A biophysical model of kiwifruit (Actinidia deliciosa) berry development.

Alistair J Hall,Michael J Clearwater,Peter E H Minchin,Michel Génard

doi:10.1093/jxb/ert317

Alistair J Hall, Michael J Clearwater + Show 2 more

Open Access

https://doi.org/10.1093/jxb/ert317

Copy DOI

Abstract

A model of kiwifruit berry development is presented, building on the model of Fishman and Génard used for peach fruit. That model has been extended to incorporate a number of important features of kiwifruit growth. First, the kiwifruit berry is attached to the stem through a pedicel/receptacle complex which contributes significantly to the hydraulic resistance between the stem and the fruit, and this resistance changes considerably during the season. Second, much of the carbohydrate in kiwifruit berries is stored as starch until the fruit matures late in the season, when the starch hydrolyses to soluble sugars. This starch storage has a major effect on the osmotic potential of the fruit, so an existing model of kiwifruit starch dynamics was included in the model. Using previously published approaches, we also included elasticity and extended the modelling period to cover both the cell division and cell expansion phases of growth. The resulting model showed close simulation of field observations of fresh weight, dry matter, starch, and soluble solids in kiwifruit. Comparison with continuous measurements of fruit diameter confirmed that elasticity was needed to adequately simulate observed diurnal variation in fruit size. Sensitivity analyses suggested that the model is particularly sensitive to variation in inputs relating to water (stem water potential and the humidity of the air), and to parameters controlling cell expansion (cell wall extensibility). Some limitations in the model structure were identified, suggesting that a revised model including current apoplastic/symplastic concepts needs to be developed.

Highlights

Fruit growth involves both phloem and xylem flow, transpiration from the fruit surface, and the internal processes of cell division, differentiation, metabolism, and catabolism
The aim of this study was to develop a physiological model of fruit development of kiwifruit, capable of Abbreviations: DAFB, days after full bloom; LVDT, linear voltage displacement transducer
Import into the fruit from the xylem is proportional to the difference in water potentials, while mass flow from the phloem includes a reflection coefficient to include a component of symplastic flow

Summary

Introduction

Fruit growth involves both phloem and xylem flow, transpiration from the fruit surface, and the internal processes of cell division, differentiation, metabolism, and catabolism. Final fruit size and composition are a result of the coupled import of water and carbon during growth. Carbohydrate, usually sucrose, arriving in the phloem is the major substrate for growth and storage, but is osmotically active, thereby influencing phloem flow into the fruit. Inter-conversions in the chemical form and location of solutes impact on the fruit water balance and growth via osmotic interactions. The external environment affects fruit transpiration as well as the phloem and xylem flows, so affects fruit size as well as fruit composition. A process-based model of fruit growth is needed to provide integration of the known chemical and physical processes involved

Objectives

Methods

Results

Conclusion