Influence Of Nutrient Status Research Articles

Influence of nutrient status on the response of the diatom Phaeodactylum tricornutum to oil and dispersant

Phytoplankton play a central role in our ecosystems, they are responsible for nearly 50 percent of the global primary productivity and major drivers of macro-elemental cycles in the ocean. Phytoplankton are constantly subjected to stressors, some natural such as nutrient limitation and some manmade such as oil spills. With increasing oil exploration activities in coastal zones in the Gulf of Mexico and elsewhere, an oil spill during nutrient-limited conditions for phytoplankton growth is highly likely. We performed a multifactorial study exposing the diatom Phaeodactylum tricornutum (UTEX 646) to oil and/or dispersants under nitrogen and silica limitation as well as co-limitation of both nutrients. Our study found that treatments with nitrogen limitation (-N and-N-Si) showed overall lower growth and chlorophyll a, lower photosynthetic antennae size, lower maximum photosynthetic efficiency, lower protein in exopolymeric substance (EPS), but higher connectivity between photosystems compared to non-nitrogen limited treatments (-Si and +N+Si) in almost all the conditions with oil and/or dispersants. However, certain combinations of nutrient limitation and oil and/or dispersant differed from this trend indicating strong interactive effects. When analyzed for significant interactive effects, the-N treatment impact on cellular growth in oil and oil plus dispersant conditions; and oil and oil plus dispersant conditions on cellular growth in-N-Si and-N treatments were found to be significant. Overall, we demonstrate that nitrogen limitation can affect the oil resistant trait of P. tricornutum, and oil with and without dispersants can have interactive effects with nutrient limitation on this diatom.

Influence of nutrient status on the accumulation of biomass and lipid in Nannochloropsis salina and Dunaliella salina

Microalgae have been proposed as carbon-neutral and sustainable fuel feedstock producers due to their fast growth and high lipid content. In this investigation, we examined the effect of different nutrient stresses on overall lipid productivities and physiology, in two microalgae species, namely Nannochloropsis salina and Dunaliella salina. For both the species in semi-continuous cultures, the dilution ratio was found to affect only the harvest period and not the biomass or lipid productivity. Harvest at different growth phases was influenced by the temporal nutrient status of the medium leading to different productivity of biomass and lipids. These two species also showed different cellular biochemistry and lipid metabolism in response to the different nutrient stresses. More efficient stimulators of lipid production than the commonly employed nitrogen limitation were identified, for e.g. deficiency of trace element. Significant influence of nutrient deficiency on lipid profiles was observed in N. salina, such as chain length and degree of unsaturation, with desirable characteristics for biodiesel production. The comparison of lipid profiles between these two species revealed phenomenal differences in some fatty acids, e.g. a higher level of γ-linolenic acid (C18:3n6) in D. salina and the exclusive presence of palmitoleic acid in N. salina. The biochemical composition with respect to the cellular function of the fatty acids is discussed with an attempt to better understand the differences in the lipid profiles.

Influence of nutrient status of soils on mortality of Shisham (Dalbergia sissoo) in semi-arid regions of Haryana

An experiment was conducted to study nutrient status of soils under healthy as well as dead trees of Dalbergia sissoo on six different locations selected in Chaudhary Charan Singh Haryana Agricultural University, Hisar and nearby places with an objective to ascertain whether the mortality is caused by the deficiency of any plant nutrient. Soil samples from six different depth up to 150 cm were collected and analyzed for important nutrient like nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S). Total macronutrient such as N, P, K and available N, P, K, Ca, Mg and S were found higher in the soils under healthy as compared to dead trees and its concentration decreased with the increase in the soil depth at all the six locations. Nutrients were found higher under healthy trees as compared to dead trees and as the depth increased the nutrient concentration were also decreased. It is concluded that in all sites under study the nutrient concentration could not cause mortality in Shisham trees.

