Abstract
Calcium (Ca) deficiency in fruit causes various physiological disorders leading to quality loss. However, disorders related to Ca deficiency are not simply caused by a shortage of calcium supply. Ca distribution is also an important relation. This study examined Ca distribution pattern in fruit and pedicel in litchi (Litchi chinensis Sonn.) and the influence of Ca channel inhibitor La3+ on fruit Ca uptake and distribution. In situ distribution of Ca in the phloem and xylem tissues of the pedicel was visualized by Ca mapping with X-ray microanalyzer. Ca2+ analogy Sr2+ was used to trace Ca2+ transport pathway to fruit as well as distribution pattern. The results showed Ca was more distributed in the pericarp, especially the distal part. Ca level in the bark/phloem was always significantly higher than in the xylem and increased with stem age, suggesting constant influx of Ca into the phloem from the xylem. La3+ increased the ratio of Ca in the xylem to that in the bark in the pedicel and significantly reduced Ca accumulation by 55.6% in fruit, suggesting influx of Ca into the symplast was involved in fruit Ca uptake. Sr2+ introduced from fruit stalk was found to be transported to fruit through the phloem as Sr was largely distributed in the phloem, and fruit stalk girdling significantly reduced Sr accumulation in the pericarp. Ca mapping across the pedicel revealed Ca-rich sites in the parenchyma cells in the phloem and along the cambium, where abundant Ca oxalate crystals were found. The results suggested extensive influx of Ca from xylem/apoplast pathway into the phloem/symplast pathway in the pedicel, which enables phloem/symplast pathway to contribute a considerable part to Ca uptake in litchi fruit.
Highlights
Calcium (Ca) is one of the essential nutrients in plants, serving as an important element for cell wall construction and membrane stabilization, as an intracellular messenger for signaling and regulations, and as a counter ion for organic acids (White and Broadley, 2003; Hepler, 2005)
Jones et al (1983) found great difference between estimated calcium accumulation based on vessel influx volume and calcium concentration and measured calcium accumulation in apple fruit, indicating phloem might be a major pathway for calcium transport
The fruit samples were sectioned into the top pericarp, the middle pericarp, the basal pericarp, fruit base, calyx ring (C), and 5-mm segments of fruit stalk, which were indicated by S1, S2, S3, and S4 according to their distance from the calyx ring (Figure 1)
Summary
Calcium (Ca) is one of the essential nutrients in plants, serving as an important element for cell wall construction and membrane stabilization, as an intracellular messenger for signaling and regulations, and as a counter ion for organic acids (White and Broadley, 2003; Hepler, 2005). Bark ( phloem and cortex) and wood (xylem tissue) from the limbs (>6 cm diameter), large branches (4 cm diameter), small branches (2 cm diameter), shoots (0.8 cm diameter), and fruit stalks, as well as the entire pericarp, were separately collected at 76 DAA, when fruit were fully matured.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
