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Open access

D. D. Mathur, R. H. Stamps, and C. A. Conover

Abstract

Reduction of irrigation level on leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching] to 150 cm/year from 311 cm/year (recommended rate) had no effect on frond yield or fresh weight and increased vase life on 3 of 7 harvest dates. Nitrogen sources of urea or NH4NO3 did not affect frond yield or fresh weight, but there were some minor variable effects on vase life.

Free access

Robert H. Stamps and Daniel W. McColley

Established ground beds of leatherleaf fern were sprayed repeatedly with water, a flowable formulation of thiophanate-methyl, or one of four formulations of chlorothalonil on a predominantly weekly schedule. None of the treatments produced visible phytotoxicity symptoms or had any effect on yield (frond number and total fresh mass). However, average masses of fronds from plots treated with a liquid formulation of chlorothalonil were 21% greater than those from control plots. All chlorothalonil formulations left visible residues on the fronds and reduced frond vase life compared to fronds treated with water or thiophanate-methyl. Reduced vase life was due to more rapid desiccation of chlorothalonil-treated fronds. During those months (July—Sept.) when postharvest desiccation is most common, chlorothalonil reduced vase life of fronds by 36% to 62%. Vase life of fronds was generally reduced more by dry chlorothalonil formulations than by liquid ones, probably due to slightly higher application rates of dry formulations. Determination of the mode of action could lead to an understanding of the causes of frond curl syndrome. Until a remedy is found, chlorothalonil should not be used repeatedly on leatherleaf fern. Chemical names used: tetrachlorisophthalonitrile (chlorothalonil); dimethyl [(1,2-phenylene)-bis(iminocarbonothioyl)]bis[carbamate]) (thiophanate-methyl).

Open access

Terril A. Nell, James E. Barrett, and Robert H. Stamps

Abstract

Leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching] fronds became desiccated rapidly after harvest with water potential decreasing from -0.45 to -1.75 MPa within 30 minutes. Partial closing of stomates 30 minutes after harvest accounted for a decrease in the rate of frond desiccation and frond water potential was -2.26 MPa after 180 minutes. Postharvest frond desiccation to water potentials of -1, -2, and -3 MPa in the field prior to water dip and cold storage resulted in frond curl of 32, 56, and 84%, respectively, when placed in postharvest rooms. Water uptake decreased during the first 4 days in postharvest rooms. Declining frond water potentials suggested reduced rate of water uptake was due to blockage of the xylem. However, no obstructions were observed at cut end of stipe from fern with frond curl or those not exhibiting frond curl. Frond water potentials were lower one hour after harvest than when undergoing normal postharvest senescence. Fronds did not exhibit normal drought-imposed wilt or frond curl during prestorage stress. Desiccation resulted in frond curl in some experiments but had little effect in others. These results indicate that frond curl can be triggered by desiccation stress but other factors are predisposing fronds to this disorder.

Open access

R. H. Stamps and A. R. Chase

Abstract

Storage at 4.5°C prevented decay of cut fronds of leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching] artificially inoculated with Cylindrocladium heptaseptatum Sobers, Alfieri, & Knauss and/or naturally infected with C. pteridis Wolf and increased frond vase-life compared to 24° storage. Storage at 4.5° for 10, 21, and 31 days did not affect subsequent frond vase-life. Inoculation of fronds decreased vase life by 11% in one experiment and had no effect in a second. Prestorage dips in benomyl suspensions at concentrations as low as 38 ppm reduced frond decay by 82% when stored at 24° and increased vase-life of fern stored at both 4.5° and 24°. Benomyl [methyl l-(butylcarbamoyl)-2-benzimidazole-carbamate] dips at concentrations as high as 300 ppm had no detrimental effect on vase-life. Iprodione [3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide] had no effect on vase-life.

Open access

D. D. Mathur and A. S. Bhagsari

Abstract

The influence of photosynthetically active radiation (PAR) and temperature on net photosynthesis and dark respiration was determined on leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching] grown under 73% polypropylene shade. The maximum photosynthesis rate of 7.5 mg CO2 dm-2 hr-1 occurred at 500 μE m-2s-1 PAR. The light compensation point was 44 μE m-2s-1 PAR. A temperature of 20°C and 1000 μE m-2s-1 PAR was most favorable for net photosynthesis of leatherleaf fern. Use of the antitranspirant, a paraffin wax emulsion (Mobilcer A), at a 2% concentration reduced dark respiration by more than 50% and reduced net photosynthesis considerably compared to the control at 40°.

