The conservation of water has become an increasingly important practice, especially in western states and throughout the state of California where competition for quality water is increasing as a result of overall population demands and the need to provide irrigation water for agricultural crops (Parsons, 2000). Many states have also begun using treated, reclaimed municipal wastewater as a source of irrigation water for agricultural crops to reduce the need for high quality water (Carter et al., 2005b; Parsons, 2000). Horticultural crops, especially cut flowers, are ideal for use with saline or wastewater reuse irrigation because they are not used for consumption and they are high-value crops. In 1998, 431 operations in the United States sold 55.2 million spikes of snapdragons totaling $22.4 million. Seventy-seven of these operations were located in California where annual sales approached $13.7 million (Census of Horticultural Specialties, 1998). Prince and Prince, Inc. (2003) reported that nearly three million bunches of snapdragons were produced in California alone.
Cut-flowers, like with most horticultural crops, are glycophytes generally believed to have little or no tolerance to salinity (Grattan and Grieve, 1999; Greenway and Munns, 1980). In most cases, exposure to salt stress results in injury or death resulting from salinity-induced nutritional disorders (Grattan and Grieve, 1999). Yet many floral crops, including statice, cockscomb, stock, and sunflower, have shown varying levels of tolerance to salinity (Carter and Grieve, 2006; Carter et al., 2005a, 2005b; Grieve et al., 2006).
Most floriculture operations in California are located along the coast where growers irrigate their crops with groundwater. Recently, however, many growers have recognized that sea water intrusion is occurring and is contaminating their source of high-quality water. One of their concerns is how crops will respond to increases in salinity caused by infiltration of sodium chloride, the primary salt in sea water, into the groundwater (Carter et al., 2005a). Another consideration is the release of effluents that contain high amounts of nutrients and salts by nursery and greenhouse operators into local streams, aquifers, and rivers. Many growers have responded by recycling discharge effluents for reuse in their own operations or in nearby agricultural systems (Carter et al., 2005a). A third consideration is that producers are finding it more lucrative to sell their coastal property as the value of their real estate increases and relocate further inland to areas such as the Imperial and Coachella Valley (ICV). Some growers are actually expanding operations in the ICV. Agricultural crops in this region are irrigated with water from the Colorado River, which contains salts and nutrients arising from agricultural runoff from upriver agricultural operations throughout the Colorado River watershed. Magnesium and calcium sulfate-based salts are found in this soil and irrigation water in addition to sodium chloride (Carter et al., 2005a). Salinity of the water from the Colorado River watershed varies depending on the sampling location. In the Imperial Valley, salinity has been measured at 1.48 dS·m−1 and in Yuma, AZ, salinity has been recorded at 1.38 dS·m−1 (Ayers and Westcot, 1985). Growers find it important to understand how their crops will respond to different combinations and types of salts.
Typically, plants at earlier stages of development do not always demonstrate the same levels of tolerance as their mature counterparts (Waisel, 1989). The seed and seedling stages of development are particularly vulnerable to increases in salinity because plants in these stages have not yet developed the physiological mechanisms to tolerate increasing salinity concentrations (Adam, 1990). In fact, seeds of halophytes have been reported to show their highest percentage of germination under nonsaline conditions (Carter et al., 2005b; Ungar, 1991). However, Carter et al. (2005b) found that seeds of Limonium perezii demonstrated the highest germination under moderately saline conditions. Understanding the salt tolerance limits at the germination stage of development allows growers to produce their crops from seed using saline wastewaters if the seeds demonstrate high germination percentages under increasing saline conditions.
Antirrhinum majus L. (Scrophulariaceae) (snapdragon) is a perennial native to the Mediterranean region. However, it is treated as an annual when grown in gardens and as a cut flower (Gleason and Cronquist, 1991). Its irregular-shaped flowers occur in terminal racemes and are variously colored. Monk and Peterson (1961) showed that snapdragons (‘Super Majestic’) could survive when irrigated with solutions having salt concentrations up to 60 meq·L of sodium and calcium chloride, but not up to 120 meq·L. Given its ability to tolerate saline irrigation water and its economic importance to the cut flower industry, A. majus was selected as a potential cut flower crop for saline environments. ‘Monaco Rose’ and ‘Apollo Cinnamon’ were selected based on their growing conditions and flowering times and are designated as Group 2 and 3 varieties, respectively (Corr and Laughner, 1998).
The goals of this investigation were to: 1) determine whether marketable cut flowers, as determined by stem length, of two A. majus varieties could be produced when grown in two different increasingly saline irrigation water compositions; 2) assess the mineral nutrition of two varieties of A. majus when exposed to increasingly saline irrigation water; 3) assess changes in morphology for each variety as salinity increased in irrigation waters differing in ion compositions; and 4) determine the germinability of seeds from two varieties of A. majus when exposed to increasingly saline irrigation water.
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