussed.     

Nodule gas exchange and water potential response to rapid imposition of water deficit

The permeability (P) of the gaseous diffusion barrier in the nodules of soybean [Glycine max (L.) Merr.] decreases when water deficits are extended over a 7 to 10 d period. The mechanism controlling P changes is unclear, but may result from the release of water to intercellular pathways, and an associated change in the nodule water potential. The purpose of these experiments was to impose water deficit treatments rapidly in order to determine the early sequence of the responses of nodule water potential and nodule gas exchange without the complications that arise from long-term water deficit treatments. A vertical, split-root system was used to separate nodule drying effects from plant water deficits by replacing humidified air that was passed over upper root nodules in well-watered plants with dry air, or by replacing the nutrient solution that surrounded lower roots with -1.0 MPa polyethylene glycol (PEG) solution, or by a combination of the dry air and PEG treatments. The PEG treatment caused large decreases in both the components of nodule water potential and nodule relative water content, but there was no indication that these factors had immediate, direct effects on either nitrogenase activity or P. After 7 h of the PEG treatment a significant decrease in nitrogenase activity was found but no decrease in P was detected. These results indicate that changes in nitrogenase activity in response to water deficits precede decreases in P. Exposure of nodules to dry air in well-watered plants had no significant effect on either nitrogenase activity or P during the 7 h treatment.     

The cardiac innervation of Eledone cirrhosa (Lamarck) (Mollusca: Cephalopoda)

The innervation to the cardiac organs and vessels of the octopods Eledone cirrhosa, E. moschata and Octopus vulgaris is described from vitally stained fresh material and wax-embedded sections. This innervation arises from the paired visceral nerves and includes two main peripheral ganglia (fusiform and cardiac) on each side. Several new details of the innervation are reported. Nerves supplying the lateral venae cavae arise from the ventricular nerves at the level of the ventricle. Nerve fibres run to the efferent branchial vessels from the cardiac ganglia. A small ganglion, lying on the auriculo-ventricular nerve, is described for some specimens of both species of Eledone, and is named the auricular ganglion. Commissural strands linking the right and left ventricular nerves of either side are found in Eledone, comparable to those previously described from Octopus. The detailed branching pattern of the innervation shows considerable individual variation and consistent interspecific differences. In E. cirrhosa the fine fibres innervating the inner and outer muscle layers of the auricle show distinct differences in their configuration. Innervation at the surface of the ventricular lumen and around the coronary arterial vessels shows evidence of specialization. The muscle of the branchial heart, particularly the valve leaflets at the junction of the heart and the lateral vena cava, is abundantly innervated. The observations are discussed in relation to other cephalopods and to their probable physiological significance. It is suggested that they provide evidence for a greater degree of neural influence in the control of the cardiac organs than is usually supposed and that they support the idea that the lateral venae cavae have a significant role in the generation of circulatory pressures.     

Wound healing and the haemocyte response in the skin of the Lesser octopus Eledone cirrhosa (Mollusca: Cephalopoda)

The general structure of the skin of the Lesser octopus, Eledone cirrhosa is described. The component regions and cell types being (1) the epidermis, composed of columnar cells with a border of microvilli on their external surface, mucous cells and secretory cells of an unknown type, abutting a non cellular basal lamina; (2) the dermis, containing the elements of the colour change system, vascular and neural processes and an a cellular matrix.
A sequential, morphological study of wound closure revealed three major mechanisms in the healing response; muscular contraction, a dermal cellular reaction and epidermal migration. The process of wound closure in Eledone is significantly slower than that seen, for example, in teleost fish (30 h rather than 30 min for the initiation of epidermal migration). The significance of these results in relation to the osmotic balance between seawater and the internal milieu of Eledone is discussed, together with their relevance to resistance against infection by pathogens.     

Leaf water potential, stomatal resistance, and photosynthetic response to water stress in peach seedlings

Individual groups of peach (Prunus persica [L.] Batsch) seedlings stressed to −17, −26 and −36 bars recovered to control levels within 1, 3, and 4 days, respectively. Stomatal resistance was significantly correlated with both leaf water potential and net photosynthesis. In seedlings stressed to −52 bars, leaf water potential and stomatal resistance recovered sooner than net photosynthesis, despite recovery of 0₂ evolution at a rate similar to leaf water potential. Therefore, some nonstomatal factor other than reduction in photochemical activity must be responsible for the lag in recovery of CO₂ assimilation following irrigation.     

