RESUMEN

Many species of the genus Kalanchoe are important horticultural plants. They have evolved the Crassulacean acid metabolism (CAM) photosynthetic pathway to allow them to be better adapted to dry environments. Despite their importance, it is still debating whether Kalanchoe is monophyletic, and understanding the past diversification of this genus requires a tremendous amount of effort and work being devoted to the studies of morphological and molecular characters of this genus. However, molecular information, plastic sequence data, in particular, reported on Kalanchoe species is scarce, and this has posed a great challenge in trying to interpret the evolutionary history of this genus. In this study, plastomes of the five Kalanchoe species, including Kalanchoe daigremontiana, Kalanchoe delagoensis, Kalanchoe fedtschenkoi, Kalanchoe longiflora, and Kalanchoe pinnata, were sequenced and analyzed. The results indicate that the five plastomes are comparable in size, guanine-cytosine (GC) contents and the number of genes, which also demonstrate an insignificant difference in comparison with other species from the family Crassulaceae. About 224 simple sequence repeats (SSRs) and 144 long repeats were identified in the five plastomes, and most of these are distributed in the inverted repeat regions. In addition, highly divergent regions containing either single nucleotide polymorphism (SNP) or insertion or deletion (InDel) mutations are discovered, which could be potentially used for establishing phylogenetic relationships among members of the Kalanchoe genus in future studies. Furthermore, phylogenetic analyses suggest that Bryophyllum should be placed into one single genus as Kalanchoe. Further genomic analyses also reveal that several genes are undergone positive selection. Among them, 11 genes are involved in important cellular processes, such as cell survival, electron transfer, and may have played indispensable roles in the adaptive evolution of Kalanchoe to dry environments.

RESUMEN

Bryophyllum daigremontianum is a very important traditional medicine and ornamental plant. Although Bryophyllum and Kalanchoe have been supported to form a clade, however, lack of chloroplast genomic severely hinders our understanding the phylogenetic relationships between them. In this study, the complete chloroplast genome of B. daigremontianum is first presented. It is 150,058 bp in length consisted a large single-copy (LSC, 82,164 bp) and a small single-copy (SSC, 17,042bp) separated by a pair of inverted repeats (IR, 25,426 bp) including 86 protein-coding genes, 37 tRNA, and 8 rRNA. Phylogenetic analysis supported that B. daigremontianum was closer to K. tomentosa than other species, which showed that chloroplast genome sequences offer a useful resource for future phylogenetic studies of Kalanchoe and Bryophyllum species.

RESUMEN

Equilibrium sorption of n-alkyl esters (dimethyl suberate, diethyl suberate, diethyl sebacate, dibutyl suberate and dibutyl sebacate) and monodisperse alcohol ethoxylates (diethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol and octaethylene glycol monododecyl ether) between the reconstituted cuticular waxes of Stephanotis floribunda Brongn (Madagascar jasmine) or Hordeum vulgare L (barley) leaves and an external aqueous receptor solution was determined. Logarithms of the wax/receptor partition coefficient (K(wax/rec)) of the n-alkyl esters increased linearly with the number of C-atoms. With alcohol ethoxylates, log K(wax/rec) decreased linearly with the number of ethylene oxide units. For both groups of compounds, K(wax/rec) increased with increasing lipophilicity. The values of K(wax/rec) in Stephanotis wax were between 5 and 16 times higher than in barley wax. It is argued that this difference was due to different chemical composition and crystallinity of the waxes. Mobility of [14C]2,4-dichlorophenoxybutyric acid (2,4-DB) in reconstituted Stephanotis and barley wax was increased by a factor of 2-8 by both n-alkyl esters and alcohol ethoxylates. Effects on the mobility of 2,4-DB were linearly related to the internal concentrations of n-alkyl esters and alcohol ethoxylates in reconstituted Stephanotis or barley wax. At the same internal concentrations the effect of n-alkyl esters on the mobility of 2,4-DB in wax exceeded that of alcohol ethoxylates by between 1 and 2 orders of magnitude. Results are discussed in relation to formulating systemic pesticides.

