Whittaker was one of the leading ecologists of his generation, introducing several ideas to plant community ecology. One approach involved deriving environmental-correlation curves in attempts to determine how the abundance of individual species changed along environmental gradients. These curves have been used extensively in the ecological literature of the last 50 years. However, there has been no examination of whether the methods used were sufficiently rigorous to justify Whittaker’s conclusions, let alone the very widespread use of them by others to draw general conclusions. Whittaker’s curves were based on large amounts of fieldwork. However, the sampling methods used were subjective, and the analyses of the data were often circular. When the curves are compared to the data on which they were based, it can be seen that many of the features that Whittaker claimed to see in his graphs are not supported. Whittaker’s main conclusions may have been correct but his studies do not stand up as pieces of scientific work.
We tested the hypothesis that invasive (IN) species could capture resources more rapidly and efficiently than noninvasive (NIN) species. Two IN alien species, Ageratina adenophora and Chromolaena odorata, and one NIN alien species, Gynura sp. were compared at five irradiances. Photon-saturated photosynthetic rate (Pmax), leaf mass (LMA) and nitrogen content (NA) per unit area, and photosynthetic nitrogen utilization efficiency (PNUE) increased significantly with irradiance. LMA, NA, and PNUE all contributed to the increased Pmax, indicating that both morphological and physiological acclimation were important for the three alien species. Under stronger irradiance, PNUE was improved through changes in N allocation. With the increase of irradiance, the amount of N converted into carboxylation and bioenergetics increased, whereas that allocated to light-harvesting components decreased. The three alien species could adequately acclimate to high irradiance by increasing the ability to utilize and dissipate photon energy and decreasing the efficiency of photon capture. The two IN species survived at 4.5 % irradiance while the NIN species Gynura died, representing their different invasiveness. Ageratina generally exhibited higher respiration rate (RD) and NA. However, distinctly higher Pmax, PNUE, Pmax/RD, or Pmax/LMA were not detected in the two invasive species, nor was lower LMA. Hence the abilities to capture and utilize resources were not always associated with invasiveness of the alien species. and Y. L. Feng, J. F. Wang, W. G. Sang.
We studied the role of the δ, µ, and к opioid receptor (OR)
subtypes in the cardioprotective effect of chronic continuous
normobaric hypoxia (CNH) in the model of acuteanoxia/
reoxygenation of isolated cardiomyocytes. Adaptation of rats to
CNH was performed by their exposure to atmosphere containing
12 % of O2 for 21 days. Anoxia/reoxygenation of cardiomyocytes
isolated from normoxic control rats caused the death of 51 % of
cells and lactate dehydrogenase (LDH) release. Adaptation of rats
to CNH resulted in the anoxia/reoxygenation-induced
cardiomyocyte death of only 38 %, and reduced the LDH release.
Pre-incubation of the cells with either the non-selective OR
blocker naloxone (300 nM/l), the δ OR antagonist TIPP(ψ)
(30 nM/l), the selective δ2 OR antagonist naltriben (1 nM/l) or the
μ OR antagonist CTAP (100 nM/l) for 25 minutes before anoxia
abolished the reduction of cell death and LDH release afforded by
CNH. The antagonist of δ1 OR BNTX (1 nM/l) or the κ OR
antagonist nor-binaltorphimine (3 nM/l) did not influence the
cytoprotective effects of CNH. Taken together, the cytoprotective
effect of CNH is associated with the activation of the δ2 and μ OR
localized on cardiomyocytes.