Reproductive response to suckling manipulation in Spanish goats

One hundred and fifty-six Spanish does were used to evaluate the effect of suckling manipulation on postpartum breeding. Does were divided into four herds dependent upon their kidding dates (range from October to January) and location. All kids were nursed ad libitum for approximately 30 days following birth. Groups were then subdivided, and does with kids were randomly allotted to one of the following treatment groups: 1) continuous suckling (CS), 2) once-daily suckling (ODS) or 3) early weaning (EW). Nonlactating does (NL) which lost a kid or aborted were also evaluated for rebreeding performance. At least one fertile male equipped with a marking harness was placed with each treatment group for estrus detection. After 30 days, ODS kids were returned to their dams. The proportion of does exhibiting estrus within 60 days postpartum was greater for ODS and EW does compared to CS does (P<0.05 and P<0.001, respectively). Postpartum interval to first estrus was shorter (P<0.05) for ODS does than for CS does (41.7 and 48.0 days, respectively). The percentage of does conceiving within 60 days postpartum was 25.0, 44.7, 74.4 and 70.7% for CS, ODS, EW and NL does, respectively. The interval from parturition to conception was shorter (P<0.05) for ODS does (43.6 days) than for CS does (50.4 days). Overall kid production was 1.87 kids/doe/year. These results indicate that reducing the suckling stimulus in Spanish does during the breeding season may result in an earlier return to estrus with a greater percentage of does rebreeding within 60 days postpartum.     

House sparrows (Passer domesticus) increase protein catabolism in response to water restriction

Birds primarily rely on fat for energy during fasting and to fuel energetically demanding activities. Proteins are catabolized supplemental to fat, the function of which in birds remains poorly understood. It has been proposed that birds may increase the catabolism of body protein under dehydrating conditions as a means to maintain water balance, because catabolism of wet protein yields more total metabolic and bound water (0.155·H(2)O(-1)·kJ(-1)) than wet lipids (0.029 g·H(2)O(-1)·kJ(-1)). On the other hand, protein sparing should be important to maintain function of muscles and organs. We used quantitative magnetic resonance body composition analysis and hygrometry to investigate the effect of water restriction on fat and lean mass catabolism during short-term fasting at rest and in response to a metabolic challenge (4-h shivering) in house sparrows (Passer domesticus). Water loss at rest and during shivering was compared with water gains from the catabolism of tissue. At rest, water-restricted birds had significantly greater lean mass loss, higher plasma uric acid concentration, and plasma osmolality than control birds. Endogenous water gains from lean mass catabolism offset losses over the resting period. Water restriction had no effect on lean mass catabolism during shivering, as water gains from fat oxidation appeared sufficient to maintain water balance. These data provide direct evidence supporting the hypothesis that water stress can increase protein catabolism at rest, possibly as a metabolic strategy to offset high rates of evaporative water loss.     

Adaptation versus shock response to polyethylene glycol-induced low water potential in cultured potato cells

We compared long-term adaptation versus short-term or shock response of potato ( Solanum tuberosum ) cells to polyethylene glycol (PEG)-induced low water potential. Potato cells, which were allowed to adapt gradually to a decreasing water potential, were able to grow actively in a medium containing 20% PEG. In contrast, no appreciable gain in dry weight was observed in potato cells shocked by abrupt transfer to the same medium. PEG-adapted cells were also salt-tolerant, as they were able to proliferate in a medium supplemented with 200 m M NaCl. No visible ultrastructural changes of mitochondria or proplastids were observed in adapted cells at values of low water potential (about −2.0 MPa), which caused membrane disruption and appearance of lipid droplets in unadapted cells. ABA cellular content increased 5-fold in PEG-shocked cells but no significant increase was found in PEG-adapted cells. The intracellular content of free proline increased 12.5 times over the basal level in PEG-adapted cells and 6.5 times in PEG-shocked cells. As shown by in vivo protein labeling, shock conditions strongly inhibited protein synthesis, which was completely recovered in PEG-adapted cells. Osmotin, a protein associated with salt adaptation in tobacco, was constitutively expressed at a high level in PEG-adapted cells and accumulated in PEG-shocked cells only three days after the transfer in a medium supplemented with 20% PEG. Proline and osmotin accumulation were coincident with the increase in cellular ABA content in PEG-shocked cells, but not in PEG-adapted cells. These data suggest that this hormone is mainly involved in shock response rather than long-term adaptation.     

