Pattern and Significance of Seedling Development in Titanotrichum oldhamii (Gesneriaceae)

The seedling development of Titanotrichum oldhamii (Hemsl.) Solereder has been investigated to provide insight into the evolution and systematic position of Titanotrichum. In T. oldhamii, the size differentiation of the two cotyledons begins while the hypocotyl grows. However, both of the two cotyledons develop normally and locate at the same level. Finally, the two cotyledons are almost equal in size. The aerial shoot (including stem and leaves) is produced from the permanent activity of the apical meristem in the plumular bud. Even though the seedling development in Titanotrichum basically conforms to the general growth pattern of the seedling in the Cyrtandroideae, it is remarkably different from that of other Cyrtandroideae. Based on the revealed evidence in seedling development in Titanotrichum and other comparative data, the authors have evaluated the possible evolutionary pathway of Titanotrichum and further discussed the familial placement of this genus.

Effects of Extracts from Albizia （Fabaceae） Endemic Species of Madagascar on Vegetable Seedling Development

The effects of extracts from five Albizia （Fabaceae） endemic species from Madagascar （A. arenicola, A. boivini, A. bernieri, A. polyphylla and A. tulearensis） were tested on vegetable seedling development. Crude extracts were obtained through cold or hot extraction methods on dried powdered seeds, seed teguments, leaves or empty pods. They were thereafter purified using techniques based on physicochemical properties of active substances. Assays were carried out on seedling growth of Monocotyledons and Dicotyledons representatives. Results showed that all extracts exerted significant dose dependent inhibition on epicotyl and hypocotyl growth. However, some extracts exhibited a slight stimulation effect at low doses. Moreover, A. arenicola crude extract （E23） slightly inhibited axillary bud growth, while A. tulearensis crude extract （ET1） showed a stimulation effect. According to preliminary phytochemical screening results, these effects might be due to saponins or alkaloids.

Arabidopsis small ubiquitin-related modifier protease ASP1 positively regulates abscisic acid signaling during early seedling development~~

The small ubiquitin-related modifier （SUMO） modification plays an important role in the regulation of abscisic acid （ABA） signaling, but the function of the SUMO protease, in ABA signaling, remains largely unknown. Here, we show that the SUMO protease, ASPI positively regulates ABA signaling. Mutations in ASPI resulted in an ABA-insensitive phenotype, during early seedling develop- ment. Wild-type ASP1 successfully rescued, whereas an ASPI mutant （C577S）, defective in SUMO protease activity, failed to rescue, the ABA-insensitive phenotype of asp1-1. Expression of ABI5 and MYB3o target genes was attenuated in asp^-I and our genetic analyses revealed that ASP1 may function upstream of ABI5 and MYB3o.

Characters of Cysteine Endopeptidases in Wheat Endosperm during Seed Germination and Subsequent Seedling Growth

The endopeptidases （EPs） in wheat endosperm during seed germination and subsequent seedling growth were characterized by gradient-polyacrylamide gel electrophoresis with gelatin copolymerized into the gel. Four cysteine EPs （EP1, EP2, EP3 and EP4） were detected in wheat endosperm during the 7 d growth after seed imbibition. The results also showed that the activities of all of these EPs increased continuously, and EP2 first appeared and had the highest proteolytic activity among the four EPs in this experimental process. The optimum pH and temperature of all four EPs were 4.0 and 40.0 ~C. All EPs were completely inhibited by 25 μmol/L E-64 and had no good thermal stabilities, especially EP1. In addition, these EPs had different substrate specificities to albumins, globulins, gliadins and glutenins; the main storage proteins of mature wheat endosperm. Among them, EP2 had the highest proteolytic activities on globulins, gliadins and glutenins, and might be the most important and specific EP with potential to be tightly correlated with seedling development.

Radicle pruning by seed-eating animals helps oak seedlings absorb more soil nutrient

Although radicle pruning has well been observed in plant-animal interactions,research has not been conducted to determine how radicle pruning by seed-eating animals regulates nutrition mobilization of cotyledonary reserves and absorption of soil nutrients.We used stable nitrogen isotopes to test how acorns of early-germinating oak species(Quercus variabilis,Q.aliena,and Q.mogolica)trade off nutrients in the cotyledons and those in the soil in response to radicle pruning by seed-eating rodents.Radicle pruning by rodents resulted in root branching in the 3 early-germinating oak species.Moreover,radicle pruning increased shoot dry weight and substantially reduced the root-to-shoot ratio of oak species.Corresponding to the decreased dry weight of roots and root-to-shoot ratio,the dry weight of the remnant cotyledons was higher after radicle pruning in the 3 oak species.We provided first evidence that radicle pruning by seed-eating animals improved seedling performance of early-germinating oaks by increasing absorption of nutrients from soil.The results indicate that early-germinating oak seedlings trade off nutrition budget by altering nutrient absorption from soil and reserve mobilization from cotyledons in response to radicle pruning by seed-eating animals.Our study provided new insight into the nutrition allocation mechanism of young seedlings in response to radicle pruning by seed-eating animals,reflecting a mutualistic interaction between early-germinating oak and food-hoarding animals.