Why there are no plants that produce salt fruits?
Is it because other animals do not like salt to the same degree of humans?
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Soil salinity and sodicity cause severe problems in agriculture worldwide, and salt tolerance in crops is an extremely important trait and a major focus of research. Detrimental effects of high salinity on crops are multifaceted and affect plants in several ways: drought stress, ion toxicity, nutritional disorders, oxidative stress, alteration of metabolic processes, membrane disorganization and reduction of cell division and expansion (Hasegawa et al. 2000; Munns 2002; Muscolo et al. 2007, 2013; Zhu 2007; Sidari et al. 2008). As a result, plant growth, development and survival are reduced (Muscolo et al. 2011; Schleiff and Muscolo 2011). Two major stresses affecting plants under salinity are osmotic and ionic stresses. Osmotic stress, occurring immediately in the root medium on exposure to salts, can result in inhibition of water uptake, cell expansion and lateral bud development (Munns and Tester 2008). Ionic stress develops when toxic ions (e.g. Na+) accumulate in cells causing increase in leaf mortality, chlorosis, necrosis and decrease in the activity of cellular metabolism including photosynthesis (Yeo and Flowers 1986; Glenn and Brown 1999). In fact, excess Na+ and Cl− have the potential to affect plant enzymes, resulting in reduced energy production and other physiological processes (Larcher 1980; Morais et al. 2012a,b). Ionic stress results in premature senescence of older leaves and in toxicity symptoms (chlorosis, necrosis) in mature leaves due to high Na+ and Cl− which affect plants by disrupting protein synthesis and by interfering with enzyme activity (Munns and Termaat 1986; Hasegawa et al. 2000; Munns 2002).
Salt is really good at inhibiting enzymes and biochemistry, which translates into not being great for seeds. So to have a fruit that has a high concentration of salt is really risky and not likely to be successful. Sugars on the other hand attract a multitude of other organism that would help move seeds around or create an ideal growth environment. To have crops that are resilient to salt would be useful but would require a lot of wasted energy to maintain osmoregulation. So it's not so much that animals wouldn't eat a salty fruit but more that it would be harmful to the seeds.