Greenhouse Mist Improves Yield of Tomato Plants Grown under Saline Conditions

TLDR: In this paper, the authors investigated the effect of greenhouse misting on tomato plant growth and yield in the Mediterranean spring-summer growing season and found that misting significantly improves tomato crop productivity under nonsaline and saline growth conditions.

Abstract: ADDITIONAL INDEX WORDS. Lycopersicon esculentum, salt stress, plant water uptake, water relations, gas exchange, yield ABSTRACT. High salinity levels in irrigation water available in Mediterranean coastal areas induce a significant loss of yield in greenhouse tomato crops. This loss increases during the spring-summer growing season when high irradiance, temperature, and low humidity occur within greenhouses. This study determined whether salt-induced yield losses could be alleviated by increasing humidity by misting the greenhouse atmosphere. Plants of 'Daniela' tomato (Lycopersicon esculentum Mill.), were irrigated with 0 or 50 mM NaCl added to the nutrient solution and grown under natural greenhouse conditions or under applications of fine mist every 8 min during the day. During midday hours, misting reduced greenhouse air vapor pressure deficit 1.0 to 1.5 kPa and reduced greenhouse air temperature 5 to 7 oC. Mist reduced root water uptake from the medium by 40% in nonsalinized plants and by 15% in saline conditions. Foliar concentration of Na was lower in misted-salinized plants than in nonmisted salinized plants. Less negative leaf water potential and higher leaf turgor were recorded with mist at midday, in both salinized and nonsalinized plants. Midday stomatal conductances and net CO2 assimilation rates of salinized-misted plants were 3 and 4 times higher, respectively, than those recorded in salinized-nonmisted plants. Misted plants increased instantaneous water use efficiency 84% to 100%, as estimated from the ratio of net CO2 assimilation to transpiration. Nonsalinized plants grown with mist increased total leaf area by 38%, dry matter by 10%, and yield by 18% over nonmisted plants. Salinized plants grown with mist increased total plant leaf area by 50%, dry matter by 80%, and yield by 100%. Greenhouse misting resulted in a saving of total water input of 31 L/plant under nonsaline conditions and in greater yields and fruit size regardless of salinity. Results suggest that greenhouse misting, during the Mediterranean spring-summer growing season, improves tomato crop productivity both under nonsaline and saline growth conditions. in the atmosphere and the water vapor differences between roots and leaves (Grange and Hand, 1987). Although toxic effects of salinity on tomato plant growth and yield are widely described, salinity-induced alteration of tomato plant water relations are much less frequently studied (Romero- Aranda et al., 2000). In particular, there is no information avail- able about tomato plant performance under the combined effect of soil salinity and VPD in the greenhouse. The following research was designed to determine the climatic conditions within the greenhouse during the spring-summer growing season and to examine to what degree a simple misting device might increase humidity and low VPD in the greenhouse. We hypothesized that increased greenhouse humidity would improve water relations parameters, growth, and yield of tomato plants grown under moderate saline conditions.