The cotton growth was impaired by the decrease of carbohydrate translocation due to the alteration of the pedicel structure ( de Oliveira et al., 2006).

Other lines of evidence demonstrated the correlation between pedicel diameter and fruit size at harvest ( Bustan et al., 1995 Nii, 1998), and it has been proposed that the pear fruit adjusted the development of the vascular bundle of the pedicel as the fruit grew from the young to mature stage ( Nii, 1980). In another study of fruit pedicel, the Ca content in the phloem was even higher than that in the xylem during the fruit growth, such as litchi, indicative of possible Ca delivery to fruit also via phloem mass flow ( Song W. In a study with nine fruit species, vessel density, size, and area in the pedicel showed quite variations among them, but the loss of xylem functionality along with the fruit maturity and higher Ca content in the pedicel than the fruit were found as universal patterns, indicating the existence of a pedicel-fruit “bottleneck” effect in Ca transport across species ( Song W. Therefore, the structural properties of both xylem and phloem of the pedicel are important in affecting the fruit growth. Mineral elements present in soil enter the root apoplast path and are transported along with the mass flow of water to the fruit through the xylem pathway ( Gilliham et al., 2011), while the photosynthate is delivered to the fruit via the phloem pathway. In the early stage of the fruit growth, water enters the fruit predominantly via the xylem ( Greenspan et al., 1994, 1996) and thereafter mainly through the phloem as the xylem function slows down gradually along with the development of the fruit ( Bondada et al., 2005). Therefore, the fruit characteristics are highly affected by the efficiency of water and nutrient transport via the pedicel, which is determined by the structural properties of the pedicel.

In fruit trees, the pedicel is a bridge linking the parent tree and the fruit, through which the water, mineral nutrients, and photosynthate are transported to the fruit. Our findings provided direct evidence that pedicel structural elements contributed distinctively to the fruit characteristics among pear species. The porosity, the ratio of the surface area to the volume, and the spatial arrangement of the vessels showed significant variations across the pear species, indicating the distinction of the hydraulic conductance of the pedicels. Pedicel elements, including pith, fiber, and cortex, likely play a certain role in the fruit growth due to the variations of their characteristics demonstrated in the four pear species. The fruit size positively correlated with pedicel length, fiber area, pedicel diameter, the area percentage of the cortex, and the area percentage of phloem however, fruit firmness and soluble solids concentration are showed a stronger positive correlation with xylem area, pith area, the area percentage of xylem, the area percentage of sieve tube, and the area percentage of pith. The European pear (Conference) showed distinct fruit shape index and pedicel structural properties compared with the oriental pears (Akizuki, Yali, and Nanguoli). Combining the investigation of fruit characteristics, the statistical analysis of the pedicel structural properties, and the 2D and 3D anatomical observation of the pedicel, this study found distinctive contributions of the pedicel elements to the fruit characteristics in four pear species. The genetic specificity determines the characteristics of the pedicel and the fruit, but the relationship between the pedicel structure and the fruit characteristics is unexplored.

Fruit pedicel is the bridge linking the parent tree and the fruit, which is an important channel for water and nutrients transport to the fruit.

Chinese pear shaped vessel meaning