Net photosynthesis (Pn) of two ecotypes of redbud (Cercis canadensis L.) was studied following growth under high temperatures and increasing drought. Although mexican redbud [C. canadensis var. mexicana (Rose) M. Hopkins] exhibited greater Pn than eastern redbud (C. canadensis var. canadensis L.), Pn decreased at a similar rate under water deficit stress for both ecotypes. Mexican redbud also had greater instantaneous water use efficiency [net photosynthesis: transpiration (WUE)] than eastern redbud. Differences in both Pn and WUE might have been due to differences in leaf thickness. The optimum temperature for potential photosynthetic capacity (37 °C) was unaffected by irrigation or ecotype. Tissue osmotic potential at full turgor was more negative in eastern redbud, but was unaffected by drought stress in either ecotype. Soluble carbohydrate content was higher in eastern redbud, and in both ecotypes, d-pinitol was the major soluble carbohydrate and was considerably more abundant in the water-stressed plants. Total polyol content (myo-inositol + ononitol + pinitol) was also greater in the water-stressed plants. Both ecotypes were very tolerant of high temperatures and drought.
Jason J. Griffin, Thomas G. Ranney, and D. Mason Pharr
Wayne A. Mackay
Micropropagation studies of several desirable species native to west Texas were initiated to develop clonal propagation systems for ornamental production. Actively growing shoots were collected from mature Texas Madrone and Mexican Redbud trees and successfully cultured on basal medium consisting of WPM salts, MS vitamins, 30g·l-1 sucrose, 0.8% Phytagar supplemented with 2.5 mg·l-1 BA. Shoots were subcultured every 4 weeks on the same medium to obtain sufficient culture material for experiments. Experiments were performed examining inorganic salt formulations, growth regulator materials, and gelling agents to optimize shoot proliferation and rooting.
Anthony S. Aiello and Robert J. Joly
Redbud (Cercis canadensis) is known to be very susceptible to injury by road de-icing salts. The purpose of these experiments was to measure the effects of sodium chloride on net CO2 assimilation (A), conductance (g), transpiration (E), and leaf area expansion (LAE) of hydroponically grown redbud seedlings. Eight week-old seedlings were exposed to 0, 4500, and 9000ppm NaCl in the hydroponic growth solution. A, g, E, and LAE were measured for seven consecutive days during treatment application.
A, g, E, an LAE all decreased with increased salt stress. By the seventh day, growth in NaCl at 4500 and 9000 ppm resulted in reductions in A from that that of the control by 34% and 63%, respectively. For the medium treatment, g and E had decreased by 70% over control rates, and by 85% over control for the high treatment. For the 0, 4500, and 9000ppm treatments, total leaf area increased by 68%, 46% and 28%, respectively, over the seven days of the experiment.
Further experiments will examine the effect of treatments on whole plant transpiration, water potential and osmotic potential and will measure the ability of seedlings to recover from treatments of various duration.
Karsedis Distabanjong and Robert L. Geneve
Somatic embryos from Eastern redbud show a high degree of malformation during development and a low conversion rate to seedlings. This problem is common with somatic embryo systems, especially with legume species. A procedure for multiple shoot formation from somatic embryo explants of Eastern redbud was developed that bypasses the need for germination to recover plantlets. Somatic embryo explants cultured on DKW medium containing benzyladenine (BA) and thidiazuron (TDZ) produced more shoots than either treatment alone. The highest number of shoots (3.3 to 3.4 shoots per explant) was obtained from partially desiccated and wounded explants treated with a combination of 5 or 10 M BA and 0.5 or 1.0 M TDZ for 20 days before being transferred to the same medium without TDZ. The number of shoots formed was increased from 1.5 to 3.2 shoots per explant by cutting through the cotyledonary node prior to culture. In addition, the frequency of explants forming shoots was increased by desiccation of somatic embryo explants to ≈50% moisture and by using somatic embryos with two well-formed cotyledons as explants.
N. Y. Liu, H. Khatamian, and T. A. Fretz
Seed germination was 90–95% for Kentucky coffeetree [Gymnocladus dioicus (L.) C. Koch] after concentrated sulfuric acid treatment for 120 to 150 minutes; 97–98% for honeylocust (Gleditsia triacanthos va. inermis L.) following 60, 90, or 120 minutes concentrated sulfuric acid scarification; and was 67–72% for redbud (Cercis canadensis L.) after 30, 60, or 90 minutes of concentrated sulfuric acid scarification followed by a 60-day stratification period. Scanning electron micrographs of acid-scarified Kentucky coffeetree, honeylocust, and redbud seed indicated that lumens of the macrosclereid cells on the seed surface were exposed after acid treatment, permitting imbibition of water. Boiling water treatment ruptured the macrosclerid layer, while seed treated with liquid N2 had fissures that did not appear to penetrate the macrosclereid layer.
Robert L. Geneve, Sharon T. Kester, and Terriawkia A. Woods
Ethephon and ethylene gas applied to intact Eastern redbud seed induced germination in 44 or 53% of dormant seed. However, endogenous ethylene production was not found to be correlated with the release from dormancy during chilling stratification (5°C). Seeds stratified in the presence of 6000 ppm 2.5-norbomadicne germinated at the same percentage as control seeds. Isolated embryos treated with 100 to 500 μM AOA or 1000 μM silver thiosulfate germinated at a slower rate than control seeds, but the release from dormancy during stratification was unaffected by either ethylene inhibitor. Ethylene evolution, ACC and MACC content remained at a low level throughout stratification. EFE activity was not detectable in hydrated dormant or non-dormant seed. All ethylene parameters measured increased sharply during germination with peak activity correlated with radicle emergence. These data indicated that ethylene production was linked to germination, but unrelated to dormancy release in Eastern redbud seed.
David J. Roberts and Dennis J. Werner
The genus Cercis L. (Fabaceae: Caesalpinoideae: Cercideae), also known as redbud, is a valuable commodity in the North American landscape industry and can be found growing in temperate environments across the globe. Cercis consists of ≈10
Paul R. Fantz and Paul Woody
Alison A. Stoven, Hannah M. Mathers, and Daniel K. Struve
Department of Agriculture. Species used in this study: Acer xfreemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus `Prairifire' (Prairifire crabapple), Quercus rubra L. (Northern red oak)
Genhua Niu, Denise S. Rodriguez, and Mengmeng Gu
., 2005 ; Niu et al., 2007 ). Texas mountain laurel is an evergreen shrub or small tree native to Texas, New Mexico, and northeastern Mexico. Mexican redbud is a native, deciduous small tree. It is heat- and drought-tolerant and thrives in well