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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 4.1.1.17) 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, 4.1.1.19) 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.

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Martin P.N. Gent and Richard J. McAvoy

from PSEFW. Water stress may be used to control plant growth and quality. A constant low volumetric water content can control both biomass and height growth of ornamental plants ( Burnett et al., 2005 ; Van Iersel et al., 2004), although the extent of

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B. Tisserat and S.F. Vaughn

The growth (fresh weight), morphogenesis (number of needles and roots and shoot length) and monoterpene (α- and β-pinene) levels were determined in Pinus taeda L. (loblolly pine) seedlings exposed to 350, 1,500, 3,000, 10,000, or 30,000 μmol·mol-1 CO2 for 30 days under greenhouse conditions. Seedlings exposed to ultra-high levels (i.e., ≥3000 μmol·mol-1 CO2) had significantly higher (P = 0.05) fresh weight, needle number, root number, and shoot lengths compared to seedlings grown under ambient air (350 μmol·mol-1 CO2). Seedling fresh weights, number of roots, shoot length, and number of needles from pine seedlings supplemented with 10,000 μmol·mol-1 CO2 increased 341%, 200%, 74%, and 75 %, respectively, when compared to seedlings grown without any CO2 enrichment. In addition, α- and β-pinene levels in seedlings increased under ultra-high CO2 levels. The dominant monoterpene, α-pinene, increased 57% in seedlings grown under 10,000 μmol·mol-1 CO2 compared to levels obtained under 350 μmol·mol-1 CO2.

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Scott Henderson, David Gholami, and Youbin Zheng

a crop. When this variation in water usage is not accounted for when irrigating, areas of under- and over-watering may develop, which can reduce plant growth through drought ( Gindaba et al., 2005 ) or flooding stress ( Olivella et al., 2000 ). Many

Open access

Nianwei Qiu, Li Tian, Xifeng Yan, Haoyu Dong, Mengyu Zhang, Guoliang Han, and Feng Zhou

et al., 2016 ). Therefore, strontium at high concentrations has inhibitive effects on plants. Although strontium is not an essential nutrient element for plants, we have recently confirmed that strontium at low concentrations can promote the growth

Open access

Fengyun Zhao, Yu Jiang, Xiufeng He, Huaifeng Liu, and Kun Yu

organic fertilizer and decreasing drip chemical fertilizer in grape production. Therefore, we aimed to study the effects of increasing organic fertilizer and decreasing drip chemical fertilizer on the tree growth and fruit quality of grapes in arid areas

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R. Paul Schreiner and Jungmin Lee

relatively small surface area of the pots (20% of the vineyard floor surface area) intercepts little rainfall ( Schreiner et al., 2013 ). This article reports the impact of a post-véraison water deficit on vine growth, yield, and nutrient status in leaves and

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Sylvie Jenni, Katrine A. Stewart, Gaétan Bourgeois, and Daniel C. Cloutier

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Wallace G. Pill

Growth Media