age or stage of development ( Tolman et al., 1990 ). For instance, Bryson and Mills (2014) reported an estimated age and where the leaf tissue was sampled by stating “mature leaves from new growth,” while Campbell (2000) only reported leaf tissue
, 2009 ). According to Schwab et al. (2008) , the international trade of essential oil increases annually on average by 10% a year. It is well documented that plant developmental stages as well as leaf ages have a strong effect on the volatile
( Snyder and Struve, 1997 ). The goal of this study was to determine the differences in leaf characteristics and nutrient concentrations resulting from position (north, south, east, and west directions) and age (early-season versus late-season leaves
commercially produced by greenhouses. Furthermore, little attention has been given to identifying nutritional sufficiency ranges of container-grown Perovskia by chronological age. Leaf tissue nutrient sufficiency ranges by chronological age for herbaceous
, leaf tissue nutrient sufficiency ranges by chronological age have only been reported for perennial hibiscus ( Hibiscus hybrid L. ‘Mocha Moon’ and ‘Starry Starry Night’; Owen, 2019 ). For annual bedding plants, leaf tissue nutrient sufficiency ranges
tissues ( Huang et al., 2004 ; Islam et al., 2002 , 2003b ; Walter et al., 1979 ). However, these previous studies provided no information regarding the effect of root size and leaf age on phenolic composition and antioxidant properties of sweetpotato
Two studies were conducted to assess the effects of leaf aging on gas exchange in okra [Abelmoschus esculentus (L.) Moench] leaves. Gas exchange was measured at 6- to 10-day intervals starting 15 days after leaf emergence (DFE) and continuing until senescence at 50 DFE. Rates of transpiration (E), stomatal conductance (gs) and CO2 exchange (CER) increased as leaves matured up to ≈25 DFE, about full leaf expansion. Transpiration rate, gs, and CER declined after 25 DFE and as leaves aged further. Internal leaf CO2 concentration (Ci) was higher in old than young leaves. This study suggests that the most efficient okra canopy would maximize exposure of 25-day-old leaves to sunlight.
Abstract
For all leaf ages of Rosa hybrida L. cv. Samantha, maximum photosynthetic rates were reached at irradiances of 450 to 500 μE m−2sec−1. The magnitude of this response decreased from 20.6 mg CO2 dm−2hr−1 in the youngest leaves studied to 15.4 mg CO2 dm−2hr−1 in the oldest. Maximum photosynthetic rates were reached before full leaf expansion. Mesophyll resistance, however, increased with age from 7.8 to 12.5 cm sec−1. CO2 compensation points and dark respiration decreased throughout most of leaf development, but increased slightly at the most advanced developmental ages studied. Photosynthetic enhancement, the percent increase in net photosynthesis at 2% O2 compared to 21% O2, averaged 33% for all leaves. There was no change in the amount of photosynthetic enhancement as leaves aged, indicating that changes in photorespiration were not a major factor in photosynthetic trends over the range of leaf ages examined.
The effects of shading and leaf age on the production of foliar phenolics of two apple (Malus domestica Borkh.) cultivars, `Liberty' and `Red Rome Beauty', were studied. Potted trees were grown outdoors and their leaves tagged weekly when they reached 20 mm in length. This process continued for the duration of the experiment. At 3 weeks from budbreak, the trees were placed in three shade treatments: 0% shade (control), 60% shade, and 90% shade. After 5 weeks, the leaves were collected for phenolic assay. Specific leaf weight (SLW) was determined from the leaf below the tagged leaf. Shade significantly affected the total phenolic content. Leaves in 0% shade had the highest levels of total phenolics. The phenolic content decreased with increasing shade, with trees in 90% shade having a 72% reduction in total phenolics. There was a significant shade by leaf age interaction. There was a decrease in total phenolic content with increasing leaf age except for those leaves whose development occurred before the experiment was started. The 1-week-old leaf had the highest phenolic content, while 4-week-old leaf had the lowest amount. The 5- and 6-week-old leaves that had been tagged prior to the onset of the shade treatments has similar phenolic content in all treatment. SLW significantly decreased with increasing shade and increased with leaf age. Results of this study indicate that light and leaf developmental stage are important factors in the total foliar phenolic content, but, once phenolics are synthesized, shading does not affect their content.
Effects of air temperature, relative humidity (RH), and leaf age on penetration of urea through isolated leaf cuticles of `Marsh' grapefruit (Citrus×paradisi Macfad.) trees on `Carrizo' citrange (C. sinensis L. Osbeck × Poncirus trifoliata (L.) Raf. rootstock were examined. Intact cuticles were obtained from adaxial surfaces of `Marsh' grapefruit leaves of various ages. A finite dose diffusion system was used to follow movement of 14C-labeled urea from urea solution droplets across cuticles throughout a 4-day period. Within the first 4 to 6 hours after urea application, the rate of urea penetration increased as temperature increased from 19 to 28 °C, but there was no further increase at 38 °C. Increasing relative humidity increased urea penetration at 28 °C and 38 °C. Cuticle thickness, cuticle weight per area, and the contact angle of urea solution droplets increased as leaves aged. Cuticular permeability to urea decreased as leaf age increased from 3 to 7 weeks, but permeability increased in cuticles from leaves older than 9 weeks. Contact angles decreased with increased urea solution concentration on leaf surfaces that were 6 to 7 weeks old, but solution concentration had no effect on contact angle on cuticles from younger and older leaves. Changing urea solution pH from 8.0 to 4.0 could have an effect on the amount of urea penetrating the cuticle through the loss of urea from breakdown possibly due to hydrolysis. Results from this study define leaf age, environmental conditions, and formulation for maximum uptake of foliar-applied urea.