Influence of photosynthetically active radiation (PAR) microclimate in the canopy of four training systems [open-center with high trunk (OH); open-center with middle trunk (OM); open-center with low trunk (OL); and a traditional round canopy (RC)] on the growth, yield and fruit quality of apple were studied in the Beijing area. The results showed that: 1) the growth and yield potential were affected by canopy light microclimate. The average leaf chlorophyll content from OH, OM and OL systems was 12.3% to 18.1% greater than that from the RC system. Trees from OH, OM, and OL systems produced 84.2% to 89.7% of shoot forming flower clusters compared to only 47.3% to 50.9% of the RC shoots. Training system did not affect total yield of 8-year-old trees, but in 10-year-old trees the RC system had lower yields compared with open-center systems. 2) Fruit quality was also affected by canopy light microclimate. The average anthocyanin content in the skin of fruit from OH, OM, and OL systems was 35.9% to 46.1% higher than that from the RC system, but chlorophyll content from the OL system was higher than in the open-center systems. Meanwhile, the contents of TSS and esters in apple flesh from the open-center systems were significantly higher than that from the RC system. 3) When the relative value of PAR in canopy exceeded 33.8%, the growth index of trees (chlorophyll: return-bloom ratio) exceeded 66.6% and the fruit quality index (TSS × anthocyanin) exceeded 94.7%. When PAR was less than 20.6%, the growth index was under 37.2% and the fruit quality index was under 67.5%. PAR value was significantly correlated with the growth and fruit quality index in the four training systems, and the total canopy volume of higher PAR(exceeding 33.8%, relative value) from OH, OM, and OL systems was 37.1% to 45.0% greater than that from the RC system.
; Tombesi et al., 2011 ; Weinbaum et al., 2001 ; Wood, 1991 , 2011b ). Plant growth regulators applied to pecan shoots affect return bloom differently, depending on whether the shoots were nonfruiting or fruiting during the treatment year ( Thompson et al
as a whole. Crane et al. (1934) suggested a positive correlation between kernel development and the number of leaves per fruit, with 8 to 10 leaves being required for optimum kernel quality. Fruit production has been shown to reduce return bloom
flowers and fruitlets chemically or by hand to increase fruit size of the current crop and encourage return bloom ( Davies, 1950 ; Wertheim, 2000 ). To increase flower bud initiation, timing of flower removal is critical; it is most effective to remove
reported for apple ( Glenn and Miller, 2005 ) and pear ( Pyrus communis L.) ( Smit et al., 2005 ). Consequently, decrease in return bloom, more likely resulting from increased fruit set, has been reported for some pear cultivars ( Smit et al., 2005
-structural carbohydrates were not related to return bloom ( Rohla et al., 2007a , 2007b ; Smith et al., 2007 ). Work on Arabidopsis indicated that a fundamental mechanism of the photoperiodic and autonomous pathways was delivery of sugar to the shoot apex ( van Nocker
) showed the effects of seeded and seedless fruit on return bloom and concluded that hormones exported from the seeds inhibit floral initiation. They showed that only the pollinated side of the parthenocarpic apple cultivar Spencer Seedless had no return
fruit in season 1, on the potential of return bloom and yield of season 2, as opposed to a carbohydrate effect. Fruit are major sources of endogenous hormones auxin and gibberellin (GA) ( Ben-Cheikh et al., 1997 ; Yuan et al., 2003 ). In “on
the 20-fruit sample and were counted and recorded. During dormancy, trunks were measured 30 cm above the graft union and number of fruit per cm 2 trunk cross-sectional area (TCSA) was calculated. The following Spring, return bloom density was
treatments on fruit weight. Return bloom was determined by selecting two limbs per tree 10 to 15 cm in diameter and then counting all blossom clusters on the tagged portion of the limb at the pink stage of flower development. Expt. 4, bloom and