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  • Author or Editor: J.G. Streeter x
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Container-grown `Chambourcin' grapevines were exposed to soil compaction created by changing soil bulk density to determine the effect of levels of compaction, rootstocks and moisture stress on mineral nutrition, leaf gas exchange and foliar carbohydrate levels. Shoot growth, leaf area, number of inflorescences and leaf dry weight decreased linearly as soil bulk density increased with the effects being significant above 1.4 g·cm-3. The early season leaf area was reduced 40% in the second season, but later leaves were unaffected by a soil bulk density of 1.5 g·cm-3. Net photosynthesis (Pn) and transpiration (E) increased linearly with increasing soil bulk density the first year, but the second year a nonlinear pattern was observed with highest rates at 1.3 and 1.4 g·cm-3. Soil bulk density of 1.5 g·cm-3 reduced number of leaves, leaf area and shoot length and advanced bloom 16 days on `Chambourcin' vines on six rootstocks with no interaction of rootstock and soil compaction. Withholding water for 8 days reduced Pn and E in all treatments, with no effect on shoot length, leaf, stem and total dry weights. Moisture stress in the noncompacted soil caused a reduction in leaf concentration of fructose, glucose and myo-inositol, but moisture stress had no effect in the compacted soil. Moisture stress caused a reduction in sucrose in both compacted and noncompacted soil. Compacting soil to a bulk density of 1.5 g·cm-3 was associated with an increase in leaf N, Ca, Mg, Al, Fe, Mn, Na, and Zn and a decrease in P, K, B, and Mo.

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Glucosinolates are secondary plant products of the Brassicaceae that may influence vegetable flavor and human health. Soil moisture levels and plant water status are thought to influence cabbage head glucosinolate levels. However, no information is available on the effect of irrigation timing relative to plant developmental stage on glucosinolate concentrations in cabbage. To address these gaps in the literature, cabbage (cv. Bravo) was grown in 2002 and 2003 at The Ohio State Univ., Ohio Agricultural Research and development Center in Wooster, Ohio. The four irrigation treatments, arranged in a RCB design, were: 1) irrigation throughout development [no stress (NS)], 2) irrigation only during head development [frame stress (FS)], 3) irrigation only during frame development [head stress (HS)], and 4) no irrigation [frame and head stress (FHS)]. Irrigation was supplied via drip tape and scheduled by the hand-feel method. Differential soil moisture levels among treatments were confirmed with gypsum block, time domain reflectometry (TDR) and gravimetric measurements. Analyzed across years, irrigation timing significantly affected total glucosinolate concentrations, with levels 36% greater in cabbage not irrigated during head development (HS, FHS) relative to cabbage receiving irrigation during head development (NS, FS). Concentrations were highest (29.4 mmol·kg-1) and lowest (19.4 mmol·kg-1) in FHS and FS cabbage, respectively. Irrigation effects were greater in 2002, when air temperatures were higher and rainfall and relative humidity lower than in 2003. We conclude from the data that head development is the critical stage at which irrigation should be applied in order to influence cabbage glucosinolate levels at maturity.

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Container-grown apple (Malus ×domestica Borkh.) trees were exposed to soil compaction created by changing soil bulk density (SBD) to determine the effect of compaction levels, rootstock, and moisture stress on mineral nutrition, leaf gas exchange, and foliar carbohydrate levels. With SBD of 1.0, 1.2, and 1.4 g·cm-3, there was no interaction of rootstock and soil compaction for growth of `Melrose' trees on nine rootstocks. Trees grown in a SBD of 1.2 g·cm-3 had a greater dry weight than trees at 1.4 g·cm-3 bulk density. Increasing SBD to 1.5 g·cm-3 reduced shoot length, total leaf area, leaf size, and dry weight of leaves, shoots, and roots. The interaction between rootstock and SBD was significant and total dry weight of `B.9', `G.16', `G.30', and `M.7 EMLA' was less influenced by 1.5 g·cm-3 soil than trees on `M.26 EMLA' and `MM.106 EMLA'. Withholding moisture for 10 days at the end of a 70-day experiment caused 8% to 25% reduction in growth in a non-compacted (1.0 g·cm-3) soil with much less effect in a compacted soil. Prior to imposing the moisture stress by withholding water, net photosynthesis (Pn) was reduced 13% and transpiration (E) 19% by increasing bulk density to 1.5 g·cm-3. Following 7 days of moisture stress in non-compacted soil, Pn and E were reduced 49% and 36%, respectively, with no such reductions in the compacted soil. Increasing SBD to 1.5 g·cm-3 caused a decrease in the leaf concentration of quinic acid, myoinositol, and sucrose and an increase in fructose and glucose. Trees growing in 1.5 g·cm-3 had reduced concentrations of N, Ca, Mg, Mn, Na, and Zn, and increased P, K, B, and Fe in leaves.

