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  • Author or Editor: P. C. Andersen x
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Fruit characteristics of Oriental persimmon (Diospyros kaki L.) [`Fuyu' (Expts. 1 and 2) and `Tanenashi' (Expt. 3)] were assessed as a function of five pollination treatments: 1) hand-pollination (HP) with `Gailey' pollen (G); 2) HP with `Nishimura Wase' pollen (NW); 3) HP with `Turkeytown' pollen (T) (not used for `Tanenashi'); 4) open-pollination (OP), which did not necessarily result in pollination; and 5) nonpollination (NP) where pollination was prevented by covering the flower. Final fruit set of `Fuyu' and `Tanenashi' was higher for G and NW pollen than for NP. Differences in fruit set among the remaining treatments depended on the particular experiment. For example, fruit set for OP was higher than for NP in Expts. 1 and 3 but not Expt. 2. Fruit weight and soluble solids concentration (SSC) of `Fuyu' were not affected by treatment in Expts. 1 and 2; however, in Expt. 2, fruit height and diameter of G, NW, T, or OP were larger than for NP. Seed count per fruit was inversely related to fruit development period but did not influence fruit size or SSC. Fruit height, diameter, weight, and total soluble solids of `Tanenashi' for G, NW, and OP exceeded those for NP, although rarely were seeds present.

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Abstract

Net CO2 assimilation rate (A) and plant water relations of peach [Prunus persica (L.) Batsch cv. Flordaking] leaves were monitored during development under field conditions. Leaf conductance to water vapor (gl) and transpiration rate (E) of unfolding and expanding leaves approached maximum values before maximum A values were achieved. Net CO2 assimilation rate and water use efficiency (WUE) were greatest for recently expanded leaves and gradually declined with age after full expansion. Leaf water potential (ψw) was similar for all leaf ages under field conditions. Leaf dry weight/cm2 and chlorophyll/cm2 increased with leaf age after expansion. Diurnal patterns of gl, E, and ψw were similar for expanded spring- and summer-flush leaves. Midday ψw of −2.4 MPa (ψp = about 0.3 MPa) did not reduce gl. Expanding shoots had higher osmotic potentials (ψπ) and thus maintained lower turgor potentials (ψp) than fully expanded shoots. Shoot and leaf elongation rates were related exponentially to ψp and were reduced drastically below ψp 1.0 and 0.7 MPa, respectively. The bulk modulus of elasticity (є) increased linearly with ψp, but there were no significant differences in є of expanding and nonexpanding shoots. As leaf water deficits developed, shoot and leaf expansion were inhibited prior to gl or A. Thus, a moderate level of water stress can reduce the rate of vegetative growth of peach trees without concomitant reductions in carbon assimilation.

Open Access

Abstract

Spring- and summer-flush pecan [Carya illinoensis (Wangenh.) C. Koch] leaves were evaluated to determine climatological factors affecting leaf gas exchange, biophysical factors affecting growth, and to investigate the potential impact of a summer growth flush on alternate bearing. Expanding leaves had a higher osmotic potential, lower turgor pressure (ψp), poorer stomatal control, higher cuticular conductance, and a lower bulk modulus of elasticity than expanded leaves. Stomatal closure occurred at a progressively lower leaf water potential (ψw) as leaves aged. Net CO2 assimilation rate and leaf conductance to water vapor (g1) of pecan in the field did not decline in response to high atmospheric water stress and minimum midday ψw of −1.4 to −1.9 MPa when trees were supplied with adequate soil moisture. Leaf elongation rate was exponentially related to with marked reductions in growth occurring at ψp below 0.6 MPa and a complete cessation in growth below ψp = 0.3 MPa. Net CO2 assimilation rates of expanded leaves were up to 22 μmol·s−1m−2, several times higher than previously reported. Net CO2 assimilation rate was not inhibited by 41.5°C leaf temperature, 2000 μmol·s−1m−2 photosynthetic photon flux, and 3 kPa vapor pressure deficits (VPD). Transpiration rate (E) increased greatly with increasing VPD. Values of gl and E were generally higher than those reported for woody C3 perennials. The efficient water transport system of pecans under conditions of nonlimiting soil moisture may be a consequence of evolution in a floodplain ecosystem.

