Effects of Substrate Water Content on Morphology and Physiology of Rosemary, Canadian Columbine, and Cheddar Pink

Abstract

<jats:p>Two experiments were conducted to determine how different substrate volumetric water contents (θ equals volume of water per volume of substrate) affected morphology and physiology of three popular perennials using a capacitance sensor-automated irrigation system. In the first study, rosemary (<jats:italic>Rosmarinus officinalis</jats:italic>) was grown at one of eight θ set points ranging from 0.05 to 0.40 L·L<jats:sup>−1</jats:sup>. In the second study, Canadian columbine (<jats:italic>Aquilegia canadensis</jats:italic> ‘Pink Lanterns’) and cheddar pink (<jats:italic>Dianthus gratianopolitanus</jats:italic> ‘Bath’s Pink’) were grown at one of nine θ set points ranging from 0.05 to 0.45 L·L<jats:sup>−1</jats:sup>. Total leaf number and area as well as shoot fresh and dry weight of rosemary plants grown at θ of 0.20 L·L<jats:sup>−1</jats:sup> or greater were approximately twice that of those grown at lower θ. Canadian columbine height increased as θ increased. Leaf area of cheddar pink grown at θ of 0.35 L·L<jats:sup>−1</jats:sup> or higher was twice that of plants grown at the lowest θ. Shoot dry weight of Canadian columbine was not significantly affected by θ. Shoot dry weight of cheddar pink responded quadratically to increasing θ and peaked at θ of 0.35 L·L<jats:sup>−1</jats:sup>. θ also significantly influenced photosynthetic activities; net photosynthetic rate (A<jats:sub>N</jats:sub>) and stomatal conductance (<jats:italic>g</jats:italic><jats:sub>s</jats:sub>) of Canadian columbine increased with increasing θ. A<jats:sub>N</jats:sub> of cheddar pink also increased as θ increased. Greater water volumes were applied to maintain higher θ set points. Irrigation water use efficiency (IWUE = shoot dry weight ÷ total amount of water applied per plant) of Canadian columbine and cheddar pink was not influenced by θ. Growth of all three plants was reduced when grown at lower θ; in the case of cheddar pink and Canadian columbine, this was attributable at least in part to reduced A<jats:sub>N</jats:sub>.</jats:p>

Substrate Volumetric Water Content Controls Growth and Development of Containerized Culinary Herbs

“…The growth and development of containerized basil, dill, parsley, and sage is promoted with increasing substrate VWC. While the effect of substrate moisture on growth is better understood for containerized ornamental flowering crops, our results on the effect of substrate VWC on controlling growth of culinary herbs align well with the limited literature on container-grown herbs, including rosemary and English lavender [8,9]. For example, Zhen et al [8] reported that, as substrate VWC increased from 0.05 to 0.40 m 3 ·m −3 , the height, width, leaf number and area, and fresh and dry mass of rosemary increased linearly.…”

“…Additionally, restricting P to 5 mg·L −1 produced basil, dill, parsley, and sage shorter than plants provided with 40 mg·L −1 [5]. While cultivar selection and nutrient management are useful forms of nonchemical growth control, it may be necessary to use multiple nonchemical methods of controlling growth to achieve the degree of control required in the absence of PGRs.Reducing irrigation or substrate volumetric water content (VWC), commonly referred to as "deficit irrigation", is another effective method of controlling containerized plant growth [6][7][8]. The water available for plant uptake increases and growth is promoted as substrate VWC increases and, as such, restricting irrigation and reducing the substrate VWC can diminish turgor pressure and subsequent stem extension and growth [9].…”

“…While controlling the substrate VWC clearly has potential for use in containerized herb production, data specific to the effects of substrate VWC on containerized herb growth are lacking.We have found some limited reports on the effects of substrate moisture on containerized perennial herb growth [8,9]. Zhen et al [8] reported that limiting irrigation of rosemary (Rosmarinus officinalis L.) plants successfully controlled excessive growth. Additionally, Zhen and Burnett [9] showed that English lavender (Lavandula angustifolia Mill.…”

“…Reducing irrigation or substrate volumetric water content (VWC), commonly referred to as "deficit irrigation", is another effective method of controlling containerized plant growth [6][7][8]. The water available for plant uptake increases and growth is promoted as substrate VWC increases and, as such, restricting irrigation and reducing the substrate VWC can diminish turgor pressure and subsequent stem extension and growth [9].…”

“…We have found some limited reports on the effects of substrate moisture on containerized perennial herb growth [8,9]. Zhen et al [8] reported that limiting irrigation of rosemary (Rosmarinus officinalis L.) plants successfully controlled excessive growth. Additionally, Zhen and Burnett [9] showed that English lavender (Lavandula angustifolia Mill.…”