The relationship between basipetal auxin transport and calcium allocation in vegetative and reproductive flushes in avocado

Abstract

Indole-3-acetic acid (IAA) export and 45Ca uptake by excised avocado flower, fruitlet and shoots from the vegetative flush were determined in conditions which limited transpiration flow to a minimum. Treatments using auxin transport inhibitors were included to ascertain if IAA played a role in the allocation of Ca. IAA levels were determined using radioimmunoassay. IAA export and ~Ca uptake were strongest for the vegetative flush and weaker for the reproductive structures for the first 5 weeks after flowering. The competition for and control of Ca partitioning is discussed.

Fruit calcium accumulation coupled and uncoupled from its transpiration in kiwifruit

“…For example, the 'metabolic Ca demand' and the chemical aspects of the conductive tissues (e.g. adsorption and desorption along the walls of the xylem pathway) and the mutual relationship between polar basipetal auxin transport and acropetal Ca transport (Stahly and Benson, 1970;Bangerth, 1976Bangerth, , 1979Banuelos et al, 1987;Cutting and Bower, 1989;Pomper and Grusak, 1997;McLaughlin and Wimmer, 1999). Also the action of specialised transfer cells and the higher expression of Ca transporters and Ca binding proteins may promote accumulation of Ca into fruit independently of its transpiration (Pate and Gunning, 1972;Park et al, 2005).…”

“…since most suffer Ca deficiency disorders (Cutting and Bower, 1989;Ferguson and Watkins, 1989;Witney et al, 1990;Saure, 1996;Ho and White, 2005) and grow in changing environments with variable VPD. Results could open up the reinterpretation of certain techniques suggested at field scale to improve fruit quality.…”

“…apple, avocado, tomato, grape) including kiwifruit suffers physiological disorders during storage and, sometimes, also pre-harvest. Such disorders can be associated with low calcium (Ca) content (Saure, 1996;Ferguson and Watkins, 1989;Cutting and Bower, 1989;Witney et al, 1990;Ho and White, 2005;Thorp et al, 2003;Ferguson et al, 2003;Ciccarese et al, 2013).…”

Fruit Transpiration: Mechanisms and Significance for Fruit Nutrition and Growth

“…Calcium delivery to fruit has also been associated to hormonal activities. For example, a mutual relationship between polar basipetal auxin transport and acropetal Ca transport has been reported for tomato, apple and avocado (Stahly and Benson, 1970;Bangerth, 1976;Banuelos et al 1987;Cutting and Bower, 1989). However, there is still limited information to discriminate (and quantify) the effect of these transpirationindependent stimuli in Ca nutrition.…”

“…Calcium movement in plants has been extensively studied in relation to factors such as transpiration flux, hormonal activities, nutrient demand and chemical properties of the conductive system (Bangerth, 1979;Banuelos et al, 1987;Cutting and Bower, 1989;McLaughlin and Wimmer, 1999), however information is still limited to discriminate the relative prominence of each individual factor. Our data were insufficient to indicate the transpiration-independent mechanism(s) by which 45% of the Ca concentration accrued under high humidity condition, but the hormones were possibly involved.…”