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- Author or Editor: Baolin Zhang x
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 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).
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.
A comparative study was performed to elucidate changes in the water relations of Fragaria chiloensis (L.) Duch. `BSP14' (FC) and F. virginiana (L.) Duch. `NCC85-13V' (FV), grown in containers in a greenhouse, in response to imposed water deficit stress and subsequent recovery. At incipient wilting, a reduction in osmotic potential at full turgor (Ψπ 100 of 0.42 MPa occurred in leaves of FC, while no change was found in FV. Leaf water potential (Ψ) isotherms revealed that as leaf Ψ and relative water content (RWC) declined, stressed FC plants maintained a higher turgor potential (ΨP) and lower osmotic potential (Ψπ) than nonstressed (control) plants, while there was no effect of drought stress on these relationships in the FV plants. From the isotherms, turgor loss was estimated to occur at a lower leaf Ψ and RWC in stressed FC plants than either in control FC plants or stressed and control FV plants. During a diurnal phase 36 hours after wilting, leaf Ψ, Ψπ and RWC of the FC selection were generally lower in stressed than in control plants, with differences ranging from 0.14 to 0.74 MPa, 0.28 to 0.47 MPa, and 1% to 8%, respectively. In the FV selection, Ψπ was 0.09 to 0.31 MPa lower in stressed than in control leaves, while the other characteristics were not affected. Leaf ΨP, of stressed FC plants was 0.09 to 0.27 MPa higher than controls during the dark period, but was similar during the day. When plants of both species were grown and stressed in the same container, FV plants wilted ≈4 days earlier than FC plants, and foliar Ψπ 100 of FC was 0.35 MPa lower than that of FV at incipient wilting. The isothermal relationships between leaf Ψ and Ψπ 100 indicated FC had a Ψπ 100 ≈ 0.25 MPa lower than FV at a Ψ <1.5 MPa. This study provided evidence for greater osmotic adjustment in response to imposed water deficit stress in a selection of F. chiloensis than in one of F. virginiana.
The effect of water deficit stress on the foliar solute concentration of Fragaria chiloensis Duch. cv. `BSP14' (FC) and F. virginiana Duch. cv. `NCC85-13V (FV) was studied to assess solute contribution to osmotic adjustment. Plants were stressed for three wilting cycles by withholding water until incipient wilting, followed by a recovery period. The length of each cycle for the FC selection was J-fold that for the FV selection. Wilting of FC plants occurred at a leaf water potential (ψ) 1.1 MPa lower, a leaf osmotic potential (ψπ) 0.45 MPa lower, and a relative water content (RWC) 14% lower than for FV plants. Leaf ψπ at full turgor (ψπ 100) was reduced in the FC selection from 0.11 to 0.27 MPa but not in the FV selection. Water deficit stress increased the total foliar soluble carbohydrate (TSC) concentration from 1.4- to 2.4-fold for FC during each cycle. Glucose and fructose were the primary carbohydrates, comprising >50% of the TSC. Leaf starch concentration decreased appreciably to 4% to 6% of nonstressed (control) levels for FC during each cycle. In the FC selection, the TSC: starch ratio was considerably higher, 30- to 50-fold, in stressed than in control plants. No consistent changes in solute or starch concentration were observed in the FV selection. Total free amino acid concentration increased from 1.8- to 2.7-fold in FC plants in response to stress. Proline accumulation was not detected. The solutes, TSC and amino acids, accounted for <40% of the measured ψπ 100 in control plants, although the average contribution of these solutes to the measured leaf ψπ 100 increased to 40% or more in stressed FC plants. However, the stress-induced increase in solute concentration fully accounted for the reduction of leaf ψπ 100 in the FC selection plants.
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).