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Felix Loh, Jason Grabosky, and Nina Bassuk

The Minolta SPAD meter has been used to evaluate chlorophyll concentration in plant material to provide an inexpensive method to collect rapid, nondestructive data. Correlations of SPAD data and chlorophyll concentrations in corn have been very accurate r 2 = 0.95), and can be used to monitor plant nutrient status as a function of chlorophyll concentration. There has been evidence that the calibrated accuracy of the SPAD meter is diminished at low and high concentrations of chlorophyll. Our study attempted to build the same type of background information for two tree species for use in evaluating plant response in experimental media experiments. Ficus benjamina L. and Populus deltoides Marsh were grown in containers of varied media. Leaf tissue was measured with a Minolta SPAD-502, and the tissue was then removed and processed with N,N-dimenthylformamide for analysis in a spectrophotometer. The remainder of the leaf sample was analyzed in an ICAP for tissue nutrient levels. Data were analyzed to evaluate the usefulness of the SPAD meter for woody plant leaf tissue evaluation and to develop calibration curves for use in future studies. There was a positive correlation (r 2 = 0.943 in Ficus) between SPAD data and combined concentrations of chlorophyll a and b. Accuracy of the SPAD data was diminished when chlorophyll concentrations were low (SPAD <20, chorophyll <450 μg·mL-1) and high (SPAD >45, chorophyll >1350 μg·mL-1)..

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Thaddeus McCamant and R. Alan Black

Cold hardiness was studied in two interspecific Populus hybrids (P. trichocarpa × P. deltoides, and P. trichocarpa × P. maxomowiscii), using laboratory freezing tests of mid-winter dormant tissues and fully expanded leaves in the autumn. These laboratory measurements were compared to field observations. Hybrids having one parent from southern-source populations and the other parent from northern sources were compared to hybrids in which both parents were from southern-source populations. Populus hybrids with one parent of northern origin were generally hardier than hybrids from parents of southern sources; however, significant differences in cold hardiness were detected between hybrids having the same genetic parents. Field observations generally supported laboratory measurements and showed clonal differences in mid-winter cold hardiness and autumn leaf frost tolerance. Fully expanded leaves of different clones from the same parent also exhibited differences in frost tolerance.

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Zoran Jeknic and Tony H.H. Chen

In poplar (Populus deltoides Bartr.ex Marsh), the development of bud dormancy is initiated by short-day (SD) photoperiods. The degree of bud dormancy, expressed as days to budbreak, increased from ≈10 days for plants grown under long-days to >200 days after 10 weeks of SD exposure. We investigated quantitative and qualitative changes in protein fractions extracted from terminal buds, lateral buds, bark, and leaves of poplar plants during the induction of bud dormancy by 2-D PAGE. While total protein contents(as milligrams per gram fresh weight) in leaves, terminal, and lateral buds did not change significantly during SD treatment, bark protein content increased about five-fold in 10 weeks. The results of 2-D PAGE analysis indicated that there was a significant change in protein profiles in terminal and lateral buds, leaves, and bark. The results suggested that SD treatment in poplar plants causes substantial changes in protein profiles during the induction of bud dormancy.

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John M. Englert, Gary D. Coleman, Tony H.H. Chen, and Leslie H. Fuchigami

A 32kDa bark storage protein (BSP) which accumulates in the fall and is degraded in the spring has been identified in Populus deltoides bark. The BSP gene has been shown to be regulated by short day (SD) photoperiod (8 h). The physiological condition of the plant and the environmental factors necessary for the degradation and retranslocation of BSP are of considerable interest for determining the role of this protein in the remobilization of nitrogen in trees.

Poplar plants were placed in a SD growth chamber for 4 or 7 weeks to induce growth cessation (bud set) or dormancy, respectively. BSP accumulated to high levels in bark tissues after 3 weeks SD and remained high through 7 weeks SD. Plants in which growth had stopped (4 weeks SD), or in which dormancy (7 weeks SD) was broken with hydrogen cyanamide (0.5 M) or chilling (4 weeks 0C) broke bud within 1 week of being placed into long day (LD) conditions. Dormant plants which were not chilled broke bud after 3 weeks LD. BSP levels decreased around the time of budbreak, suggesting that the degradation of BSP is dependent on the need for a nitrogen sink, ie. budbreak and new shoot growth.

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M. Pilar Bañados, Gary D. Coleman, and Tony H. H. Chen

In poplar (Populus deltoides) a 32kDa bark storage protein (BSP) accumulates during the fall, and is a major form of stored nitrogen during overwintering. This protein is induced by short-day (SD) photoperiod and may play an important role in nitrogen cycling in the plant. To determine the effect of plant nitrogen status upon BSP gene expression, poplar plants were grown in controlled environmental chambers under either SD or long-day (LD) photoperiods and watered with either 5, 10, 50, and 100 mM NH4NO3 for four weeks. [15N]-NH4NO3 was applied during the first and third weeks. SDS-PAGE and western blot analysis were used to detect the relative amounts of BSP. RNA gel blot analysis was used to determine the changes in BSP gene expression. BSP accumulation was enhanced by increasing levels of nitrogen under both photoperiods, however, SD photoperiod appears to moderate the response. These results indicate that BSP gene expression is dependant upon the nutritional status of the plant. [15N] analysis will also be presented.

