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- Author or Editor: Harold E. Moline x
Abstract
Four seedlings derived from 3 cultivars of Coleus Χ hybridus Voss and C. blumei Benth were injured when exposed to 5°C for 24, 32, or 48 hours. An exposure of 32 hours or longer increased the foliar damage of chilled seedlings. In the case of ‘Harlequin’ and ‘Weimar Buckley’ seedlings, chilling injury was apparent during or immediately following the 24, 32, and 48 hours chilling exposure. One selection of ‘Red Rainbow’ displayed no symptoms of chilling injury following the 24-hour treatment, and only minor injury after 32- and 48-hour exposure. The other selection was only slightly more sensitive following these treatments. Seven days after a 48-hour exposure at 5°, 100% of the terminal buds of ‘Red Rainbow’ and ‘Weimar Buckley’ seedlings were dead, but no damage was evident on terminal buds of ‘Harlequin’ seedlings. No apparent injury was observed in any seedlings when exposed to 10° for as long as 48 hours.
The antifungal properties of a hydrophobic neem (Azadirachta indica A. Juss.) seed extract (clarified neem oil) were tested against three postharvest apple (Malus domestica Borkh.) pathogens—Botrytis cinerea (pers.) ex Fr. (gray mold), Penicillium expansum Thom. (blue mold rot), and Glomerella cingulata (Ston.) Spauld. & Schrenk. (bitter rot). The antifungal activity of neem seed oil also was compared to that of CaCl2. A 2% aqueous emulsion of the clarified neem seed oil was moderately fungicidal to B. cinerea and G. cingulata in inoculated fruit, but bad little activity against P. expansum. Ethylene production was reduced 80% in fruit dipped in 2% neem seed oil compared to wounded, inoculated controls. Neem seed oil was as effective an antifungal agent as CaCl2, but the effects of the two combined were not additive.
Abstract
Intact plants of a green-leafed strain of Coleus blumei Benth. (PI 354190) were exposed to 5°C for 48 or 72 hr after pretreatment for 48 hr at two levels of photosynthetic photon flux (PPF) (8 or 320 μmol·s−1·m‒2) at two temperatures (13° or 20°). Plants were sprayed with two abscisic acid (ABA) levels (0 or 200 g·m‒3) either 0 or 48 hr before chilling. Postchilling condition of the plants was assessed by comparing the time courses of refreshed (cyclically excited and measured) delayed light emission (RDLE) and fluorescence (FLU) from dark-equilibrated leaves. Greater suppression of RDLE and FLU indicates greater injury. Plants pretreated at 8 μmol·s−1·m‒2 PPF showed less suppression of RDLE and FLU, contained more chlorophyll, and showed less injury than did plants pretreated at 320 μmol·s−1·m‒2 PPF. Increasing the duration of chilling from 48 to 72 hr reduced the maximum RDLE and FLU slightly. Pretreatment temperatures and ABA concentration had negligible effects on RDLE and FLU levels. The maximum RDLE, the RDLE level at 7.5 sec, the maximum FLU, the FLU at 1.5 sec, and variable FLU were the measurement variables most responsive to individual and combined treatment effects. Maximum RDLE from upper leaf surfaces was the measurement most responsive to the combined effects of all treatments. Chemical name used: [S-(Z,E)]-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2,4-pentadienoic acid [abscisic acid (ABA)].