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1.
CO2 and water vapour exchange in four alpine herbs at two altitudes and under varying light and temperature conditions 总被引:1,自引:0,他引:1
CO2 and water vapour exchange rates of four alpine herbs namely: Rheum emodi, R. moorcroftianum, Megacarpaea polyandra and Rumex nepalensis were studied under field conditions at 3600 m (natural habitat) and 550 m altitudes. The effect of light and temperature on CO2 and water vapour exchange was studied in the plants grown at lower altitude. In R. moorcroftianum and R. nepalensis, the average photosynthesis rates were found to be about three times higher at 550 m as compared to that under their natural habitat. However, in M. polyandra, the CO2 exchange rates were two times higher at 3600 m than at 550 m but in R. emodi, there were virtually no differences at the two altitudes. These results indicate the variations in the CO2 exchange rates are species specific. The change in growth altitude does not affect this process uniformly.The transpiration rates in R. emodi and M. polyandra were found to be very high at 3600 m compared to 550 m and are attributed to overall higher stomatal conductance in plants of these species, grown at higher altitude. The mid-day closure of stomata and therefore, restriction of transpirational losses of water were observed in all the species at 550 m altitude. In addition to the effect of temperature and relative humidity, the data also indicate some endogenous rhythmic control of stomatal conductance.The temperature optima for photosynthesis was close to 30°C in M. polyandra and around 20°C in the rest of the three species. High temperature and high light intensity, as well as low temperature and high light intensity, adversely affect the net rate of photosynthesis in these species.Both light compensation point and dark respiration rate increased with increasing temperature.The effect of light was more prominent on photosynthesis than the effect of temperature, however, on transpiration the effect of temperature was more prominent than the effect of light intensity.No definite trends were found in stomatal conductance with respect to light and temperature. Generally, the stomatal conductance was highest at 20°C.The study reveals that all these species can easily be cultivated at relatively lower altitudes. However, proper agronomical methodology will need to be developed for better yields. 相似文献
2.
Abscisic acid (ABA)-induced increase in stomatal diffusive resistance (SDR) in excised leaves of bean (Phaseolus vulgaris L. cv Pencil Pod) and maize (Zea mays L. cv Golden Bantam) is inhibited by low concentrations of trans-cinnamic acid (TCA) (1 micromolar) and p-coumaric acid (PCA) (10 micromolar) when given together with ABA (10 micromolar) in the transpiration stream through the cut end of the petiole or leaf blade. A concentration effect is observed both in the ABA action and its reversal by phenolic acids. Leaves having attained a high diffusive resistance in ABA solution recover rapidly when transferred to water. ABA (10 micromolar) induced closure of the stomata in onion, Allium cepa L. and Vicia faba epidermal peels. This is associated with loss of K+ from guard cells. In the presence of TCA (10 micromolar) and PCA (10 micromolar) K+ is retained in the guard cells with open stomata. The dark closure of stomata is also inhibited by TCA and PCA. It is suggested that these phenolic acids may inhibit the ABA effect by competing with or acting on some ABA-specific site, probably located on the plasma membrane, regulating flux of K+ ions. A weak association of ABA with the plasma membrane is envisaged because of the rapid recovery obtained upon transferral of the leaves to water. 相似文献
3.
An in vitro procedure for large scale multiplication of Sterculia urens Roxb. (Gum Kadaya Tree) has been developed using cotyledonary node segments. An average of 4.0 shoots per node were obtained on Murashige and Skoog's (MS) medium containing 2.0 mgl–1 6-benzyl amino-purine (BAP) within 21 days of initial culture. Upon subsequent subculture 16 shoots/node could be harvested every three weeks and upto three times. Sixty per cent of the shoots were successfully rooted. Rooted plantlets were transferred to plastic pots containing soil under mist house conditions before they were finally exposed to an external environment. Fifty seven per cent of the plantlets survived in nursery sheds. 相似文献
4.