Influence of nutrient status and grazing pressure on the fate of Francisella tularensis in lake water

The natural reservoir of Francisella tularensis, the causative agent of tularaemia, is yet to be identified. We investigated the possibility that Francisella persists in natural aquatic ecosystems between outbreaks. It was hypothesized that nutrient-rich environments, with strong protozoan predation, favour the occurrence of the tularaemia bacterium. To investigate the differences in adaptation to aquatic environments of the species and subspecies of Francisella, we screened 23 strains for their ability to survive grazing by the ciliate Tetrahymena pyriformis. All the Francisella strains tested were consumed at a low rate, although significant differences between subspecies were found. The survival and virulence of gfp-labelled F. tularensis ssp. holarctica were then studied in a microcosm experiment using natural lake water, with varying food web complexities and nutrient availabilities. High nutrient conditions in combination with high abundances of nanoflagellates were found to favour F. tularensis ssp. holarctica. The bacterium was observed both free-living and within the cells of a nanoflagellate. Francisella tularensis entered a viable but nonculturable state during the microcosm experiment. When studied over a longer period of time, F. tularensis ssp. holarctica survived in the lake water, but loss of virulence was not prevented by either high nutrient availability or the presence of predators.

Poplar nutrient resorption in fall or drought: influence of nutrient status and clone

Nutrient mobilization in hybrid poplars was studied in two greenhouse experiments. Half the clones in each experiment were drought resistant and half were drought sensitive. In experiment 1, four clones were grown at three levels of N, two levels of P, and with four drought treatments. In experiment 2, six clones received two levels of N and three levels of K. Well-watered trees, trees subjected to drought conditions once, and hardened drought-stressed trees were harvested in late summer, and other well-watered trees were harvested in fall. Mobilization of nutrients differed with speed and intensity of drought. During gradual drought in the first experiment, N and P were resorbed but not K or Cu. In experiment 2, drought was too rapid for resorption. Instead, nutrients became more concentrated: increased N facilitated hardening and osmotic adjustment, while K moved out of the leaves on rewatering. In fall, N, P, Cu, and K were resorbed. Increased K supply increased fall resorption efficiency of Cu, N, and P but not K. Increased N supply improved fall resorption proficiency of K at low levels of supply. However, clonal productivity on dry sites was more related to leaf retention in drought and in fall than to resorption efficiency.

Poplar nutrient resorption in fall or drought: influence of nutrient status and clone

Poplar nutrient resorption in fall or drought: influence of nutrient status and clone

Comparative study of interactions between Bremia lactucae and lettuce cells in suspension culture and in cotyledons

A critical comparison of the relationship between fungal development and irreversible membrane damage (IMD) in lettuce cells penetrated by Bremia lactucae in suspension cultures or in the epidermis of the cotyledon petiole has revealed the following important differences between interactions occurring in vitro and in the plant. (1) Large fungal colonies comprising intercellular hyphae and the formation of numerous haustoria did not develop in suspension cultures. (2) IMD occurred at earlier stages of fungal development in cultured cells than in cotyledons of susceptible cultivars. (3) In resistant cells undergoing the hypersensitive reaction (HR) fungal development was more advanced in vitro than in the plant at the time of IMD. (4) Suppression of the plant's metabolic activity either by heat-shock or blasticidin S (an inhibitor of protein synthesis) had less effect on the HR in cultured cells than in the plant. Despite these differences, B. lactucae did produce characteristic infection structures in cultured cells and, in certain cultivar/isolate interactions e.g. cvs. Diana ( Dm 1 + Dm 3 + Dm 7 + Dm 5/8) and Cobham Green (no known resistance genes) with isolates V0/11 (with at least one dominant avirulence allele at loci A 1, A 3, A 7 and A 5/8) and TV (with no dominant avirulence alleles at loci A 1, A 3, A 7 or A 5/8), the expected compatibility or incompatibility was clearly expressed. By contrast, the expected rapid HR of cells of cv. Valmaine ( Dm 5/8) challenged by isolate V0/11 was not observed in cultured cells. The influence of nutrient status on the responses of cultured lettuce cells is discussed.