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M. Faust, A. Erez, L.J. Rowland, S.Y. Wang, and H.A. Norman

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James M. Wargo, Ian A. Merwin, and Christopher B. Watkins

`GoldRush' is a new scab (Venturia inaequalis) resistant apple (Malus ×domestica) with excellent flavor and storage qualities that tends to produce small and russeted fruit. We investigated the effects of rate, timing, and method of nitrogen (N) fertilizers on `GoldRush' fruit size and quality during 1998-99. Fertilizer treatments were 1) no N fertilizer (control); 2) a low N rate of 45 kg·ha-1 (40.1 lb/acre) applied in April (LN-Apr); 3) a low N rate of 45 kg·ha-1 applied half in April and half in June (LN-Apr+Jun); 4) a high N rate of 90 kg·ha-1 (80.3 lb/acre) split in April and June (HN-Apr+Jun); 5) a high N rate of 90 kg·ha-1 applied in April, May, June, and July at 22.5 kg·ha-1 (20 lb/acre) each month (HN-Apr+May+Jun+Jul); and 6) canopy sprays of 1% (wt/wt) urea-N, equivalent to 7 kg·ha-1 (6.2 lb/acre) applied monthly in May, June, July, and August (foliar urea). In 1998, an additional foliar urea spray at 5% (wt/wt) concentration was applied to trees after harvest. The first year's Ntreatments did not affect relative average fruit weights or total yields, but unfertilized trees produced more fruit in smaller size categories. Nitrogen fertilization resulted in greener and softer fruit both years. In the second year, all N additions increased yields compared with controls, but average fruit weight was inversely correlated with crop load. Foliar urea sprays and HN-Apr+May+Jun+Jul treatments increased yields the most. Fruit from LN-fertilized trees were normally distributed across a range of eight box-count size categories, peaking at size 100 both years. In the unfertilized control, fruit size was skewed into smaller size categories and yield was reduced. Total yields were greatest in foliar urea and HN-Apr+May+Jun+Jul treatments, but fruit-size distribution was skewed into smaller categories, peaking at size 138 in the second year. Foliar urea and HN-Apr+May+Jun+Jul treatments produced the highest crop value, but when estimated labor and fertilizer costs were considered, foliar urea and LN-Apr+Jun were the most efficient treatments. Nitrogen fertilizer improved fruit size and market value, but average fruit size in all treatments remained relatively small in both years, indicating that N fertilization alone may not increase fruit size in `GoldRush.'

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William R. Graves and Lorna C. Wilkins

Growth of honey locust (Gleditsia triacanthos var. inermis Willd.) seedlings was studied during exposure to reduced osmotic potential (ψπ) and high temperature in the root zone. Half-sib plants were cultured in solution. Root-zone temperature was increased from ambient (23C) to 35C for 0, 6, 12, or 24 hours·day -l. Within each temperature treatment, solution ψπ of -0.05, – 0.10, and – 0.20 MPa were maintained by additions of polyethylene glycol (PEG) 8000. Root and shoot dry weights decreased with increasing exposure to 35C among seedlings in -0.05-MPa solution and decreased for seedlings in - 0.10- and - 0.20-MPa solutions in all temperature regimes. Growth of epicotyls displayed similar trends, but epicotyls of plants in -0.20-MPa solution were longest with 6 hours·day-l at 35C. Significant interactions between effects of temperature and osmotic regimes indicated that water-stressed honey locust seedlings are relatively insensitive to elevated root-zone temperatures. However, related studies showed that PEG caused reductions in growth that could not be explained by decreases in ψπ and suggested that responses of honey locust to PEG differed from those when drought was imposed by withholding irrigation in an aggregate medium.

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Craig M. Hardner, Marisa Wall, and Alyssa Cho

, Hilo, HI. Summary of Presentations A total of 28 oral and seven poster presentations were delivered at the symposium (abstracts are included as a Supplemental File). Areas of research included propagation, tree physiology, soils and nutrition

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Hanan M. El-Hoseiny, Mohamed N. Helaly, Nabil I. Elsheery, and Shamel M. Alam-Eldein

and development ( Zuo et al., 2007 ). Application of HA and BA has improved overall tree physiology ( Tables 2 – 6 ) and led to reduced malformation percentage ( Table 7 ). Results displayed in Tables 3 and 7 confirm previous reports that have

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David B. Headley and Robert G. Mower

The color of a tree's canopy can provide much information about the tree's physiological status as well as its aesthetic function. We present a system for the qualitative and quantitative analysis of tree canopy color, based on a previously published algorithm. This algorithm determines (with a known accuracy) the Munsell hue, value, and chroma of a color using densitometric readings obtained through the use of color separation filters. This method was adapted for use with black-and-white video images. Combining the Rib algorithm with the techniques of photography, video imagery, scanning microdensitometry, and batch data computer processing, a semi-automated system was devised for the pixel-by-pixel color evaluation of a 512 × 512-pixel image. Based on a sample of 251 color chips, the following accuracies were obtained: Munsell hue—86%, Munsell value—93%, Munsell chroma—70%, and Munsell color—62%. An example is provided that demonstrates how this system may be used to determine tree canopy color. By employing this technique, an estimation may be made of the colors and their relative quantities that are displayed by a tree's canopy.

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Dr. Mustafa Erkan

Horticultural Development” for the ASHS annual meetings. She served on the editorial review board of Tree Physiology and the screening committee for fruit publication award for ASHS. During the course of her career, Dr. Wang mentored many visiting scientists

Open access

Giverson Mupambi, Nadia A. Valverdi, Hector Camargo-Alvarez, Michelle Reid, Lee Kalcsits, Tory Schmidt, Felipe Castillo, and Jonathan Toye

subtropical fruit: Effect on environmental conditions, tree physiology and fruit quality Scientia Hort. 256 108556 doi: 10.1016/j.scienta.2019.108556 Meinhold, T. Damerow, L. Blanke, M. 2011 Reflective materials under hailnet improve orchard

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Ockert P.J. Stander, Jade North, Jan M. Van Niekerk, Tertia Van Wyk, Claire Love, and Martin J. Gilbert

., 2003 ; Stamps, 2009 ; Wachsmann et al., 2014 ). Often, the use of protective netting also results in changes in the orchard microclimate that can alter tree physiology and improve tree performance and fruit development ( Cohen et al., 2005 ; Manja

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Dinesh Phuyal, Thiago Assis Rodrigues Nogueira, Arun D. Jani, Davie M. Kadyampakeni, Kelly T. Morgan, and Rhuanito Soranz Ferrarezi

fruit quality. Citrus tree physiological function is negatively impacted by HLB ( Etxeberria et al., 2009 ; Gonzalez et al., 2012 ). Nwugo et al. (2013) found that HLB-affected grapefruit showed alteration of several foliar proteins due to nutrient