Plants of F. chiloensis cv. BSP14 (FC) and F. virginiana cv. NCC85-13V (FV) were stressed until wilting, then watered for 2 days prior to measurement. Diurnal measurements of leaf conductance and water relations were conducted. Leaf conductance of stressed FC plants was generally lower, than that of controls at most times, but there wee no difference between the two in FV. Leaf conductance and transpiration rates had not fully recovered to pre-stress levels within this recovery period, Leaf wafer potential declined from predawn to midday, more in stressed than control plants of both species. Leaf osmotic potential averaged 0.4 and 0.2 MPa lower in stressed than control FC and FV plants, respectively, Greater differences occurred at midday than predawn. Leaf pressure potential of stressed plants was higher predawn than midday, 1.4 vs. 0.7 MPa, in FC; it was not different for FV at most times. The difference in water relations between these two species may be explained by a greater residual effect from the osmotic adjustment in FC es compared to FV that occurred during prior water deficit stress.
Effects of a wet tent (cloth continuously wetted), an intermittent mist, and a shade system were examined for establishment, survival, and growth of microcuttings of three cultivars of Euphorbia fulgens Karw. ex Klostch. The wet tent system resulted in high survival rates and rapid plantlet growth. Microcuttings placed in the mist system had survival rates close to that in the wet tent, but had the poorest plantlet growth. Microcuttings placed directly in the shade had a poor survival rate, but plantlets that survived grew as well as those from the wet tent. In all three acclimatization systems, microcuttings of the white cultivar had the highest survival rate; those of the orange and red cultivars were second and third, respectively. No difference was found in plantlet growth among the surviving cultivars after removal from treatment in acclimatization systems. Microcuttings 41 to 50 mm long survived best; survival rate increased with microcutting length. The minimum microcutting length for satisfactory survival rates (79%) was 31 mm. Microcuttings rooted a month earlier than did conventional stem-tip cuttings in the wet-tent system.
Effects of trans-zeatin, sucrose, myo-inositol, and medium pH on shoot proliferation of Euphorbia fulgens Karw. ex Klostch were studied in vitro. Maximum shoot production occurred on media supplemented with 5 μΜ zeatin, but maximum shoot length with 5 to 15 μΜ. Shoot production increased with sucrose concentration, and was maximal at 131.5 mM. myo-lnositol concentration up to 0.6 mM did not have a significant effect on shoot production, but >1.1 mM reduced it. The optimal medium pH was 5.3 for shoot proliferation, but lower pH values stimulated shoot growth. Chemical names used: trans-2-methyl-4-(1H-purin-6-ylamino)-2-buten-l-ol (trans-zea-tin), α-D-glucopyranosyl-β-D-fructofuranoside (sucrose).
Nodal sections of actively growing apical shoots from greenhouse-grown plants of Euphorbia fulgens Karw. ex Klotsch initiated new shoots after 4 weeks on a modified Murashige and Skoog (MS) medium supplemented with 9.1 μm zeatin. When cultures from the initiation stage were transferred for proliferation to the same medium, up to 14 shoots 5 mm long or longer were obtained per culture 4 weeks later. Through subcultures, 40 transplantable shoots per explant could be produced within 12 weeks. Shoots were rooted in vitro in the greenhouse with satisfactory survival rates. Chemical names used: (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buten-1-ol (zeatin).