In situ temperature relationships of biochemical and stomatal controls of photosynthesis in four lowland tropical tree species.

Net photosynthetic carbon uptake of Panamanian lowland tropical forest species is typically optimal at 30-32 °C. The processes responsible for the decrease in photosynthesis at higher temperatures are not fully understood for tropical trees. We determined temperature responses of maximum rates of RuBP-carboxylation (VCMax ) and RuBP-regeneration (JMax ), stomatal conductance (Gs ), and respiration in the light (RLight ) in situ for 4 lowland tropical tree species in Panama. Gs had the lowest temperature optimum (TOpt ), similar to that of net photosynthesis, and photosynthesis became increasingly limited by stomatal conductance as temperature increased. JMax peaked at 34-37 °C and VCMax ~2 °C above that, except in the late-successional species Calophyllum longifolium, in which both peaked at ~33 °C. RLight significantly increased with increasing temperature, but simulations with a photosynthesis model indicated that this had only a small effect on net photosynthesis. We found no evidence for Rubisco-activase limitation of photosynthesis. TOpt of VCMax and JMax fell within the observed in situ leaf temperature range, but our study nonetheless suggests that net photosynthesis of tropical trees is more strongly influenced by the indirect effects of high temperature-for example, through elevated vapour pressure deficit and resulting decreases in stomatal conductance-than by direct temperature effects on photosynthetic biochemistry and respiration.

Cadmium accumulation and tolerance of Lagerstroemia indica and Lagerstroemia fauriei (Lythraceae) seedlings for phytoremediation applications.

Contamination by heavy metals is one of the most serious environmental problems generated from human activities. Because phytoremediation utilizes plants to uptake contaminants, it could potentially be used to remediate metal-contaminated areas. A pot culture experiment with four levels of cadmium (Cd) (0, 20, 40, and 80 mg of Cd/kg dry soil) was conducted to investigate Cd accumulation and tolerance of roots, shoots, and leaves of Lagerstroemia indica and Lagerstroemia fauriei as well as their potential for phytoremediation. Experimental results indicated that Cd inhibited seedling growth only at the higher Cd exposure concentration (40 and 80 mg/kg). The tolerance index revealed that on average L. indica is more tolerant of Cd than L. fauriei. Moreover, plants in the experiment accumulated Cd differentially. In comparisons between L. indica and L. fauriei, the leaves of the former had higher concentrations of Cd, while the roots of latter had higher concentrations of Cd. Furthermore, the roots, shoots, and leaves had very high bioaccumulation factors that markedly exceeded 1.0 (exceptional only in shoots of 80 mg/kg for L. fauriei), indicating that the seedlings extracted Cd from the soil. The leaves' translocation factor of L. indica was greater than 1.0, being significantly higher than that of L. fauriei. Chlorophyll a, Chlorophyll b and total declined in both species significantly as Cd concentrations exceeded 40 mg/kg in the soil. In contrast, lipid peroxidation and proline content was found to increase with increasing Cd concentration. From the assessments of biomass production, Cd tolerance and uptake L. indica and L. fauriei could stand as excellent species for remediating Cd-contaminated soils.

Determination of anthocyanins and exploration of relationship between their composition and petal coloration in crape myrtle (Lagerstroemia hybrid).

Petal coloration and pigment components in 12 American crape myrtle cultivars (Lagerstroemia indicaxLagerstroemia fauriei) and five Chinese crape myrtle cultivars (L. indica hybrids) were studied. Color was measured by CIEL*a*b* scale and anthocyanin composition of crape myrtle was determined using high-performance liquid chromatography coupled to photodiode array detection and electrospray ionization mass spectrometry. The presence of the previously reported delphinidin 3-O-glucoside, petunidin 3-O-glucoside and malvidin 3-O-glucoside were confirmed. Cyanidin 3-O-glucoside was identified in crape myrtle for the first time. We explored the relationship between petal color and anthocyanin contents by multiple linear regression analyses. The results indicated that total flavones and flavonols were important variables and contributed to blue-enhancing in crape myrtle. Based on anthocyanins and co-pigments analysis, flower color breeding in crape myrtle towards true-red and blue were discussed.

In vitro response of encapsulated somatic embryos of Lagerstroemia indica L.

A method to produce encapsulatable units for synthetic seeds was developed in L. indica. Somatic embryos were harvested from leaf derived embryogenic callus on Murashige and Skoog's basal medium supplemented with 2, 4-dichlorophenoxy acetic acid (2, 4-D, 0.5 mg/l), 6-benzyl amino purine (BAP, 1 mg/l) and ascorbic acid (AA, 50 mg/l). The embryos were encapsulated in alginate beads and dehydrated. Germination ability of the artificial seeds were investigated. The frequency of regeneration from the encapsulated embryos was significantly affected by (i) the concentration of alginate (ii) the duration of storage, and (iii) the effect of different types of media. A 2% sodium alginate concentration on MS salts resulted in significantly higher germination frequencies than at other concentrations. L. indica showed maximum germination on MS medium (93.84%) after 6 weeks of culture. The germinated synthetic seeds with well developed roots and shoots were transferred successfully to green house. This is the first report on artificial seeds in Lagerstroemnia indica.

Population Dynamics of Frankliniella bispinosa (Thysanoptera: Thripidae) and the Predator Orius insidiosus (Hemiptera: Anthocoridae) as Influenced by Flower Color of Lagerstroemia (Lythraceae).

Crapemyrtle is a common landscape planting that is a resource subsidy for beneficial insects. Field studies were conducted to determine the influence of crapemyrtle flower color on the population abundances and predator-prey dynamics of the herbivorous Frankliniella species and the predator Orius insidiosus. Adults and immatures of predator and prey were highly anthophilous, preferring white 'Acoma' flowers compared with lavender 'Apalachee', red 'Carolina Beauty', and pink 'Choctaw'. The predator was aggregated with its prey in a density-dependent manner: the adults by preferring the crapemyrtle clones also preferred by the thrips and the nymphs by direct tracking or as a function of increased prey and fecundity. Acoma was best for preference and buildup of O. insidiosus populations, and it was the only clone where there was no buildup in thrips populations. Two species of Karnyothrips (Thysanoptera: Phlaoethripidae), predators of small insects, were common in Tillandsia usneoides, an epiphyte on the crapemyrtle. Crapemyrtle is a bridge to enhance populations of O. insidiosus during summer months when there are few other hosts in the southern USA.