Movement of water from old to young leaves in three species of succulents.
A hypothetical adaptive response of succulent plants to drought-stress is the redistribution of water from old to young leaves. We examined the effects of possible movement of water from old to young leaves in three succulent species, Carpobrotus edulis (weak CAM-inducible), Kalanchoe tubiflora (CAM) and Sedum spectabile (possibly a CAM-cycler or CAM-inducible). Old leaves were removed from plants, and photosynthesis, transpiration, f. wt : d. wt ratios, diurnal acid fluctuations, stomatal conductance and internal CO2 concentrations of the remaining young leaves were measured during drought-stress. Comparison was made with plants retaining old leaves. There was no evidence that water moved from old to young leaves during drought-stress as previously hypothesized. Only in drought-stressed plants of K. tubiflora, were photosynthetic and transpiration rates of young leaves greater on shoots with old leaves removed compared with attached. There was a trend in all species for greater fluctuations in acidity in young leaves on shoots that lacked older leaves. For two of the three species studied, the f. wt : d. wt ratios of young leaves were greater under drought-stress, on shoots with old leaves removed than with them attached. Absence of old leaves may reduce competition for water with young leaves, which consequently have higher water content and greater photosynthetic rates. (+info)
Isolation of angiotensin converting enzyme (ACE) inhibitory flavonoids from Sedum sarmentosum.
Bioassay-guided fractionation of the EtOAc-soluble extract of Sedum sarmentosum afforded a new flavonoid, quercetin-3-O-alpha-(6'''-caffeoylglucosyl-beta-1,2-rhamnoside) (1), along with four known flavonoids, quercetin 3-O-alpha-(6'''-p-coumaroylglucosyl-beta-1,2-rhamnoside) (2), isorhamnetin-3-beta-glucopyranoside (3), quercetin-3-beta-glucopyranoside (4), and kaempferol-3-alpha-arabinopyranoside (5). Purification of these compounds was conducted with the application of various chromatographic methods. Compounds 1-5 inhibited angiotensin I converting enzyme (ACE) activity in a concentration-dependent manner. Compounds 1-5 had 50% inhibitory concentration values of 158.9+/-11.1 microgM, 351.6+/-3.9 microgM, 408.9+/-4.6 microgM, 708.8+/-23.1 microgM, and 392.8+/-13.4 microgM. (+info)
Zinc adsorption and desorption characteristics in root cell wall involving zinc hyperaccumulation in Sedum alfredii Hance.
Radiotracer techniques were employed to characterize (65)Zn adsorption and desorption in root-cell-wall of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) species of Sedum alfredii Hance. The results indicated that at the end of a 30 min short time radioisotope loading period, comparable amounts of (65)Zn were accumulated in the roots of the two ecotypes Sedum alfredii, whereas 2.1-fold more (65)Zn remains in NHE root after 45-min desorption. At the end of 60 min uptake period, no difference of (65)Zn accumulation was observed in undesorbed root-cell-wall of Sedum alfredii. However, 3.0-fold more (65)Zn accumulated in desorbed root-cell-wall of NHE. Zn(2+) binding in root-cell-wall preparations of NHE was greater than that in HE under high Zn(2+) concentration. All these results suggested that root-cell-wall of the two ecotypes Sedum alfredii had the same ability to adsorb Zn(2+), whereas the desorption characteristics were different, and with most of (65)Zn binding on root of HE being available for loading into the xylem, as a result, more (65)Zn was translocated to the shoot. (+info)
Bioactive constituents from Chinese natural medicines. XXII. Absolute structures of new megastigmane glycosides, sedumosides E1, E2, E3, F1, F2, and G, from Sedum sarmentosum (Crassulaceae).
Six new megastigmane glycosides, sedumosides E1, E2, E3, F1, F2, and G, were isolated from the whole plant of Sedum sarmentosum (Crassulaceae). The structures of new constituents including the absolute configuration were elucidated on the basis of chemical and physicochemical evidence. (+info)
Bioactive constituents from Chinese natural medicines. XXIII. Absolute structures of new megastigmane glycosides, sedumosides A(4), A(5), A(6), H, and I, and hepatoprotective megastigmanes from Sedum sarmentosum.
The methanol-eluted fraction of the hot water extract from the whole plant of Sedum sarmentosum (Crassulaceae) was found to show hepatoprotective effect on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes. From the active fraction, five new megastigmane glycosides, sedumosides A(4), A(5), A(6), H, and I, were isolated together with 22 megastigmane constituents. Their absolute stereostructures were elucidated on the basis of chemical and physicochemical evidence. Among them, sedumoside F(1) (IC(50)=47 microM), (3S,5R,6S,9R)-megastigmane-3,9-diol (61 microM), and myrsinionosides A (52 microM) and D (62 microM) were found to show the strong hepatoprotective activity. (+info)
Effects of bacteria on enhanced metal uptake of the Cd/Zn-hyperaccumulating plant, Sedum alfredii.
To investigate the effects of bacteria (Burkholderia cepacia) on metal uptake by the hyperaccumulating plant, Sedum alfredii, a hydroponic experiment with different concentrations of Cd and Zn was conducted. It was found that inoculation of bacteria on S. alfredii significantly enhanced plant growth (up to 110% with Zn treatment), P (up to 56.1% with Cd treatment), and metal uptake (up to 243% and 96.3% with Cd and Zn treatment, respectively) in shoots, tolerance index (up to 134% with Zn added treatment), and better translocation of metals (up to 296% and 135% with Cd and Zn treatment, respectively) from root to shoot. In the ampicillin added treatment with metal addition, stimulation of organic acid production (up to an increase of 133% of tartaric acid with Cd treatment) by roots of S. alfredii was observed. The secretion of organic acids appears to be a functional metal resistance mechanism that chelates the metal ions extracellularly, reducing their uptake and subsequent impacts on root physiological processes. (+info)
Differential generation of hydrogen peroxide upon exposure to zinc and cadmium in the hyperaccumulating plant species (Sedum alfredii Hance).