Changes of Fruit Abscission and Carbohydrates, Hormones, Related Gene Expression in the Fruit and Pedicel of Macadamia under Starvation Stress

In order toexplore the regulation mechanism of macadamia fruitlet abscission induced by ‘starvation stress’, a treatment girdling and defoliation was applied to bearing shoots cultivar ‘H2’ at early stage fruit development, simulating starvation stress interrupting carbon supply fruit. The levels carbohydrates, hormones, related gene expression in different tissues (husk, seed, pedicel) were investigated after treatment. results showed that severe drop occurred 3~5 d contents glucose, fructose, sucrose both husk seed significantly decreased, as well fructose pedicel; this large reduction prior massive shedding. Starvation reduced GA3 ZR enhanced ABA level pedicel whereas it did not obviously change these hormones husk. After treatment, IAA content decreased considerably but increased remarkably pedicel. husk, genes sugar metabolism signaling (NI, HXK2, TPS, TPP), biosynthesis ethylene (ACO2 ACS) (NCED1.1 AAO3), upregulated stress, stress-responsive transcription factors (AP2/ERF, HD-ZIP12, bZIP124, ABI5), BG associated with accumulation auxin-responsive (Aux/IAA22 GH3.9) suppressed during period abscission. Similar changes all pedicel, except for NI AP2/ERF, which shedding downregulated drop. These suggest complicated crosstalk among sugar, IAA, may be carbohydrate starvation.