The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink

Abstract

Despite the success of breeding programmes focused on increasing fruit size, relatively little is known about the anatomical and physiological changes required to increase reproductive allocation. To address this gap in knowledge, we compared fruit/ovary anatomy, vascular structure and phloem transport of two varieties of giant pumpkins, and their smaller fruited progenitor under controlled environmental conditions. We also modelled carbon transport into the fruit of competitively grown plants using data collected in the field. There was no evidence that changes in leaf area or photosynthetic capacity impacted fruit size. Instead, giant varieties differed in their ovary morphology and contained more phloem on a cross-sectional area basis in their petioles and pedicels than the ancestral variety. These results suggest that sink activity is important in determining fruit size and that giant pumpkins have an enhanced capacity to transport carbon. The strong connection observed between carbon fixation, phloem structure and fruit growth in field-grown plants indicates that breeding for large fruit has led to changes throughout the carbon transport system that could have important implications for how we think about phloem transport velocity and carbon allocation.

Growing larger with domestication: a matter of physiology, morphology or allocation?

“…; fruits Savage et al . ) has increased frequently during evolution under cultivation. Moreover, after re‐analysing the data obtained from a previous multi‐species study (Milla et al .…”

Effect of gibberellin and retardants on the germination of seeds with different types of reserve substances under the conditions of skoto- and photomorphogenesis

“…Photosynthesis is considered as a donor (source) of assimilates and growth processes as an acceptor (sink) (Yu et al, 2015;Kuryata, Polyvanyj, 2018;Kuryata, Khodanitska, 2018). These relationships in plants are regulated at different levels (Matysiak, Kaczmarek, 2013;Savage et al, 2015;Sugiura et al, 2015;Humplík et al, 2015). At the same time, there is much less information about the functioning of this system during the period of germination of bulbs, tubers, and rhizomes in the heterotrophic phase of development (Kuryata et al, 2017).…”

Bidirectional anatomical effects in a mistletoe–host relationship: Psittacanthus schiedeanus mistletoe and its hosts Liquidambar styraciflua and Quercus germana

“…5B). The diameter of sieve pores, the diameter and length of SEs are greater in parts of the plant with higher energy demands like stems and fruits in development than in other parts of the plant (Thompson, 2006; Turgeon and Wolf, 2009; Savage et al, 2015). It has been estimated that in herbaceous species, a 40% reduction in the sieve area diameter can cause up to 50% decrease in the axial conductivity of the phloem (Thompson and Wolniak, 2008).…”