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Ustun Sahin, Melek Ekinci, Fatih Mehmet Kiziloglu, Ertan Yildirim, Metin Turan, Recep Kotan, and Selda Ors

Water deficit is one of the main constraints affecting plant growth and crop yield in arid, semiarid, and even in humid areas, causing the fatal economic losses in agriculture ( Marulanda et al., 2009 ; Sandhya et al., 2010 ). Drought has been

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Jenjira Chumpookam, Huey-Ling Lin, and Ching-Chang Shiesh

improve the growth and yield of agricultural and horticultural species ( Brown et al., 2003 ), although it is necessary to dilute the concentration of the smoke-water before application to many species ( Lloyd et al., 2000 ). The main active germination

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Panpan Meng, Ying Ge, Qianjin Cao, Jie Chang, Peng Pan, Chi Liu, Yijun Lu, and Scott X. Chang

species respond to shade in cultivation, both in terms of growth rates and ornamental value, can greatly affect the commercial production of those species for the horticulture industry. The objective of this study was to investigate the responses in

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Jing Huang, Ya-liang Xu, Fa-min Duan, Xu Du, Qi-chang Yang, and Yin-jian Zheng

Light is one of the most important environmental factors regulating plant growth, development, and photosynthesis ( Claypool and Lieth, 2020 ; Ouzounis et al., 2015 ). Lighting-emitting diodes (LEDs) are regarded as the most effective light source

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Zhongjie Ji, James J. Camberato, Cankui Zhang, and Yiwei Jiang

Salinity stress can severely inhibit plant growth and development. The adverse effects of salinity stress on plants are generally imposed through osmotic stress by limiting water uptake and excessive uptake of sodium (Na + ) ions ( Munns and Tester

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Tonghua Pan, Juanjuan Ding, Gege Qin, Yunlong Wang, Linjie Xi, Junwei Yang, Jianming Li, Jing Zhang, and Zhirong Zou

et al., 2007 ). Numerous studies have shown that CO 2 enrichment can increase growth, affect physiology, and increase both yield and quality in tomatoes ( Mamatha et al., 2014 ; Nilsen et al., 1983 ; Yelle et al., 1990 ). Atmospheric CO 2

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Rizwan Maqbool, David Percival, Qamar Zaman, Tess Astatkie, Sina Adl, and Deborah Buszard

soil factors results in tremendous amount of uncertainty in wild blueberry nutrient management ( Percival and Sanderson, 2004 ). Plant growth and development (shoot number and fruit development) can almost double when ammonium is used instead of nitrate

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L. Eric Hinesley and Scott A. Derby

Fraser fir [Abies fraseri (Pursh) Poir.] Christmas trees were sheared once annually over 4 years on dates ranging from July to March. Shearing reduced total tree growth. Trees sheared in July and August had the highest quality and retail value. Early shearing (July and August) yielded fewer leaders, longer leaders, and 35% to 66% more internodal branches on the leader, compared to later shearing (September through March). Early shearing also yielded more second-order laterals, followed by greater elongation of those laterals. Shearing late into the fall yielded progressively fewer branches, with the minimum in October. Shearing in March gave a little better results than October, but neither date was as good as July or August. In one experiment, two types of residual tip buds (bubble and whisker) were compared as future leaders. Differences in length and straightness of leaders derived from whisker and bubble buds were considered negligible in commercial shearing practice. The ratio of adaxial and abaxial buds on the proximal portion of the leader was about 1:1, and showed little change with shearing date. Distance from the base of the leader to the first abaxial branch also showed little variation among shearing dates.

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G.H. Neilsen, J. Beulah, E.J. Hoguel, and R.S. Utkhede

Apple seedling height after 7 weeks of growth in greenhouse pots was compared with total first year shoot growth of `McIntosh' or `Delicious' apple trees [Malus domestica (Borkh.)] on M.26 rootstock for eight orchards and five soil treatments. The apple trees were replanted in old orchard sites with the same treatments applied in the planting hole as were tested in the greenhouse. The pot test successfully predicted treatments that increased first year shoot growth in 23 of 30 opportunities. However, a less precise relationship (R2 = 0.38) existed between total first year shoot growth (Y) of `Summerland Red McIntosh' on M.26 rootstock and seedling height (X).

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Mosbah M. Kushad

Polyamines and the activities of their biosynthetic enzymes were evaluated during peach (Prunus persica L. `Biscoe') mesocarp (pulp) and seed growth starting at full bloom and until full fruit maturity at 14 weeks after full bloom (AFB). Mesocarp fresh mass exhibited a double-sigmoidal pattern characteristic of peaches. Seed fresh mass increased to a maximum of≈1 g at 4 weeks AFB then remained unchanged during the remaining weeks of sampling. Free putrescine, spermidine, and spermine levels were significantly higher in the flower bud, declined in the mesocarp tissue during the first 2 weeks AFB, then exhibited another increase between 2 and 6 weeks AFB. In contrast, conjugated spermidine and spermine levels were low in flower buds, then increased to their maximum level at 6 weeks AFB, then declined at full fruit development. Ornithine decarboxylase (ODC, EC activity was high in flower buds (89.3 nmol·h-1·mg-1 protein) and in early stages of mesocarp development then declined to its lowest level (5.8 nmol·h-1·mg-1 protein) at full-fruit development. Arginine decarboxylase (ADC, activity did not change during the first 6 weeks of mesocarp growth but declined later, reaching its lowest (1.95 nmol·h-1·mg-1 protein) at 14 weeks AFB. During the first 5 weeks AFB, ODC activity was 3.0- to 4.5-fold that of ADC activity; however, at full-fruit maturity (14 weeks AFB) the activities of both enzymes were similar. The slowdown in mesocarp growth during pit hardening between 6 and 9 weeks AFB did not change polyamines concentrations or their biosynthetic enzymes. Free spermidine and spermine levels declined during seed development; however, between 7 and 9 weeks AFB an increase in putrescine was observed. Similarly, conjugated putrescine increased substantially during seed growth reaching its highest level of 680 nmol·g-1 fresh mass at week 8 then declined at the later weeks, while conjugated spermidine and spermine peaked at week 10 to 1,169 and 2,148 nmol·g-1 fresh mass. ODC and ADC activities declined between 3 and 5 weeks AFB. However, a significant increase in ADC but not ODC activity in the seed tissue was observed during pit hardening between 6 and 10 weeks AFB. Based on the rapid increase in putrescine and ADC activity in the seed tissue, it appears that pit hardening may be a stress-related phenomenon. Data also suggest that polyamine levels in the mesocarp and seed tissue are independently regulated.