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RESUMEN

Effects of diethyl suberate (DESU), diethyl sebacate (DES), dibutyl suberate (DBSU), dibutyl sebacate (DBS), and tributyl phosphate (TBP) on diffusion of 14C-2,4-dichlorophenoxy butyric acid (2,4-DB) across cuticular membranes (CM) was studied. Astomatous CM were isolated enzymatically from Stephanotis floribunda Brongn. leaves, and diffusion was measured at 20 degrees C. The alkyl-substituted dicarboxylic acids constitute a homologous series with carbon numbers increasing from C12 to C18. Molecular weights increased only moderately from 230.0 (DESU) to 314.5 (DBS), while partition coefficients varied over orders of magnitude from 92 (DESU), to 1213 (DES), to 15,988 (DBSU), to 210,762 (DBS). All the above compounds turned out to be accelerators as they increased 2,4-DB mobility by up to 40-fold with accelerator concentrations in the CM ranging from only 9.2 to 105 g kg(-1). Efficacy (2,4-DB mobility in the presence/mobility in the absence of accelerators) increased with increasing concentrations of accelerators in CM or in reconstituted cuticular waxes. Plotting efficacy vs accelerator concentration in the CM resulted in straight lines, and their slopes increased in the order DBS (0.14), DBSU (0.31), DES (0.51), and DESU (0.85). Hence, DESU was the most powerful accelerator in this series as it increased 2,4-DB mobility in the CM about 6 times more than DBSU. Waxes constitute the major barrier in plant cuticles, and plots of efficacy vs accelerator concentration in Stephanotis wax were also linear, but compared to CM slopes were steeper by factors of 3.20 (DBS), 2.97 (DBSU), 2.70 (DES), and 1.62 (DESU). TBP was similarly effective as DESU, but plots of efficacy vs concentration were not linear, and curves approached a plateau at 60-80 g kg(-1). These data are discussed with regard to suitability of these accelerators for formulating systemic pesticides.

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RESUMEN

Effects of diethylsuberate (DESU), tributyl phosphate (TBP), and monodisperse ethoxylated alcohols (EAs) on rate constants of penetration (k) of model solutes across astomatous cuticular membranes isolated from Madagascar ivy (Stephanotis floribunda) and pear (Pyrus communis) leaves were studied. Model solutes (selected on the basis of their octanol/water partition coefficients, K(ow)) were iprovalicarb (log K(ow) = 3.18), metribuzin (log K(ow) = 1.60), and methyl glucose (MG) (log K(ow) = -3.0). K(ow) varied by more than 6 orders of magnitude. Accelerators had wax/water partition coefficients (log K(ww)) ranging from 1.75 (DESU) to 4.32 (C(12)E(2)), and their equilibrium concentrations in Stephanotis wax varied from 0 to about 160 g kg(-)(1). Accelerators increase solute mobility in cuticles by increasing fluidity of cutin and waxes. This effect was quantified by plotting log k versus the accelerator concentration in wax. With the lipophilic solutes metribuzin and iprovalicarb, these plots were linear. Slopes of these plots characterize the intrinsic activities of the accelerators, and they decreased in the order DESU (0.029) > TBP (0.015) > EAs (0.01). Using these intrinsic activities, the effects of accelerators on rate constants of penetration can be calculated for any accelerator concentration in wax. For instance, at 50 g kg(-)(1), rate constants for lipophilic solutes increased by factors of 28 (DESU), 5.6 (TBP), and 3.2 (C(12)E(n)()), respectively. Permeability of cuticles for the hydrophilic MG was not increased by DESU, TBP, C(12)E(2), and C(12)E(4), while C(12)E(6) and C(12)E(8) increased it. Small hydrophilic solutes such as MG can access aqueous pores in cuticles, and this pathway is not affected by changes in fluidity of amorphous waxes. After rate constants of penetration of ionic CaCl(2) were compared with those for nonionic MG, it was concluded that 60% of the MG diffused across aqueous pores, while 40% used an alternative pathway. Because the solubility of MG in wax is extremely low, it is unlikely that MG diffused along the lipophilic pathway used by metribuzin and iprovalicarb. This agrees with the observation that DESU and TBP had no effect on rate constants for MG. An alternative pathway of unknown properties is suggested. It is speculated that C(12)E(6) and C(12)E(8) sorbed in cuticles might have generated a polar pathway for MG.

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