The alien grass, Pennisetum setaceum, dominates many of the lowland arid regions that once supported native Heteropogon contortus grassland on the island of Hawaii. Response to drought in a glasshouse was compared between these C4 grasses to test if success as an invader is related to drought tolerance or plasticity for traits that confer drought tolerance. Pennisetum produced 51% more total biomass, allocated 49% more biomass to leaves, and had higher net photosynthetic rates (Pn) on a leaf area basis than Heteropogon. Plants of both species under drought produced less total biomass and increased their allocation to roots compared to well-watered plants, but there was no difference between the two species in the magnitude of these responses. The decline in Pn with decreasing leaf water potential (1) was greater for Pennisetum compared to Heteropogon. Plasticity in the response of Pn to 1, osmotic potentials, and the water potentials at turgor loss in response to drought were not different between the two species. Stomata were more responsive to w in Heteropogon than in Pennisetum and for well-watered plants compared to droughted plants. Plasticity for the stomatal response to w, however, was not different between the species. There was no evidence that the alien, Pennisetum, had greater plasticity for traits related to drought tolerance compared to the native, Heteropogon. Higher Pn and greater biomass allocation to leaves resulted in greater growth for Pennisetum compared to Heteropogon and may explain the success of Pennisetum as an invader of lowland arid zones on Hawaii. 相似文献
A whole-plant carbon balance model incorporating a light acclimation response was developed for Alocasia macrorrhiza based on empirical data and the current understanding of light acclimation in this species. The model was used to predict the relative growth rate (RGR) for plants that acclimated to photon flux density (PFD) by changing their leaf type, and for plants that produced only sun or shade leaves regardless of PFD. The predicted RGR was substantially higher for plants with shade leaves than for those with sun leaves at low PFD. However, the predicted RGR was not higher, and in fact was slightly lower, for plants with sun leaves than for those with shade leaves at high PFD. The decreased leaf area ratios (LARs) of the plants with sun leaves counteracted their higher photosynthetic capacities per unit leaf area (Amax). The model was manipulated by changing parameters to examine the sensitivity of RGR to variation in single factors. Overall, RGR was most sensitive to LAR and showed relatively little sensitivity to variation in Amax or maintenance respiration. Similarly, RGR was relatively insensitive to increases in leaf life-span beyond those observed. Respiration affected RGR only at low PFD, whereas Amax was moderately important only at high PFD. 相似文献
1. 1. Isolated cardiac myocytes of perch, Perca fluviatilis, were kept in culture conditions for 1–2 months at 12 or 22°C. In the culture most myocytes flattened, lost their spindle-shaped morphology, protruded pseudopod-like branches and many of them started visible contractions in 1–2 weeks and continued beating for several months. Myocytes did not divide in the sparse cell population used. Typical intracellular structures could be seen in electron micrographs still after 1–2 months, but the sarcoplasmic organization became gradually more irregular in the culture.
2. 2. Beat rates showed linear temperature relationship on the Arrhenius plot. Myocytes cultivated at 22°C showed higher frequencies and slightly less dependence on temperature than myocytes cultivated at 12°C (apparent activation energies (Ea) 86 and 107 kJ/mol, respectively).
3. 3. Temperature dependence of frequencies was related to the presence of added serum or adrenergic agonists: β-adrenergic agonists increased the frequencies and rendered the cells less dependent on temperature; apparent activation energy was 43 kJ/mol for isoprenaline or adrenaline and 108 kJ/mol for noradrenaline and control group.
4. 4. Heat tolerance was greater in myocytes cultivated at 22°C than in myocytes cultivated at 12°C, and the change in tolerance appeared in 12 h after the alteration of culture temperature and the increased tolerance was persistent after that.
5. 5. It is suggested, that the processes of quick heat-hardening and of slower but persistent heat resistance acclimation developed in these cells in culture conditions but not the capacity acclimation, which seems to be dependent on adrenergic regulation of beat rate.
The effects of rearing and acclimation on the response of adultDrosophila to temperature were investigated in a gradient.D. melanogaster flies preferred a higher mean temperature and were distributed over a wider range of temperatures thanD. simulans flies. Acclimating adults at different temperatures for a week did not influence the response of either species. Adults reared at 28°C as immatures had a lower mean preference than those reared at cooler temperatures, suggesting that flies compensated for the effects of rearing conditions. Adults from tropical and temperate populations ofD. melanogaster andD. simulans did not differ in the mean temperature they preferred in a gradient, suggesting little genetic divergence for this trait within species. The species differences and environmental responses may be related to changes in optimal physiological conditions for the flies. 相似文献
The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine (Pinus taeda L.) seedlings grown in two atmospheric CO2 partial pressures (35 and 65 Pa) and three nutrient treatments (low N, low P, and high N and P). Measurements taken in late autumn (November) after 2 years of CO2 enrichment and nutrient addition showed that photosynthetic rates were higher for plants grown at elevated CO2 only when they received supplemental N. Total rubisco activity and rubisco content decreased at elevated CO2, but there was an increase in activation state. At elevated CO2, proportionately less N was found in rubisco and more N was found in the light reaction components. These results demonstrate acclimation of photosynthetic processes to elevated CO2 through reallocation of N. Loblolly pine grown in nutrient conditions similar to native soils (low N availability) had lower needle N and chlorophyll content, lower total rubisco activity and content, and lower photosynthetic rates than plants grown at high N and P. This suggests that the magnitude of the photosynthetic response to a future, high-CO2 environment will be dependent on soil fertility in the system. 相似文献
In order to identify genes involved in cold acclimation, we have constructed a cDNA library from Brassica napus (cv. Samouraï) cold-acclimated etiolated seedlings. By differential screening, a cDNA clone named pBnC24 (Brassica napus Cold), corresponding to a new cold-inducible plant gene, was isolated. Northern blot hybridizations using total RNA from acclimated and unacclimated seedlings confirmed that BnC24 represents a cold-regulated gene. In contrast with a number of cold-inducible plant genes, BnC24 does not seem to be responsive to abscisic acid (ABA). In addition, further screening of the cold-acclimated cDNA library using pBnC24 cDNA as a probe, allowed the isolation of a second type of homologous cDNA. Sequence analysis showed that the two BnC24 genes encode basic 24 kDa proteins, which are highly hydrophilic and rich in alanine, lysine and arginine. The nucleotide and deduced amino acid sequences of these clones do not show any homology with other previously described cold-induced plants genes. However they have strong homology with a recently discovered human tumour gene, bbc1 (breast basic conserved), which seems to be highly conserved in eukaryotes. 相似文献