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Keith A. Funnell, Errol W. Hewett, Ian J. Warrington and Julie A. Plummer

Dry matter accumulation and partitioning in plants of Zantedeschia Spreng. `Best Gold' aff. Z. pentlandii (Wats.) Wittm. (syn. Richardia pentlandii Wats.) were quantified under a range of temperature and photosynthetic photon flux (PPF) regimes using plant growth analysis. The relative rate of dry matter accumulation [relative growth rate (RGRM), g·g-1·d-1] was highly correlated with the partitioning of the daily increment of dry matter into leaf tissue [leaf matter partitioning (LMP), g·d-1 per g·d-1]. In contrast, a poor correlation existed between RGRM and net assimilation rate (NAR, g·m-2·d-1). Maximum values of RGRM increased linearly with increasing temperature (from 13 to 28 °C), with a base temperature of 2.1 ± 2.7 °C. The optimum temperature for growth was PPF dependent with maximum total plant dry mass occurring under high PPF (694 μmol·m-2·s-1) at 25 °C. However, as the plant responded to PPF by altering LMP, final total plant dry mass was actually greater under the low PPF regime (348 μmol·m-2·s-1) at temperatures <22 °C. The optimum temperature for dry matter accumulation was close to the average daily air temperature during the growing season for the natural habitat of the parent species. Similarly, the greater dry matter accumulation under the combination of either low PPF and cooler temperatures or high PPF and warmer temperatures was paralleled by the diversity of PPF habitats in the natural open grassland and forest margin the parent species occupies. It is therefore suggested that Zantedeschia `Best Gold' is well adapted to optimize growth under these environmental conditions.

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John C. Beaulieu and Dyremple B. Marsh

A greenhouse experiment was conducted to examine the relationship between tissue B concentration and dry matter accumulation in broccoli. `Pirate ' was grown in fine silica sand and supplied nutrient solutions containing 0.2, 0.8, 1.4, 2.0, 2.6, 3.2, 3.8, and 4.4 mg·liter-1 B. Plants were sampled for the 5th, 10th, and 15th fully expanded mature leaf, and plant material was collected' for dry matter measurement and boron analysis at each growth stage. The lowest specific leaf weights for the 5th, 10th, and 15th leaves were obtained with the 4.4 mg·liter-1 treatment. At maturity, leaf, petiole stalk, and shoot dry weights were lowest at 4.4 mg·liter-1 B. Treatments supplying less than 3.2 mg· liter-1 B, resulted in a notable decrease in tissue B concentrations from the 5th to the 15th leaf. There was a linear increase' in B concentration in all leaf tissue samples as B treatment increased. At maturity, optimum B concentrations of 531.5, 73.7, 29.8, and 64.6 mg·g-1 were found for the lamina, petiole, stalk, and head, respectively. These concentrations occurred in plants receiving treatment levels of 2.0-3.8 mg·liter-1 B.

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S.J. McArtney and D.C. Ferree

Dormant, 2-year-old, own-rooted `Chambourcin' grapevines (Vitis sp.) were subjected to two levels of root pruning (none, two-thirds roots removed) and were subsequently trained with either one or two canes. Vines were destructively harvested at bloom and after harvest when dormant to determine the effect of stored reserves in the root and competition between shoots for these reserves on vine growth and berry development. Removing 78% of the root system reduced shoot elongation and leaf area more effectively than did increasing the number of shoots per vine from one to two. Root pruning reduced the elongation rate of shoots for 45 days after budbreak, whereas increasing the shoot number reduced the shoot elongation rate for only 20 days after budbreak. A positive linear relationship was observed between leaf area per shoot at bloom and the number of berries per single cluster. These results demonstrate the importance of 1) the roots as a source of reserves for the initial development of vegetative tissues in spring, and 2) the rapid development of leaf area on an individual shoot for high set of grape berries on that shoot.

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Muntubani D.S. Nzima, George C. Martin and Chic Nishijima

