Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: P.C. Andersen x
Clear All Modify Search
Free access

K.R. Woodburn and P.C. Andersen

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.

Free access

P.C. Andersen and W.B. Sherman

Free access

W.B. Sherman, P.C. Andersen and P.M. Lyrene

Free access

W.B. Sherman, P.C. Andersen and P.M. Lyrene

Free access

P.C. Andersen, W.B. Sherman and R.H. Sharpe

Free access

P.C. Andersen, W.B. Sherman and R.H. Sharpe

Free access

P.C. Andersen, B.V. Brodbeck and R.F. Mizell III

The Cohesion Tension Theory, first in 1894 introduced by Dixon and Joly is the theory most often invoked to explain water movement in a transpiring plant. The pressure chamber technique has provided the strongest indirect evidence for this theory. However, controversy remains because 1) the necessary pressure gradients in xylem vessels have never been measured directly; 2) it is uncertain how continuous water columns under great tensions could persist in a metastable state for extended periods of time, and; 3) direct pressure probe measurements on individual xylem vessels have not been indicative of the extreme negative pressures obtained with the pressure chamber. Xylem fluid is an energy-limited resource containing the lowest available carbon (energy content = 2 to 15 J/cm3) of any plant tissue. However, many species of xylophagous leafhoppers subsist entirely on this dilute food source, despite the negative pressures thought to occur in xylem vessels. Carbon limitations of leafhoppers were underscored by 1) high feeding rates; 2) an unprecedented assimilation efficiency of organic compounds (i.e., >99%); 3) ammonotelism, and; 4) synchronization of feeding to optimum host nutrient content both seasonally and diurnally. The maximum tension that can be generated by the cibarial pumping mechanism of an insect based on anatomy and biochemistry is about 0.3 to 0.6 MPa, far below the purported xylem tensions occurring during most daylight hours. By contrast, we have shown that feeding has been usually independent of xylem tensions, as measured with a pressure chamber, and instead was a function of the amide content of xylem fluid. Moreover, the calculated net energy gain of insect feeding (or that contained within insect biomass) on xylem fluid of a given composition under a given tension have also been an a paradox. Experiments will be described that provide insight into the energetics of xylem fluid extraction.

Free access

P.C. Andersen, J.G. Norcini and G.W. Knox

Leaf physiology and plant growth of Rhododendron × `Pink Ruffles' were compared under conditions of 100% sun and under polyethylene shadecloth with specifications of 69%, 47%, and 29% light transmittance. Net CO2 assimilation (A) and stomatal conductance to water vapor (gs) were often reduced for plants in the 100% sun regime, although few differences existed among the 69%, 47%, and 29% sun treatments. Stomatal conductance was very sensitive to leaf to air vapor pressure deficits (VPD), as evidenced by an 85% increase in gs with a decrease in VPD from 3.2 to 2.2 kPa. Light response curves established for plants after 54 days of exposure to 100% and 29% sun were similar, although A was consistently higher at all levels of photosynthetic photon flux for plants in the 29% sun regime. Maximum A was ≈5 and 6 μmol·m-2·s-1 for 100% and 29% sun-grown plants, respectively; light saturation occurred at ≈ 800 μmol·m-2·s-1 Midday relative leaf water content and leaf water potential were not affected by sun regime. The plant growth index decreased with increasing light level. Leaf, stem, and root dry weights; total leaf number and dry weight; total and individual leaf area; dry weight per leaf; and leaf chlorophyll concentration were reduced in 100% sun, yet few differences existed among the 69%, 47%, and 29% sun treatments. Shoot: root ratio and specific leaf weight were proportional to light level. Plants grown in the 100% sun regime were chlorotic and dwarfed, and plants in 29% sun were not sufficiently compact. One year after transplanting to the field under 100% sun, plants of all treatments were chlorotic and failed to grow.

Free access

J.G. Norcini, P.C. Andersen and G.W. Knox

Leaf physiology and plant growth of Photinia x fraseri Dress were assessed when grown under full sunlight or (100% sun) or polypropylene shadecloth with a light transmittance of 69%, 47%, or 29% sun. Plants in 69% or 47% sun usually had the highest midday net CO2 assimilation rates (A). Net CO, assimilation rate was most dependent on photosynthetic photon flex (PPF R2 = 0.60), whereas stomata] conductance to water vapor was primarily influenced by vapor pressure deficit (R2 = 0.69). Stomatal conductance was often inversely related to sun level, and intercellular CO2 concentration was often elevated under 29% sun. Midday relative leaf water content and leaf water potential were unaffected by light regime. Light-saturated A was achieved at ≈ 1550 and 1150 μmol·m-2·s-1 for 100% and 29% sun-grown plants, respectively. Under 29% sun, plants had a lower light compensation point and a higher A at PPF < 1100 μmol·m-2·s-1. Total growth was best under 100% sun in terms of growth index (GI) increase, total leaf area, number of leaves, and dry weight (total, stem, leaf, and root), although plants from all treatments had the same GI increase by the end of the experiment. Plants in all treatments had acceptable growth habit (upright and well branched); however, plants grown in 29% sun were too sparsley foliated to be considered marketable. There were no differences in growth among the four treatments 7 months after the Photinia were transplanted to the field.

Free access

S.M. Olson, D.O. Chellemi and P.C. Andersen

Since the fall of 1986, tomato growers in northwestern Florida and southwestern Georgia production areas have encountered plants in their fields with unusual growth characteristics. Early symptoms consist of interveinal chlorosis of the young leaves. Subsequent top growth becomes severely distorted with leaflets along the midrib failing to expand properly, resulting in a “little-leaf” appearance. Additional symptoms included cessation of terminal growth, leaves with twisted and brittle midribs, and axillary buds failing to develop properly. Fruit that set on mildly affected plants are distorted, with radial cracks extending from the calyx to the blossom scar. In severely affected plants, fruit failed to set. The problem usually occurs at very low levels, but in 2 years since 1986, the problem has caused some economic damage. To determine a possible cause, samples were taken for virus detection. None were detected in affected plants. Samples were also taken of tissue and soil from affected areas for nutrient and pesticide analysis. No explanation could be developed from any of the tissue or soil samples. The problem usually occurs in wet areas and after very warm temperatures. The problem appears to be very similar to a nonparasitic disease that occurs in tobacco, called “frenching.” In tobacco, frenching occurs in wet, poorly aerated soils with a soil pH >6.3 and during warm temperatures. There seems to be an organism or organisms present under certain conditions that live on the root surface and exude chemicals that cause this distorted growth.