An Expanded Clay Pebble, Continuous Recirculating Drip System for Viable Long-Term Hydroponic Grapevine Culture

Abstract

Grapevines were grown for more than one month in aerated solution culture (ASC) and developed nutrient deficiency-like symptoms. After eliminating possible problems with pests, pathogens, or nutrient concentrations in the solution, we hypothesized that the roots suffered from hypoxia because of oxygen diffusion limitations. A continuous recirculating drip system (RDS) was designed to provide precise nutrient control, consistent water potentials, and approximate a well-drained soil. Two-year-old Cabernet Sauvignon vines grown for 37 days in the RDS grew vigorously and were healthy. In contrast, vines in ASC grew less vigorously, eventually displaying leaf nutrient deficiency symptoms and root deterioration. Photosynthesis, photosystem II function, and stomatal conductance were reduced after 37 days in ASC compared with the RDS. The steady-state transcript abundance of two hypoxia-induced transcripts, alcohol dehydrogenase II and α-amylase, increased slowly after six days in ASC but not in the RDS. These results indicated that mature vines with woody roots suffered slow and chronic hypoxic stress in ASC. In contrast, vines grown in the RDS did not suffer hypoxic symptoms. Thus, the RDS appeared to approximate a well-drained soil and was ideal for long-term greenhouse growth of grapevines, maintaining the advantages that solution culture provides for controlled abiotic-stress experimentation and ease of root harvest.