We investigated the development of leaf area (LA) and the distribution of dry matter within branches of 25-year-old, alternate-bearing `Kerman' pistachio (Pistacia vera L.) trees that were in their natural “on” (heavy) or “off” (light) bearing cycles to determine the immediate and delayed effects of fruiting on shoot growth. Compared to “off” trees, individual leaves of “on” trees were greater in number and expanded twice as fast during the first 30 days after full bloom (FB) (FB + 30). Mature, fully expanded leaves of “on” trees were smaller (124.1±3.26 cm2) than those from “off” tree (163.3±3.40 cm2), indicating delayed demands of fruiting on initial leaf growth. Total LA per current shoot was greater in “on” than “off” trees because shoots of “on” trees averaged eight leaves, compared with six for “off” trees. More inflorescence buds per shoot (seven vs. three buds) abscised from “on” than from “off” trees. About 60% of the young developing nuts had abscised by FB + 30 when they weighed <250 mg each and another 25% abscised between FB + 30 and FB + 60 when individual nuts weighed ≈400 mg. The average total dry mass (DM) of individual branches of “on” trees increased 1322% (5·9 to 83·9 g) compared to 598% (4·2 to 29·3 g) in “off” trees. Besides nuts, leaves accumulated the greatest amount of dry matter within individual branches followed in decreasing order by current wood, 1-year-old wood, and inflorescence buds. DMs of individual leaves of “on” trees averaged between 15% and 48% greater than leaves of “off” trees. “Off” trees invested 4.6 g of dry matter into individual 1-year-old wood and 2.1 g into current wood. “On” trees, however, invested 1.3 g of dry matter into 1-year-old wood and 4.3 g of dry matter into current wood. One-year-old wood was an important major source of carbohydrates for developing leaves, current wood, rachises, and nuts. The immediate demands of fruiting on individual components of a branch were measured as losses in DMs. Individual leaves, current wood, 1-year wood, and rachises lost 1.1%, 0.3%, 1.1%, and 1.0%, respectively, of the average total DMs of individual branches of “on” trees. This loss was equivalent to 5.7%, 5.9%, 26.7%, and 16.4%, respectively, of the seasonal average peak DMs of the respective individual components of the branch.

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Guohai Xia, Lailiang Cheng, Alan Lakso and Martin Goffinet

The objective of this study was to determine how nitrogen (N) supply affects the source-sink balance and fruit size of ‘Gala’ apple when crop load was controlled at a moderate level. Five-year-old ‘Gala’/‘M.26’ trees grown in sand culture and trained in tall spindle received a total of 3.3, 10.0, 20.0, or 40.0 g actual N through fertigation using Hoagland's solution from bloom to 3 weeks before harvest. The crop load of these trees was adjusted to 6.5 fruit/cm2 trunk cross-sectional area by hand thinning when the diameter of the largest fruit was 10 mm. As N supply increased, total shoot leaf area in the canopy increased, whereas total spur leaf area remained unchanged. Both single leaf and whole canopy net CO2 assimilation rates increased with increasing N supply. The net dry matter gain of the whole tree from budbreak to fruit harvest increased ≈74% from the lowest N supply to the highest N supply, but the proportion of net dry matter gain partitioned to fruit (harvest index) decreased from 83% to 70%. Both leaf area to fruit ratio and average final fruit size increased with increasing N supply, and a linear relationship was found between leaf area to fruit ratio and final fruit size. The number of cells per fruit increased with increasing N supply, whereas average cell size remained unchanged. As N supply increased, fruit soluble solids concentration increased, whereas fruit firmness decreased slightly. These results indicate that 1) apple trees grown under low N supply are source-limited; and 2) within the range of N supply used, increasing N supply improves leaf N status, leaf and whole tree photosynthetic capacity, and leaf area to fruit ratio, leading to more cells per fruit, larger fruit, and higher soluble solids.

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Shinsuke Agehara and Daniel I. Leskovar

–C ). Inhibitory effects of ABA on shoot dry matter accumulation were rapid and transient in ‘Florida 91’, decreasing shoot dry weight by 7% at 0 DBM (184 vs. 171 mg), whereas they became gradually significant in ‘Mariana’, decreasing shoot dry weight by 8% at 14

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Laban K. Rutto, Myong-Sook Ansari and Michael Brandt

.0353 oz, 1 g·m −2 = 0.0033 oz/ft 2 . Discussion In this study, we found that dry matter accumulation is correlated with mineral nutrition in stinging nettle. There was a positive correlation between biomass yield and N availability, and an inverse

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Christopher Vincent, Diane Rowland and Bruce Schaffer

plants; 2) stress memory improves papaya drought tolerance, defined as maintenance of dry matter accumulation or A during water deficits; and 3) PA-induced stress memory diminishes over time. Materials and Methods Plant material. ‘Red Lady’ papaya seeds

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How-Chiun Wu and Chun-Chih Lin

. (1989) suggested that the presence of sucrose in the growth medium could affect the time course required for cultures to achieve a positive CO 2 balance and photosynthetic dry matter accumulation. This may explain the enhanced survival of plantlets

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Francesco Montesano and Marc W. van Iersel

active leaf area were more important for dry matter accumulation than were differences in the photosynthetic rate per unit leaf area. Schwarz et al. (2002) affirmed that single-leaf photosynthesis measurements are poor indicators of plant growth