Open access

R. H. Stamps and D. D. Mathur

Abstract

Four herbicides, alone and/or in combination, were evaluated for weed control in beds of leatherleaf fern [Rumohra adiantiformis (G. Forst) Ching]. Fair winter weed, predominantly chick weed [Stellaria media (L.) Cyr.], control was obtained with simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 2 kg active ingredient (a.i.)/ha, simazine + metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 1.1 + 2.2 kg a.i./ha and oxadiazon [2-terf-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] + simazine at 1.1 + 1.1 kg a.i./ha. Oxadiazon + simazine, oxadiazon + metolachlor at 1.1 + 2.2 kg a.i./ha, and simazine + metolachlor controlled spring weeds. All herbicide treatments gave fair weed control in summer. Except for simazine applied alone, none of the treatments injured leatherleaf fern visibly. Oxadiazon + metolachlor, oxadiazon + simazine, and simazine + metolachlor reduced winter weeding times. All combination treatments reduced spring weeding times, but none of the treatments reduced summer weeding times. No treatment reduced fern yield or affected average frond weights. Frond length and frond weight were positively correlated (r = 0.74).

Open access

Robert H. Stamps and Richard T. Poole

Abstract

Effects of repeated applications of preemergence herbicides (alachlor, metolachlor, oxadiazon, and simazine) at 1 ×, 2 ×, and 4 × rates to leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] beds were studied. During the first two years of bed establishment, all herbicides reduced weed coverage compared to commercial practice (hand-weeding 3 times per year), but only simazine and oxadiazon suppressed weed coverage to commercially acceptable levels between hand-weedings. In year 3, when the fern beds had become well-established, all herbicide treatments provided adequate weed suppression. Simazine was phytotoxic to the fern and reduced yield. Metolachlor increased rhizome mortality compared to commercial practice. Herbicide and weed-free treatments had no effect compared to commercial practice on frond fresh and dry weights or postharvest water uptake and longevity of cut fronds. Chemical names used: 2-chloro-N-2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 2 chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 3-[2,4-dichloro-5-(l-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon); 6-chloro-N, N′-diethyl-1,3,5-triazine-2,4-diamine (simazine).

Free access

Robert H. Stamps

Four spunbonded crop covers were evaluated for use with and without irrigation for cold protection of leatherleaf fern [Rumohra adiantiformis (Forst.) Ching]. Heavier and less porous covers provided the most protection when used without over-the-crop irrigation. However, differences in cover weight and porosity did not affect temperatures under covers when over-the-crop irrigation was applied. Damage to immature fronds was decreased by 75% to 99% when the covers were used alone and by 98% to 99% when the covers were used with over-the-crop irrigation. Covers had no effect on frond vase life.

Free access

Robert H. Stamps, Terril A. Nell, and James E. Barrett

Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] fronds produced under a high-temperature regime (HTR, 30 day/25C night) grew faster and produced sori earlier than those in a low-temperature regime (LTR, 20 day/15C night). Abaxial diffusive conductance was lower for HTR-grown fronds. Light-saturated net CO2 assimilation rates (Pn) and dark respiration were lower for HTR fronds, but light-saturated Pn efficiencies (chlorophyll basis); light compensation points; and soluble sugars, starch, and nonstructural carbohydrate levels were similar for the two regimes. Transpiration and water-use efficiency (mass basis) at light saturation were similar for fronds from both temperature treatments. Comparison of physiological characteristics of fronds from the two temperature regimes revealed no differences that might account for reduced postharvest longevity of fronds produced at the higher temperatures.

Open access

R. H. Stamps, T. A. Nell, and D. J. Cantliffe

Abstract

Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] was grown in controlled environment chambers set for day/night temperatures of 35/24C (high temperature regime, HTR) or 24/13C (low temperature regime, LTR). Fronds were harvested for vase life studies at 1100 and 1800 HR and held in holding rooms in deionized water. Plants were then moved to a greenhouse environment (16–25C) and, after 1 week, an additional set of fronds were harvested. Water uptake of harvested fronds declined exponentially and was generally lower for HTR fronds. HTR fronds had, for the most part, reduced vase life compared to LTR fronds. Most (81%) of the HTR fronds exhibited desiccation symptoms, whereas none of the LTR fronds did. These differences did not appear to be related to preharvest diffusive resistance or water potential differences.