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  • Author or Editor: G. Yelenosky x
  • Journal of the American Society for Horticultural Science x
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Abstract

Aqueous suspensions of ice nucleation active (INA) bacteria [Pseudomonas syringae van Hall and Erwinia herbicola (Löhnis) Dye] and suspensions of nonbacterial agents, silver iodide, phenazine, and flurophlogopite, were used to induce freezing in young citrus trees, ‘Valencia’ orange [Citrus sinensis (L.) Osbeck] on sour orange (C. aurantium L.) rootstock. Trees sprayed with INA agents froze at higher temperatures than unsprayed trees. INA bacteria-induced freezing was significant only when leaf surfaces were allowed to dry prior to freeze tests. Leaves with dry surfaces supercooled 1° to 3°C more than wet leaves, which started to freeze, and about 1° sooner with than without INA agents. Differences between INA bacteria and nonbacterial agents were not significant in the moment of freeze of wet leaves. INA agents induced freezing in citrus leaves usually before −5°, and in water drops, before −4°. Freezing was easier to induce on the underside (abaxial) than top (adaxial) surfaces of leaves. Sucrose, proline, and expressed sap were nonINA on citrus leaves and in drops of water.

Open Access
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Abstract

Potted citrus trees, 1-yr-old ‘Valencia’ orange (Citrus sinensis (L.) Osbeck) on 1.5-yr-old Rusk citrange (C. sinensis (L.) Osbeck × Poncirus trifoliata) rootstocks were maintained for 6 consecutive 7-day periods in a controlled environment to induce cold hardiness with cold-hardening temperatures 10 ± 1°C, illumination 500 μeinsteins/m2 per sec (photosynthetically active radiation = PAR), relative humidity, 60 ± 5%. Trees progressively cold hardened as a result of the above conditions and, after 5 weeks, would tolerate −6.7° for 4 hours without apparent injury. Leaves sustained injury up to 5 weeks and stems up to 3 weeks of cold hardening. Solutes increased most rapidly in leaves during the first week as a result of carbohydrate accumulation.

Proline, glutamic acid and valine increased, whereas other amino acids decreased. Water potentials in the leaves of hardened trees averaged −19.5 bars after 6 weeks of cold hardening compared to −5 bars in leaves of unhardened trees.

Open Access
Authors: and

Abstract

Four-year-old ‘Marsh’ grapefruit (Citrus paradisi Macf.) trees on trifoliate orange [Poncirus trifoliata (L.) Raf.] rootstock were temperature acclimated to 5°C in controlled environment facilities with approximately 400 μeinsteins m−2s−1 PAR. Total soluble carbohydrates and proline increased in both leaves and fruit flavedo as temperatures were progressively decreased. Maximum accumulation of carbohydrates occurred in leaves and flavedo at 10° ambient air. Both sucrose and reducing sugars increased in leaves at all acclimating temperatures, but only reducing sugars increased in the flavedo at temperatures below 15°. The concentration of proline was the greatest in the leaves and flavedo at 5°. Both total soluble carbohydrates and proline decreased during temperature deacclimation at 25°.

Open Access

Abstract

Initial growth and development of ‘Valencia’ orange [Citrus sinensis (L.) Osbeck] shoots from buds grafted on 7 different rootstocks were determined during cold-hardening and nonhardening temperature regimes for the 1st 4 months after budbreak. Cold hardening included 12 hr each of 15.6°/4.4°C day/night (D/N) in controlled-environment rooms, where 80% fluorescent and 20% incandescent light averaged 450 μmol m-2s-1. Nonhardening included 32.2°/21.1° D/N as well as greenhouse conditions with natural daylight. Rootstocks influenced growth of ‘Valencia’ during cold-hardening temperatures. Cold-hardening temperatures, however, did not stop ‘Valencia’ growth on any of the rootstocks. Total growth was less than 1/20 of the dry weight accumulated during the warm temperatures. During the cold-hardening treatment, ‘Valencia’ grew the most on the relatively cold-tender volkamer lemon [C. volkameriana (Ten. and Pasq.)] rootstock. The least growth was on the more cold-hardy Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliata (L.) Raf.] rootstock. The amount of growth during cold-hardening temperatures generally coincided with the cold hardiness of the rootstocks, but statistical separation was poor. Trees grown at the warm temperatures started to freeze at higher temperatures than trees grown at cold-hardening temperatures. Rootstocks did not influence freeze avoidance, and no differences were apparent in freeze (ice) tolerance. Three layers of palisade cells were found in leaves that were grown at the cold temperatures.

Open Access

Abstract

In the article “Growth Capacity of ‘Valencia’ Orange Buds on Different Rootstocks during Cold-hardening Temperatures” by G. Yelenosky and H.K. Wutscher [J. Amer. Soc. Hort. Sci. 110(1):78–83. 1985.], the figure captions for Figures 2 and 3 were reversed.

Open Access

Abstract

In the paper, Distribution of l4C Photosynthetic Assimilates in ‘Valencia’ Orange Seedlings at 10° and 25°C by C. L. Guy, G. Yelenosky, and H. C. Sweet (J. Amer. Soc· Hort. Sci. 106(4):433–437. 1981) the title for Table 1 should read: l4C-labeled fractions extracted from ‘Valencia’ orange seedlings exposed to l4CO2 (50 μCi for 3 hours) at 25° and 10°C and maintained at those temperatures for 28 days in controlled temperature light rooms.

Open Access

Abstract

The distribution of 14C-photosynthate was determined in 8-month-old potted ‘Valencia’ orange seedlings [Citrus sinensis (L.) Osbeck] during 25° and 10°C temperature regimes. Seedlings were pulse-labeled with 14CO2 for 3 hr after equilibration with ambient air. Radioactive assimilates were extracted at selected intervals, from leaves, stems, and roots and separated into several biochemical fractions. Low-temperature (10°) exposure resulted in a greater retention of 14C in the sugar fraction of leaves and a lower rate of 14C incorporation into organic and amino acid fractions. Data indicate a lower rate of metabolism of photosynthate and a reduced distribution of 14C in citrus seedlings at 10° than at 25°C.

Open Access