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To better understand the influence of environmental factors on components of crop productivity and nutritional and sensory quality parameters, the fresh-market cabbage (Brassica oleracea L. Capitata Group) `Bravo' was irrigated at different periods relative to head development in 2002 and 2003 at the Ohio Agricultural Research and Development Center in Wooster. Irrigation was provided to plots either: 1) from planting to maturity, 2) during frame development only, or 3) during head development only. Control plants received no irrigation after plant establishment. Irrigation timing relative to crop stage significantly affected all head characteristics with the greatest differences between cabbage receiving irrigation during head development and cabbage not irrigated during head development. On average, heads from cabbage irrigated during head development were heavier, larger, less pointed, and had less volume occupied by the core than heads from cabbage not irrigated during head development. A positive, linear relationship (r 2 = 0.89) was found between head volume and head weight. Across years, combined head fructose and glucose concentrations were significantly greater and sucrose concentrations significantly lower in cabbage receiving irrigation during head development than in cabbage not irrigated during head development. Total and individual glucosinolate levels were greater in cabbage not irrigated during head development relative to cabbage receiving irrigation during head development. Head weight, fructose and glucose were positively related to the proportion of estimated crop evapotranspiration replaced by irrigation during head development, while the opposite response was observed in head sucrose and total and indole glucosinolate concentrations.

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Clarifying the influence of abiotic environmental factors on the glucosinolate-myrosinase complex in vegetables of the Brassicaceae is an important step in understanding physiological processes that affect crop quality. Previous related work in this lab has shown that irrigation timing in the field may influence physical-, chemical- and sensory-based indicators of cabbage quality. The objective of this study was to record glucosinolate concentrations and myrosinase activity in crop tissues from plants subjected to varying soil moisture levels, employing radish as a model. Plants of cv. Belle Glade were grown in a controlled environment system designed at the Ohio Agricultural Research and Development Center in Wooster, Ohio for maintenance of target soil moisture levels. Pots were maintained at three soil moisture ranges, 40% to 60% (A), 20% to 30% (B) and 10% to 20% (C) volumetric soil moisture content at 30 °C. Preliminary observations revealed that treatments A, B and C corresponded to soil tensions which were not stressful, moderately stressful, and severely stressful to plants, respectively. Pot evapotranspiration, leaf stomatal conductance and plant size followed the order A>B>C, while canopy temperatures followed the order C>B>A. In leaves, glucosinolate concentrations and myrosinase activity were about 15% greater in treatments B and C than in A, while glucosinolate levels and myrosinase activity were 28 and 50% lower in hypocotyls and roots, respectively, in C than in A. It is hypothesized that changes in enzyme and substrate synthesis and translocation within the plant in response to sub-optimal soil moisture levels may explain the differential response of tissue glucosinolate concentrations and myrosinase activity to soil moisture treatments.

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Cabbage (cv. Bravo) was grown in 2002 and 2003 at The Ohio State Univ., Ohio Agricultural Research and development Center in Wooster, Ohio. The four irrigation treatments, arranged in a RCB design, were: 1) irrigation throughout development [no stress (NS)], 2) irrigation only during head development [frame stress (FS)], 3) irrigation only during frame development [head stress (HS)], and 4) no irrigation [frame and head stress (FHS)]. Irrigation timing relative to crop stage significantly affected all head characteristics except density, with the greatest differences between cabbage receiving irrigation during head development (NS, FS) and cabbage not irrigated during head development (FHS, HS). On average, heads from NS and FS plots were heavier (38%), larger (15%), less pointed and had less volume occupied by the core than heads from HS and FHS plots. Combined head fructose and glucose concentrations were significantly greater in cabbage receiving irrigation during head development than in cabbage not irrigated during head development (47% vs. 41% dwt, respectively). Sucrose concentrations were significantly greater in cabbage not irrigated during head development than cabbage receiving irrigation during head development (8% vs. 6% dwt, respectively). The higher ratio of sucrose: fructose+glucose observed in HS and FHS relative to NS and FS treatments was interpreted as an osmo-regulatory response with potential implications for cabbage flavor. Overall, it was concluded that physiological responses elicited in cabbage by differential irrigation can affect important head traits, and that targeted applications of water during specific stages of crop development may be utilized to maximize water use efficiency and crop quality.

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Glucosinolates are secondary plant metabolites derived from amino acids and they influence human health, pest populations and crop flavor. Our primary objective was to determine the independent and interactive effects of planting date (PD) and cultivar (C) on total glucosinolate concentrations in cabbage, in part to help develop management systems that optimize them. A second objective was to explore the reported link between total glucosinolate concentrations and pungency in fresh cabbage. Six commercial fresh market cabbage cultivars were planted in May and June 2001 and 2002 at the Ohio Agricultural Research and Development Center (OARDC) Vegetable Crops Research Branch in Fremont, Ohio. Total glucosinolate concentrations in horticulturally mature heads were determined using a glucose evolution procedure. In 2001, 12 to 14 experienced panelists also scored sample pungency. Total glucosinolate concentrations were significantly affected by PD and C, but the PD × C interaction was not significant. Mean glucosinolate concentrations were greater in Maythan June-planted cabbage in both years. Cultivar ranking with regard to glucosinolate concentrations was similar between planting dates in both years. `Cheers' had the highest mean glucosinolate concentrations (23.1 and 29.5 mmol·kg-1 dry weight in 2001 and 2002, respectively) and `Solid Blue 790' the lowest (17.1 and 19.7 mmol·kg-1 dry weight in 2001 and 2002, respectively). In 2001, panelists generally scored cultivars highest in glucosinolates as more pungent than cultivars lowest in glucosinolates. These data suggest that planting date and cultivar effects on total glucosinolate concentrations in cabbage are largely independent. Climatic data suggest that higher air temperatures during head development of May-compared to June-planted cabbage induced plant stress and resulted in higher glucosinolate concentrations in May-planted cabbage.

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