Photosynthetic abilities, light response, and stomatal function in six agroforestry species, Dipterocarpus tuberculatus, D. alatus, Eucalyptus camaldulensis, Hevea brasiliensis, Colocasia gigantea, and C. esculenta in responses to water deficit Kwankhao Cha-um a , Sirikorn Sangjun a , Kunyapon Prawetchayodom a , Sukanya Klomklaeng a , Suriyan Cha-um b, *

Plants produce a variety of crystals with different shapes and sizes. Based on their appearance, calcium oxalate crystals, especially raphides, have been suggested to play a key role in the defense mechanism against insect attack and microbial infections. Colocasia esculenta, a tropical plant primarily grown for its edible corms contains a large number of cells (idioblasts) with needle-like crystals of calcium oxalate (i.e., raphides). The concentration of raphides in the plant varies with the ploidy level, cultivar, organ, and micro environment. The objective of this study was to evaluate the physiological, organic and inorganic biochemical changes in the differentiated leaves of elephant ear (Colocasia esculenta var. aquatilis) and examine the rate of release of these compounds in water soluble forms. Regarding photosynthetic functions, the net photosynthetic rate (P n) was positively related to light intensity, especially in fully expanded and old leaves. However, the P n , transpiration rate (E), and stomatal conductance (g s) in young leaves were lower than those in fully expanded and older leaves, resulting in low levels of total soluble sugar content in both the petioles and leaf blades of young leaves. In contrast, oxalic acid and calcium in both petioles and leaf blades peaked at > 2.0 mg•g −1 FW and 185 mg•g −1 FW, respectively. A large number of idioblasts (~5.5 idioblasts per observed microscopic field) were observed in young leaves. Oxalic acid and calcium ions extracted from the leaf tissues were rapidly dissolved in hot water (85°C) for 10-15 min, leading to a decline in the number of idioblasts. Based on these results, petioles and leaf organs of elephant ear may be eaten safely after boiling in hot water for 15 min to dissolve CaOx.

The main objective of this study is to find the main factors which affect the migration rate and may lead to brain drain. Brain drain is the migration of highly trained or skilled people to wealthier countries where they can gain more salary and better standard of living. Moreover, brain drain can result in losing professionals and cause deterring effects on the countries. This has become an important issue as in recent years, more people have been leaving their countries to more developed countries. Thus, it is clear that brain drain is a significant issue in various countries including Thailand. Nevertheless, some countries, for instance Taiwan, have developed policies in order to improve their citizens’ life qualities. Finding the main causes of migration may help us understand more about the situation, which may lead to a solution for this issue. There are mainly three levels of brain drain, Geographical brain drain, Organizational brain drain and Industrial brain drain. In this paper, we mainly discuss Geographical brain drain since it has the most substantial impact on the country. Based on 250 respondents who are Thai inhabitants, the result shows that the most significant reason for migration is the standard of living, followed by social conditions.