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  • Author or Editor: Barbara A. Lewis x
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Abstract

Weeping fig (Ficus benjamina L.) plants were greenhouse-grown under full sun or 75% light exclusion. Shade-grown leaves were larger, thinner, flatter, and darker green than sun-grown leaves. Sun- and shade-grown plants had the same total leaf area and were the same height. Shade-grown leaves had a single, poorly developed palisade layer with large chloroplasts dispersed throughout the palisade cells. Sun-grown leaves had one or two layers of well developed palisade cells with the chloroplasts aligned primarily along the radial walls. Stomatal density was greater in sun-grown leaves, but shade-grown leaves had more stomata per leaf.

Open Access

Abstract

Suitable conditions for determining net photosynthesis (Pn) of individual sun- and shade-grown leaves of weeping fig (Ficus benjamina L.) were 21°C dew point and an air flow rate between 1 and 3 liters/min. A diurnal trend in Pn occurred for sun leaves, with maximum rates between 0800 and 1200 hr; shade leaves did not decline in Pn until mid-afternoon. Leaves which originated from nodes 4 through 10 (from the shoot apex) did not differ in Pn, transpiration (Tr), specific leaf weight (SLW), or leaf water content. Shade-grown leaves had a photosynthetic advantage over sun-grown leaves at levels of photosynthetically active radiation (PAR) below 77 μE m−2s−1, whereas at PAR levels above 100 μE m−2s−1 the reverse was true. Sun-grown leaves had higher Tr rates than shade grown leaves at all PAR levels used.

Open Access

Abstract

Weeping Hg (Ficus benjamina L.) plants grown under 3 light regimes (full sun, full sun followed by 8 weeks acclimatization under 75% shade, and 75% shade) were placed in a low-light simulated interior environment (SIE) for 12 weeks. Acclimatized and shade-grown leaves had higher net photosynthesis (Pn) rates, lower dark respiration (Rd) rates, and lower light compensation points (LCP) than sun-grown leaves after 12 weeks in the SIE. No treatments increased total plant dry weight during the 12 weeks of SIE. However, percent dry matter of sun plants was redistributed with additional leaves produced at the expense of root carbohydrate reserves. Leaf production exceeded abscission in all treatments. Anatomical observations prior to and following the SIE indicated chloroplast reorientation in all treatments. The development of large, heavily stained chloroplasts suggest ultrastructural changes may also occur as a result of low light.

Open Access

In 1995, greenhouse and orchard experiments of 11 apple cultivars were conducted in Fayetteville and Clarksville, Ark. Weekly cumulative mite days (CMD) were regressed against leaf bronzing (colorimeter value L) and compared among cultivars. European red mites, Panonychus ulmi and two-spotted spider mites, Tetranychus urticae, were found on leaves. `Liberty', `Royal Gala', and `Stark Spur Red Rome Beauty' had significantly more mites (>1940 CMD) than did `Arkansas Black' (1303), `Jonafree' (1150), and `Northern Spy' (973). A low CMD on `Northern Spy' caused leaves to bronze faster [y = 29.04 + 0.006(x); R 2 = 52, P = 0.0002] than did a high CMD on `Liberty' [y = 30.41 + 0.0027(x); R 2 = 70, P = 0.0001]. Field estimates were made of spider mites/leaf and bronzing from 20 June to 7 Aug. `Stark Spur Red Rome Beauty' and `Stark Spur Law Rome' had significantly more CMD than did `Northern Spy' and `Arkansas Black'. Apple cultivars differed in carrying capacity to mites (susceptibility) and how fast leaves bronze in response to mite feeding. Cultivar differences in hairiness of the lower leaf surface were not correlated to CMD.

Free access

Since 1997, populations of Japanese beetle have settled into some of the major urban areas of Arkansas, especially Little Rock and Northwest Arkansas, due to transported turf and nursery material. Experimental trials at the University of Arkansas Agricultural Research and Extension Center, Fayetteville have sustained significant damage due to the increasing Japanese beetle population. Plantings of blackberries and blueberries were rated for feeding damage. Significant differences were observed among genotypes of both crops. Mean damage ratings varied from 0.6 to 4.0 for the blackberries and 1.2 to 3.5 for the blueberries. As evidenced by the mean damage ratings, some resistance or tolerance is present within these populations and may be exploited for improvement.

Free access