Hydraulic resistance of developing Actinidia fruit

Area of Science:

• Plant Physiology
• Fruit Development
• Xylem Biology

Background:

• Xylem flow to fruits typically declines during development, affecting nutrient and carbohydrate accumulation.
• Increased xylem hydraulic resistance (RT) is hypothesized to cause this decline.

Purpose of the Study:

• To investigate developmental changes in kiwifruit berry RT.
• To pinpoint the fruit region responsible for RT changes.
• To assess the impact of reduced irradiance on RT and mineral accumulation.

Main Methods:

• Measured RT using pressure chamber and flow meter methods.
• Partitioned RT across fruit tissues (pedicel, receptacle, berry).
• Used dye tracers and artificial shading to study xylem function and light effects.

Main Results:

• RT initially decreased then increased during fruit development, with major changes in the receptacle.
• Dye transport ceased beyond the receptacle later in development.
• Shading increased RT, reduced dye movement, and lowered calcium concentration.

Conclusions:

• Increased receptacle RT correlates with slowed growth, reduced transpiration, and starch accumulation.
• Developmental RT changes may link to phloem function and water potential gradients.
• Shading impacts fruit vascular development and nutrient transport independently of transpiration.