Open Access

Abstract

Volume flux (Jv), solute flux (Js), and the chemical profile of xylem exudate from cut shoots of ‘Noble’ and ‘Welder’ muscadine grapevines [Vitis rotundifolia (Michx.)] were analyzed as a function of temperature and temperature preconditioning. The effects of short-term (i.e., 2-hr) temperature changes on Jv, xylem fluid osmotic potential (Ψs) and Js from bleeding ‘Noble’ grapevines were determined. The effects of 10 days of preconditioning temperature (4 to 8C or 22 to 28C) on ‘Noble’ and ‘Welder’ were monitored at 25C in relation to Jv, Ψs, Js and inorganic element, amino acid, organic acid, and sugar composition of xylem fluid. Short-term temperature changes induced marked increases in Jv (Q10 = 2.0) and Js but little alteration in Ψs. Temperature-preconditioning effects were cultivar-dependent. Js was enhanced ≈2-fold for both cultivars when preconditioned at 22 to 28C. The stimulation in Js of ‘Noble’ was a result of increased solute concentration (reduced Ψs); increased Js of ‘Welder’ was associated with increased Jv. We propose that the increase in Js with a concomitant increase in Jv of ‘Welder’ was due to a change in hydraulic conductance. Conversely, the increase in Js of ‘Noble’ was due to an increased solute concentration in cells surrounding the xylem vessels and/or to changes in membrane permeability to solutes. Temperature preconditioning had a substantial effect on inorganic ion, amino acid, organic acid, and sugar profile in xylem exudate of ‘Noble’, yet the chemical profile of ‘Welder’ was not altered. The physiological basis for this cultivar-dependent preconditioning response is discussed.

Open Access

Abstract

The 1st year performance of ‘Vidal Blanc’ and ‘Chancellor’ European-American grape cultivars was evaluated in a drought year. The most favorable treatment on plant water relations and vine growth was soil profile modification with irrigation (MI), followed by no soil profile modification with irrigation (Cl), soil profile modification without irrigation (MN), and no soil profile modification without irrigation (CN). Leaf conductance (kl), transpiration, vine height, leaf number, average leaf area, and total estimated leaf area were increased 2 to 7 times with irrigation. ‘Vidal Blanc’ seems to be better adapted than ‘Chancellor’ to low soil moisture conditions. Irrigation was consistently more beneficial than soil profile modification in the establishment year.

Open Access

Abstract

Paclobutrazol was applied 30 Mar. 1984 as a soil drench to 3rd-leaf pecan [Carya illinoensis (Wangenh.) C. Koch] ‘Cheyenne’ at concentrations between 0.05 to 2.60 g a.i./cm2 trunk cross-sectional area. Paclobutrazol inhibited tree growth, shoot extension, and trunk and limb growth during 1984 and 1985. Relative water content of leaflets was positively related and leaflet area was negatively related to paclobutrazol concentration. Paclobutrazol promoted lateral branching on a unit length basis on 1983 wood, although no significant relationship was apparent on 1984 wood. Leaflet weight under stress and turgid conditions was reduced with increasing paclobutrazol concentration. Net CO2 assimilation rate, leaf conductance, transpiration rate, leaf chlorophyll, and kernal weight measured during 1985 were not affected by paclobutrazol. The effects of soil-applied paclobutrazol under field conditions persist at least 3 years. Chemical name used: P-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Open Access

Abstract

Some aspects of senescence and bud hardiness of young ‘Vidal blanc’ and ‘Chancellor’ French-American grapevines in the following treatments were evaluated: soil profile modification plus irrigation (MI), no soil profile modification plus irrigation (Cl), soil profile modification without irrigation (MN), and no soil profile modification without irrigation (CN). After a prolonged summer drought, abundant fall precipitation increased 25 Oct. chlorophyll and leaf N levels for nonirrigated vines. In contrast, leaf P and K were higher for irrigated treatments. Bud hardiness of ‘Chancellor’ was greater than ‘Vidal blanc’ for all except the Cl treatment. Maximum primary bud hardiness was achieved in the Cl and MN treatment for ‘Vidal blanc’ and ‘Chancellor’, respectively. Cambium damage and/or plant death occurred for only ‘Vidal blanc’ in the CN treatment.

Open Access

Abstract

A technique is described whereby osmotic potential, turgor potential and total fruit water potential can be determined quickly in the field with the aid of a pressure bomb, a hand held refractometer, and a percent soluble solids to osmotic potential conversion chart. A unique inverse linear relationship between percent soluble solids and osmotic potential was found for each fruit species. Application of this technique to rain cracking of ‘Napoleon’ sweet cherries (Prunus avium L.) shows that cracking is not strictly related to percent soluble solids, osmotic, turgor, or fruit water potential. This suggests that the degree of cuticular permeability, cuticular strength, cell wall strength or other factors may be of greater importance in determining cracking susceptibility than water potential parameters.

Open Access