Changes in leaf water potential and CAM inSempervivum montanum andSedum album in response to water availability in the field

Summary The short term effects of irrigation on diurnal changes in leaf and titratable acidity were examined both inSempervivum montanum and inSedum album, a facultative CAM plant, in the Spanish Pyrenees. InSemperivivum, leaf responded rapidly to irrigation and, in both the control and irrigated plants, increased during the day and decreased during the night and early morning. By contrast, leaf inSedum responded more slowly to irrigation and showed a decrease during the day and an increase in the period between evening and early morning. Under the conditions of the short-term experiments, changes in acid metabolism were not observed in either species following irrigation. The results suggest that transpirational water loss together with redistribution of water within the plant are more important than the osmotic concentration of malic acid in determining leaf in both species and that daytime water loss is greater inSedum than inSempervivum.The effect of long-term water stress on leaf and acid levels was also assessed in both species over a 3-week period. Both leaf and acidification inSempervivum decreased over this time period but could, at least partially, be reversed by irrigation. InSedum, leaf also declined but a more gradual reduction in acidification occurred than inSempervivum. Irrigation inSedum at least partially reversed the decline in leaf but produced a complex pattern of acid metabolism. Nocturnal acidification in the irrigated plants was lower than in the non-irrigated control when preceded by a cool day but showed complete recovery following a hot day. It is suggested inSedum album that C₃ photosynthesis during the preceding light period, as determined by light intensity and leaf temperature, may be important in determining the extent of nocturnal acidification under field conditions.     

Growth and physiological characteristics of Fritillaria cirrhosa in response to high irradiance and shade in age-related growth phases

Fritillaria cirrhosa is a perennial and protected species (grade 3) inhabiting the Chuanxi altiplano of China. Unfortunately, large-scale introduction has not been successful. We hypothesized that excess irradiance is a key factor limiting its introduction, especially young phases. The current study compared responses to irradiance and shade in three age-related growth phases to determine whether shading was the primary limiting factor in cultivation. Polypropylene shading nets were used to mimic a natural shading rate under Rhododendron litangense boscages, the primary community type of F. cirrhosa. Growth and physiological characteristics were investigated. Results showed that shade could increase net assimilation of all phases significantly (p < 0.01). The net increased assimilation in YP (YiPiye, two years old) was mainly due to decreasing VPD (vapor pressure deficit) and increasing g_s (stomatal conductance). Net increased assimilation in SE (SuErzi, three years old) and DL (DengLonghua, four years old) resulted primarily from decreasing VPD and increasing WUE (water use efficiency). However, shade was not the only limiting factor for introduction. We also examined the importance of canopies to F. cirrhosa growth. Maximum photochemical efficiency (Fv/Fm) and non-photochemical quenching (qN) did not differ markedly in DL (p > 0.05), either in full light or under a shading net, which indicated that DL could grow well without canopies. Significant differences were observed (p < 0.01) in Fv/Fm of YP and SE; both values were lower than 0.80 in open sites. YP and SE only weakly subsisted without a canopy. This experiment provides original observations on the quantitative responses to irradiance and shade, introducing F. cirrhosa life history to a wider audience. Shading increased the rate of survival and the net assimilations of young F. cirrhosa (in the first three phases).     

Modeling seed germination in Melisa officinalis L. in response to temperature and water potential

Seed germination is greatly influenced by both temperature (T) and water potential (ψ) and these factors largely determine germination rate (GR) in the field. Quantitative information about T and ψ effects on seed germination in lemon balm (Melisa officinalis L.) is scarce. The main objective of this study was to quantify seed germination responses of lemon balm to T and ψ, and to determine cardinal temperatures in a laboratory experiment. A segmented model was used to describe the effects of ψ (i.e., T) on GR and other germination parameters. The segmented model estimates were 7.2 °C for base (T _b), 28.9 °C for optimum (T _o), 40.1 °C for ceiling temperature (T _c) and 1.64 physiological days (f _o) (equivalent to a GR_max of 0.610 d^?1 and a thermal time of 35.6 °C days) to reach 50 % maximum germination in the control (0 MPa) treatment (R ² = 0.99, RMSE = 0.005 day^?1). The inherent maximum rate of germination (days) was calculated by the [GR_max = 1/f _o] model. ψ affected cardinal temperatures. From 0 to ?0.76 MPa, when ψ increased, T _b was a constant 7.2 °C to ?0.38 MPa and increased linearly to 20.1 °C as ψ decreased. T _o and f _o increased linearly from 28.9 to 30 °C, and from 1.64 to 5.4 day^?1, respectively as ψ decreased. However, there was no signification difference in T _o as ψ decreased nor did T _c decrease from 40.1 to 35 °C as ψ decreased. T _b, T _c and GR_max were the sole parameters affected by ψ and could be used to characterize differences between ψ treatments with respect to GR at various Ts. Therefore, the segmented model and its parameters can be used in lemon balm germination simulation models.