Salinity is one of very serious problem for agricultural sector in the world. Soil salination is the accumulation of free salts to such an extent that it leads to degradation of soils and vegetation. Salinity stress has become a dominant environmental constraint that limits crop productivity in most arid and semi-arid regions of the world.

Salinity is currently one of the most severe a biotic factors limiting agricultural production. Salinity of soil and water is caused by the presence of excessive amounts of salts. In arid and semiarid lands, the plants are subjected through their life cycle to different stresses; some of these plants can tolerate these stresses in different ways depending on plant species and the type of stress.

Salinity in farm land was caused by sea water intrusion that makes the farm land become saline. Sea water intrusion hindered the agricultural production along coastline. Nevertheless, rise in sea level because of global warming makes wider range of land affected by tidal fluctuation that caused salinity included in farm land. The new model predictions indicate that the ocean will rise between 0,9 and 1,3 meters.

Shallots called ‘bawang merah’ is very important spices in Indonesia, it is included in vegetable that as learn very sensitive to salinity. Shallots are severally planted near coastline such as in Brebes Central Java and Bantul special province of Yogyakarta. Over the time, the sea water intrusion is getting often and greater to the farm land that expanded along the coastline, and because of sea water intrusion there are a lot of farm land were unproductive anymore. We need to overcome this problem, not only from agronomy technology perspective, yet we have found the appropriate varieties that could survive in saline condition to guarantee food chain supply.

To scan how the influence of salinity on plants especially in shallot, it is necessary to do some observations on plant organs. Shoot is the most easily observed and reacted quite responsive on increasing salt concentration in the environment.

Salt stress has three fold effects which reduces water potential and causes ion imbalance on disturbances in ion homeostasis and toxicity. High salinity (high EC) causes reduced plant growth, plant cell dehydration, and possibly death in less tolerant plants. Salinity is an environmental stress that limits growth and development in plants. The response of plants to excess NaCl is complex and involves changes in their morphology, physiology, and metabolism. Salinity has a dual effect on plant growth via an osmotic effect on plant water uptake, and specific ion toxicities. By decreasing the osmotic potential of the soil solution, plant access to soil water is decreased, because of the decrease in total soil water potential. Soil salinity affects plant growth and development by way of osmotic stress, injurious effects of toxic Na⁺ and Cl^– ions and to some extent Cl^– and SO4 ^{2 –} of Mg²⁺ and nutrient imbalance caused by excess of Na+ and Cl– ions.

This altered water status leads to initial growth reduction and limitation of plant productivity The salinity of irrigation water as a cause of yield reduction has been the subject of many investigations. The salinity effect seems to depend also on other factors such as soil properties, climate, cultural practices and water management. Whereas many data are available with regard to the effect of salinity on crop yield, a great deal less is known about the physiological processes during growth. Studies concerning the effect on crop yield are generally not combined with studies on crop physiology, the first group being conducted in the field and the second mainly in the laboratory. At increasing salinity water potential of the leaf and the stomatal conductance decreased, the difference in radiation temperature increased, and the leaf area, dry matter production and yield were reduced.

Salt stress could decreased water potential, in which make plant difficult to absorb water. The first variable observed is stomata behavior. Stomata is a pathway for transpiration, therefore the increasing of stomata closure in saline condition would pursue the transpiration rate. Leaves have the lowest water potential compared to the other organ. Leaf condition could use to figure out plant response to environment stress related to water condition.

Plant in a water and salt stress will suffer of decreasing turgor pressure because unbalanced water uptake which has caused decreasing of stomata opened in the mechanism of controlling plant water status. Stomata opened described stomata activity which was influenced by turgid pressure. In this research, even though stomata density showed immeasurable condition, but majority of shallot stomata opened were decreasing in saline compared to normal condition.

On a research using several variety of Indonesian diploid shallot which are Tiron, crok, biru, bauji, sumenep, palu, Thailand, Super Philip, WxB (crossing between white Dilli and Bantul Shallot), Triploid shallot coded AAA No.8 and Tetraploid shallot coded Dili Red c 1-2-6,that treated with Saline condition on EC 8 dS/m, showed that the shallot leaves quality decreased significantly. Salinity decreased the length and wide of leaves epidermal cell and decreasing stomata opened. This condition affected the plant ability in photosynthesis process that in the end will reduce the shallot yield.

Reference

Ali, Y., Z Askam., M.Y. Ashraf dan G.R. Tahir. 2004. Effect of salinity on chlorophyll concentration, leaf area, yield and yield components of rice genotypes grown under salin environment. International Journal of Environmental Science & Technology 1(3) : 221-225

Putri,F. 2008. Effect of Salinity on Several Varieties and Different Ploidy Level of Shallot. Thesis. Universitas Gadjah Mada.Yogyakarta

Sairam, R. K. and A. Tyagi. 2004. Physiology and molecular biology of salinity stress tolerance in plants. Current Science 86 (3): 407-421.

Warner, D.A., M.S.B, Ku and G.E, Edwards. 1987. Photosynthesis, leaf anatomy, and cellular constituents in the polyploid C4 grass panicum virgatum. Plant Physiology (84): 461 – 466