The effect of container volume and pore diameter on the growth of grapevines (Vitis vinifera L.)

Abstract

Two experiments were conducted to investigate the effect of container volume and pore diameter (mean equivalent pore neck diameter - MEPND) on the root and shoot growth of grapevines (Vitis vinifera L.). Rooted cuttings of the cultivar Pinot Noir 'Mariafeld' were grown in containers filled with rounded gravel media in a heated and ventilated glasshouse. Water and nutrients were supplied to each vine by a continuously circulating hydroponic solution.

In Experiment 1, a completely randomised 3 x 3 factorial design with ten replicates was used. Container volume treatments of 150, 640 and 4600 ml, and sieved media particle treatments that gave mean equivalent pore neck diameters of 435, 1780 and 2945 µm, were imposed on vines for 133 days. A blocked 3 x 4 factorial design with ten replicates was used for Experiment 2. Container volume treatments of 60, 120 and 180 ml and mean equivalent pore neck diameter treatments of 365, 630, 1130 and 1885 I'm were imposed on vines for 105 days. Treatment containers were lined with a latex rubber liner impression of the corresponding pore diameter treatments to minimise media - container wall interface effects. Three unlined container volume - pore diameter treatment combinations of ten replicates each were included in addition to the main experiment to test the effectiveness of the container liners.

Decreasing container volume increased the percent of pore volume occupied by roots and reduced root volume, root length, number of roots, shoot length, and shoot dry weight in both experiments. Leaf area, root number: leaf number ratio and root length: leaf area ratio were decreased by smaller container volumes in Experiment 2. Smaller diameter pores increased pore occupation by roots, root volume, root length, number of roots, shoot length, and shoot dry weight in Experiment 1 but decreased them in Experiment 2. Container volume and pore diameter had significant interaction effects on all measured vine parameters except root index in Experiment 1. For Experiment 2, the interactions for root dry weight, root length, root number: leaf number ratio, root length: leaf area ratio, root: shoot ratio and root dry weight: accumulated plant dry weight ratio were significant.

Significant reductions in root growth occurred in Experiment 2 when the total pore volume occupied by roots was between 25 % - 45% in the smallest pore diameter treatment, and between 50% - 65% in the largest pore diameter treatment. Pore diameters of less than 200 µm MEPND were estimated to completely halt root growth.

Root morphology was affected by both container volume and pore diameter. Root index increased with smaller containers in both experiments and with smaller diameter pores in Experiment 2. Reducing pore diameter increased root density and root specific dry weight. Roots were visibly more contorted, shorter and more numerous. Reducing pore diameter in Experiment 1 did not affect roots in the same manner, suggesting that the media was not rigidly confined by the container.

Root: shoot ratio was increased in Experiment 1 and reduced in Experiment 2 by smaller containers. Reducing pore diameter reduced root: shoot ratio in both experiments. The stress imposed on the root system by reducing container volume and pore diameter resulted in the redistribution of dry matter away from the root in favour of the cutting. The effect was greatest in the in the 60 ml 365 µm MEPND treatment, suggesting that the root was severely restricted by the treatments.