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Felix C. W. Loh, Jason C. Grabosky, and Nina L. Bassuk

A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the chlorophyll and nitrogen (N) status of benjamin fig (Ficus benjamina) and cottonwood (Populus deltoides) to quantitatively evaluate foliage quality. The goal was to provide a specific calibration for interpreting SPAD data within a media study for each species. Triplicate SPAD readings were collected from each of six leaves, sampled from forty plants per species, then processed for foliar analysis. Leaf tissue disks were also collected directly over SPAD testing sites for chlorophyll concentration measurement. Significant linear correlations were found between SPAD data and chlorophyll concentrations (r 2 = 0.90 in benjamin fig and r 2 = 0.91 for cottonwood). A significant, but lower correlation was found between SPAD data and N concentration. The SPAD-N correlations improved from the fifth month to the ninth month harvest (r 2 = 0.32 to 0.53 for benjamin fig and 0.26 to 0.42 for cottonwood). The SPAD-502 could be useful for in landscape plant management, and in time for production situations, but baseline data is needed. Consistent protocol in sample collection and seasonal timing is needed prior to use as a predictor for tissue N levels. Development of species, and perhaps cultivar, specific baseline data and sampling procedures will need development, but could yield a rapid, quantitative, in expensive field diagnostic for foliage quality for making cultural management decisions.

Open access

Weibing Zhuang, Xiaochun Shu, Xinya Lu, Tao Wang, Fengjiao Zhang, Ning Wang, and Zhong Wang

, colored-leaf plants, which have a wide range of applications in courtyard embellishment, road greening, garden set King, and so on, are increasingly popular ( Zhuang et al., 2019 ). Since the first colored-leaf poplar cultivar Populus deltoides Zhonghong

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Pinghai Ding, Leslie H. Fuchigami, and Carolyn F. Scagel

The accuracy of nondestructive optical methods for chlorophyll (Chl) assessment based on leaf spectral characteristics depends on the wavelengths used for Chl assessment. Using spectroscopy, the optimum wavelengths (OW) for Chl assessment were determined by using 1-year-old almond (Prunus dulcis), poplar (Populus trichocarpa × P. deltoides), and apple (Malus ×domestica) trees grown at different rates of nitrogen fertilization to produce leaves with different Chl concentrations. Spectral reflectance of leaf discs was measured using a spectroradiometer (300 to 1100 nm at 1-nm intervals), and total Chl concentration in leaf discs was extracted and determined in 80% acetone. The OW for nondestructive Chl assessment by reflectance spectroscopy was estimated using 1) the coefficient of determination (r 2) from simple linear regression; 2) reflectance sensitivity analysis (a measure for changes of spectral reflectance on unit change in leaf Chl concentration); and 3) the first spectral derivative method. Our results indicated that the first derivative method can be used only to identify OW in the red edge region of the spectrum, whereas r 2 and reflectance sensitivity analysis can be used to identify the OW in both the red edge and green regions. Our results indicate that using simple linear r 2 in combination with reflectance sensitivity and/or the first derivative analyses is a reliable method for determining OW in plant leaves tested. Two optimum wavebands with larger r 2, smaller root mean square error, and higher reflectance sensitivity were found in red edge (700 to 730 nm) and green (550 to 580 nm) regions, respectively, which can be used as common OW for Chl reflectance assessment in poplar, apple, and almond leaves tested. Single-wavelength indices if developed with OW were even more accurate than those more wavelength indices that developed without using OW. The accuracy of indices can be further improved if indices developed by using one OW and one Chl-insensitive wavelength from near infrared (NIR) (750 to 1100 nm) in the form of RNIR/ROW or (RNIR – ROW)/(RNIR + ROW).

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Manuela Baietto and A. Dan Wilson

and natural forest stands of temperate forests and the lower Mississippi Delta region: Fraxinus pennsylvanica Marsh., Liquidambar styraciflua L., Platanus occidentalis L., Populus deltoides Bartr. ex Marsh., Quercus lyrata Walt., Quercus

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Hailin Shen, Zhendong Liu, Ke Yan, Liren Zou, Jinghui Wen, Yinshan Guo, Kun Li, and Xiuwu Guo

, in model II, flower development bypasses the bisexual stage, and both the stamen and pistil primordium do not occur. Spinacia oleracea ( Sherry et al., 1993 ), Thalictrum dioicum ( Di Stilio et al., 2005 ), Populus deltoides ( Kaul, 1995 ), and