Abstract Detail

Anatomy and Morphology

Barceló-Anguiano, M [1], Hormaza, Jose [2], Losada, Juan M [3].

SOURCE-SINK TRANSPORT IN POLYPLOID TREES: A CASE EXAMPLE IN AUTOTETRAPLOID MANGO (Mangifera indica).

The relationship between ploidy and functional anatomy in trees has been traditionally studied from the perspective of the xylem, leaving fragmentary information on the physiology of the phloem along the plant. This is partly explained by the fact that the generation of polyploid trees from genome duplication of a single genotype is difficult to obtain naturally. However, such autopolyploid individuals have been developed in different species, such as mangoes. Here we explore the relationship between vascular cell size and ploidy using a diploid genotype and a tetraploid genotype generated by genome duplication of the diploid genotype. We performed physiological, anatomical, and molecular biology analysis of leaves, stems, and inflorescences of the diploid and tetraploid mango trees to understand the relationship between ploidy and vascular performance in trees. Under similar growth conditions, diploid and tetraploid clonally propagated trees displayed similar photosynthetic performance, but the transpiration rates were lower in tetraploids, suggesting better use of water resources that may correlate with the higher stomatal size of tetraploids. While water potential was similar in both cytotypes, bench experiments studying leaf dehydration showed better water retention by the tetraploid trees. Autotetraploid mangos showed overall larger cell sizes in their vascular elements, including the vessel elements of the xylem, and the sieve tube elements of the phloem in stems and inflorescences, but these differences were larger in the major veins of the leaves. A specific epitope that characterized the cell walls of the sieve tube elements of the phloem was further localized specifically in the subsidiary cells bordering stomata, suggesting common mechanical properties. Our study implies one of the first proof of concept that shows how autopolyploid trees develop an enhanced vascular function with respect to their diploid original genotype. The resistance of the two parallel vascular conduits correlates with the Hagen-Poiseulle model of fluid transport from source (leaves) to sink (inflorescences or roots). This resistance increases toward the inflorescences, and it is attenuated in tetraploids, resulting in bigger flowers compared to diploids. Altogether, these results emphasize the increase of vascular cell size in polyploid trees which could be a mechanism to improve tolerance to abiotic stresses, such as lower water availability.

1 - Spanish Superior Research Council, Subtropical and Mediterranean Fruticulture, Avda Dr. Wienberg s/n, Algarrobo-Costa, Malaga, 29750, Spain
2 - IHSM La Mayora - CSIC, Subtropical Fruits, Finca La Mayora S/N, Algarrobo-Costa, 29750, Spain
3 - Spanish Superior Research Council, Subtropical Hortrofruticulture, Avda. Dr. Wienberg, Algarrobo-Costa, MA, 29750, Spain

Keywords:
Phloem
xylem
polyploidy
vascular system
mangifera indica.

Presentation Type: Oral Paper
Session: AM1, Anatomy and Morphology
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 10:30 AM
Number: AM1003
Abstract ID:545
Candidate for Awards:Katherine Esau Award