Carbohydrate Reserve Concentrations and Flower Bud Density Effects on Vegetative and Reproductive Development in Southern Highbush Blueberry

Abstract

<jats:p>Vegetative budbreak, leaf area development, and fruit size in southern highbush blueberry (<jats:italic>Vaccinium corymbosum</jats:italic> L. interspecific hybrids) decrease as flower bud density increases. The effect on fruit size has been attributed to both insufficient carbohydrate reserves and reductions in current photoassimilates caused by decreased vegetative growth. Experiments were conducted with two southern highbush blueberry cultivars, `Misty' and `Sharpblue', to test the hypothesis that increased carbohydrate reserve concentrations can overcome the detrimental effects of high flower bud density by increasing vegetative budbreak, shoot development, and whole-canopy net CO<jats:sub>2</jats:sub> exchange rate (NCER), which in turn will increase fruit size. Fully foliated plants were placed in greenhouses with either ambient (AMB) CO<jats:sub>2</jats:sub> levels (≈360 μmol·mol<jats:sup>-1</jats:sup>) or enriched (ENR) CO<jats:sub>2</jats:sub> levels (≈700 μmol·mol<jats:sup>-1</jats:sup>) for 38 d during fall. Plants were then moved outdoors, hand defoliated, and flower bud density (flower buds/cm cane length) adjusted to range from 0.07 to 0.31. Root starch and whole plant carbohydrate concentrations increased in ENR compared with AMB plants of both cultivars. Vegetative budbreak (number per centimeter cane length), leaf area, and whole-canopy NCER decreased as flower bud density increased in AMB and ENR plants of both cultivars; however, ENR `Sharpblue' plants had significantly greater vegetative growth and wholecanopy NCER at a given flower bud density compared with AMB `Sharpblue'. Concomitant with this was an increase in fruit fresh weight in ENR compared to AMB `Sharpblue'. This was not the case with `Misty', where vegetative development and fruit size were similar in ENR and AMB plants. Thus, the hypothesis that increased carbohydrate reserves will increase vegetative development and subsequent fruit size may be true only in certain cultivars of southern highbush blueberry. Alternatively, the increased carbohydrate reserve concentrations in ENR compared with AMB `Misty' plants may have been insufficient to affect subsequent vegetative or reproductive development.</jats:p>

Flower power: Floral and resource manipulations reveal how and why reproductive trade‐offs occur for lowbush blueberry (Vaccinium angustifolium)

“…Our analyses indicated that fruit ripening efficiency (as measured by ripe fruit production per node), reproductive node maintenance rate (as measured by proportion node success), and fruit dry mass content may be three traits that must decline relatively more steeply as reproductive effort increases. These results are consistent with current thoughts on resource prioritization and limitation (Brown & McNeil, ; Maust et al., ). If a plant can produce many fruit, selection may favor prioritizing the highest‐quality of these instead of equal investment across all of them (Brown & McNeil, ).…”

“…The sixth trait, ripe fruit production per node, did not increase in response to standard flower removal in this study but did increase in response to biased flower removal (Table ). Increases in vegetative mass (Hartemink et al., ; Maust et al., ), leaf area (Karlsson, Andersson, & Svensson, ; Maust et al., , ), fruit ripening rate (Maust et al., , ; Valantin‐Morison, Vaissière, Gary, & Robin, ), and fruit dry mass (Vallius, ) have all been reported in previous flower removal studies. However, we have found no studies besides ours that have reported significant removal effects on proportion node success or fruit titratable acidity.…”

“…When β 1 < 0 and β 2 > 0, the curve will be concave down, and when β 1 > 0 and β 2 < 0, the curve will be concave up. Additionally, in contrast to the quadratic‐family functions ( e.g ., Y = β 0 + β 1 X + β 2 X 2 ) used in the past to model trade‐off nonlinearity ( e.g ., Maust, Williamson, & Darnell, , ; Sletvold & Ågren, ), this exponential function is assured to be monotonic ( i.e ., continuously decreasing) as reproductive effort increases.…”

Grow Tubes Reduce Root and Crown Growth but Not Early Production during Establishment of Highbush Blueberry

“…In our study, the shoots remaining inside the dark or low light grow tube would likely have been a sink, depleting reserves in the crown and roots. Later in the season, blueberry plants export carbohydrates, from photosynthesis, to the crown and roots and carbohydrate and nitrogen reserves in the roots, crown, and older canes are important for early-season growth (Bañados et al, 2012;Maust et al, 2000).…”

Effects of Summer Pruning and Cropload on Summer and Winter Bud Carbohydrates in Sweet Cherry

“…In the period leading up to dormancy, fruit trees will accumulate total NSCs, which are then translocated into storage areas including buds, trunk, and roots (Gaudillère et al, 1992;Loescher et al, 1990). NSCs play an essential role in initiating and maintaining growth (Flore and Layne, 1999;Keller and Loescher, 1989;Maust et al, 2000;Rady and Seif El-Yazal, 2013) during periods of stress (such as dormancy, the breaking of dormancy, and initial stages of bud burst). In many fruit trees, including sweet cherry, flower buds develop earlier than vegetative buds; therefore, bud NSC reserves are critically important in initiating bud burst and must be sufficient or remobilized from other storage organs (Ben Mohamed et al, 2012;Cerasoli et al, 2004;Marafon et al, 2011;Richardson et al, 2010;Vasudevan et al, 1998) until photosynthetic leaf area can provide adequate photosassimilate to developing sinks (Dejong and Grossman, 1995;Flore and Layne, 1999).…”