Application of abscisic acid (ABA) brings about stomatal closure within 30 min in epidermal peels of Vicia faba . A number of phenolic compounds antagonise the effect of ABA. Derivatives of benzoic acid, cinnamic acid, coumarin and flavonoids have been studied in order to establish structure – activity relationship. Derivatives of benzoic acid reverse the ABA effects. Coumarin, esculetin and three hydro derivatives of cinnamic acid fail to show the anti-ABA activity. Thus, the presence of parahydroxyl group and double bond in the side chain is necessary for anti-ABA activity. 相似文献
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Anin vitro procedure for large scale multiplication ofBoswellia serrata Roxb. has been developed using cotyledonary node segments. In average 4 shoots per node were obtained on Murashige and Skoog’s (MS) medium containing 0.5 mg dm?3 6-benzylaminopurine (BAP) and 0.05 mg dm?3 napthaleneacetic acid (NAA) within 22 d. By repeated subculture technique 90–100 shoots per node could be obtained after 88 d of initial culture. Shoots could be rooted on MS medium containing 1/4 salts, 1% saccharose, and a combination of 0.5 mg dm?3 indole-3-butyric acid (IBA) and 0.25 mg dm?3 indole-3-acetic acid (IAA). Addition of antioxidants like polyvinylpyrrolidone (PVP-50 mg dm?3) and ascorbic acid (100 mg dm?3) in both multiplication and rooting media prevented browning of cultures. Approximately 80% of shoots rooted within 8–10 d. Rooted plantlets were kept for 15 d in culture bottles containing SoilriteTM irrigated with a nutrient solution containing 1/4 MS salts and finally transferred to pots containing soil: SoilriteTM (1∶1), mixture with 70% transplantation success. 相似文献
7.
The formation of germtubes by twelve clinical isolates of C. albicans was studied in human serum containing per millilitre 103 to 109 organisms as: Staphylococcus pyegene, Escherichia coli, Klebsiella pneumoniae, Lactobacillus acidophilus and Proteus vulgaris. All the five bacteria inhibited formation of germtubes by C. albicans at all concentrations and the percent germtube formed diminished with increasing concentration of the bacteria. Lactobacillus acidophilus inhibited the formation of germtubes maximally followed by Staphylococcus pyogene, Escherichia coli and Klebsiella pneumoniae. Proteus vulgaris in the concentrations of 103 to 107 bacteria per millilitre produced only insignificant inhibition of formation of germtubes by C. albicans. Since germtubes of C. albicans are invasive, it is suggested that inhibition of blastospo-regermtube transformation may be significantly responsible for prevention of infection by C. albicans by coexisting bacterial flora. 相似文献
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Synthetic GnRH, at a dose of 100 mcg, was injected intravenously into 12 healthy, single, regulary menstruating women in order to test the capacity of the pituitary to release LH and FSH in response to the administration of the decapeptide. A total of 12 tests was performed during different stages of the menstrual cycle, i.e., on D 3-4, D 13-16 and D 21-29 of the cycle. Following GnRH administration, there was a rapid increase in serum levels of LH. Although there was a pronounced variation of responses in the course of the menstrual cycle, the maximum response was observed 30 to 40 min., after injection. The mean net increases of LH (M +/- SE mIU/ml) were in the following order: 118 +/- 22 in the preovulatory phase, 63 +/- 12 in the midluteal phase, and 35 +/- 7 in the early follicular phase. A concomitant but much smaller rise in serum levels of FSH was observed. These data indicate that the sensitivity of pituitary gonadotrophs to GnRH is preferentially increased during the preovulatory phase of the cycle, thus lending further support to already published data which demonstrated increased pituitary sensitivity to GnRH toward midcycle. 相似文献
10.
Pearl A. McElfish Aaron J. Scott Harish E. Chatrathi Brett Rowland Christopher R. Long Nirav Nagarsheth Mikaila Calcagni Jay Patolia Lauren K. Haggard-Duff James P. Selig 《The Yale journal of biology and medicine》2021,94(1):5
Hypertension and type 2 diabetes (T2D) are major public health issues that disproportionately affect minority communities, including Native Hawaiians and Pacific Islanders (NHPI). Minority communities are also more likely to have undiagnosed hypertension and T2D. Marshallese Pacific Islanders have been shown to have high proportions of diagnosed and undiagnosed hypertension and T2D. Using survey and biometric data collected from 378 overweight/obese Marshallese Pacific Islander adults, this study documents the prevalence of hypertension and T2D, as well as the prevalence of undiagnosed hypertension and T2D. The study also examines associations between undiagnosed hypertension and undiagnosed T2D and age group, sex, health care access (defined by foregone care due to cost and health insurance status), and body mass index (BMI). Among participants with blood pressure readings indicative of hypertension, 68.4% were undiagnosed, and among participants with HbA1c indicative of T2D, 31.6% were undiagnosed. A quarter of participants (24.5%) had blood pressure and HbA1c measures indicative of both undiagnosed hypertension and undiagnosed T2D. Undiagnosed hypertension was significantly associated with age group (p’s<0.0001) and sex (p=0.028). Undiagnosed T2D was significantly associated with age group (p’s<0.05), forgone care due to cost (p=0.018), health insurance status (p=0.035), and BMI (p=0.001). Participants in this study had high proportions of undiagnosed hypertension and undiagnosed T2D. These findings will be immediately useful for those working to address hypertension and T2D disparities among Marshallese and other NHPI populations. 相似文献