Programmed cell death (PCD) is the genetically regulated disassembly of cells, and occurs in the endosperm of cereals during seed maturation. Since PCD determines the lifetime of cells, it can affect endosperm growth and, therefore, cereal yield. However, the features and mechanisms of PCD in the developing starchy endosperm in the Poaceae remain unclear. In the present study, we investigated the characteristics of PCD in developing starchy endosperm of rice (Oryza sativa L.) by fluorescence microscopy, focusing on the spatial and temporal progress of PCD-associated responses. Cell death commenced in the central region of starchy endosperm, and then spread to the peripheral region. PCD-associated responses, such as mitochondrial membrane permeabilization and activation of the protease that cleaves the amino acid sequence VEID, showed similar spatial patterns to that of cell death, but preceded cell death. Degradation of nuclear DNA could not be detected in developing starchy endosperm by the TUNEL assay. These results indicated that PCD in developing starchy endosperm of rice proceeds via a highly organized pattern. In addition, these results suggested that PCD in developing starchy endosperm of rice is characterized by the involvement of mitochondrial signaling and the activity of a caspase-like protease that cleaves the VEID sequence.
Some plants are able to tolerate salinity using salt glands on the leaf surface, which secrete excess salts transported into the leaves. Rhodes grass (Chloris gayana Kunth) reportedly possesses such salt glands, but the features of secretion remain unclear. In the present study, we compared the ability of Rhodes grass salt glands to secrete sodium and potassium with the aim of clarifying the preference of cations for secretion. In both whole plant experiments and detached leaf experiments, NaCl treatment increased Na + secretion and KCl treatment increased K + secretion. When the ratios of the amount of secreted ions to their concentration in the leaves were compared between Na + and K + , the ratio was greater with Na + than K + .
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