To distinguish their roles in early kernel development and stress, expression of soluble (Ivr2) and insoluble (Incw2) acid invertases was analyzed in young ovaries of maize (Zea mays) from 6 d before (−6 d) to 7 d after pollination (+7 d) and in response to perturbation by drought stress treatments. The Ivr2 soluble invertase mRNA was more abundant than the Incw2 mRNA throughout pre- and early post-pollination development (peaking at +3 d). In contrast,Incw2 mRNAs increased only after pollination. Drought repression of the Ivr2 soluble invertase also preceded changes in Incw2, with soluble activity responding before pollination (−4 d). Distinct profiles of Ivr2and Incw2 mRNAs correlated with respective enzyme activities and indicated separate roles for these invertases during ovary development and stress. In addition, the drought-induced decrease and developmental changes of ovary hexose to sucrose ratio correlated with activity of soluble but not insoluble invertase. Ovary abscisic acid levels were increased by severe drought only at −6 d and did not appear to directly affect Ivr2 expression. In situ analysis showed localized activity and Ivr2 mRNA for soluble invertase at sites of phloem-unloading and expanding maternal tissues (greatest in terminal vascular zones and nearby cells of pericarp, pedicel, and basal nucellus). This early pattern of maternal invertase localization is clearly distinct from the well-characterized association of insoluble invertase with the basal endosperm later in development. This localization, the shifts in endogenous hexose to sucrose environment, and the distinct timing of soluble and insoluble invertase expression during development and stress collectively indicate a key role and critical sensitivity of the Ivr2soluble invertase gene during the early, abortion-susceptible phase of development.

Asian Mega deltas (AMDs) are among the world´s most important rice‐growing areas and vital for food security. This review describes the major environmental and agricultural characteristics as well as current and future threats to food production and livelihood, using three AMDs as examples, namely the Ganges–Brahmaputra delta in Bangladesh, the Ayeyarwady delta in Myanmar and the Mekong River delta in Vietnam. In addition, we analysed the most widely used agricultural adaptation methods in these areas. The major threat to agriculture is salinity intrusion and water scarcity, which consequently leads to a shortage of irrigation water and yield reduction. The most common applied agricultural adaptation strategies are the use of salt‐tolerant varieties and the adjustment of cropping calendars, as well as the use of water‐saving technologies. It was found that there are many concepts that address individual problems, but a comprehensive and integrated concept for delta regions to adapt to climate change is still missing.