Influence of Leaf Water Potential and Defoliation Techniques on Leaf Area Characteristics in 'Merlot'/41B Grapevines

This study aimed to assess how variations in leaf water potential and
different defoliation treatments influence leaf area characteristics. The
research was carried out during two consecutive years (2019-2020) on
'Merlot'/41B combination grapevines cultivated in the Tekirdağ, Şarköy
vineyards of Chateau Kalpak. Four distinct water stress levels (S0, S1,
S2, and S3) were implemented based on measurements of leaf water
potential. Additionally, defoliation treatments were applied, including
Control (C), Full Window (FW), Right Window (RW), and Left Window
(LW). Upon analyzing leaf characteristics, a clear trend emerged,
wherein higher stress levels correlated with an increased area of primary,
lateral, and total leaves per vine. Concerning leaf removal interventions,
the application of FW led to a reduction in all criteria except for the total
area of main leaves per vine. While FW causes a decrease in certain leaf
parameters under controlled conditions, the stress-induced increase in
total leaf area points to the mechanism of plasticity in grapevines and
warrants further investigation under different environmental and
production dynamics.