Semi-viviparous embryo development and dehydrin expression in the mangrove Rhizophora mucronata Lam.

Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55–65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6–8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression

XVI.—The new flora of Krakatao

Volume: 3Start Page: 141End Page: 14

Susceptibility of several sahelian Acacia to Meloidogyne

Four Acacia species were tested for their susceptibility to the root-knot nematode, Meloidogyne javanica, commonly found in sahelian areas. Faidherbia albida and Acacia senegal were resistant to this nematode. On the contrary, A. raddiana, A. nilotica and A. mangium were susceptible. Among these three species, the growth of A. nilotica and A. mangium was inhibited by M. javanica but A. raddiana was tolerant. The rhizobial symbiosis with F. albida and A. senegal was stimulated by the nematode. The population build-up of the root-knot nematode induced by tree species in agroforestry systems is discussed

The benefits of bathing buds: water calyces protect flowers from a microlepidopteran herbivore

Protective floral structures may evolve in response to the negative effects of floral herbivores. For example, water calyces—liquid-filled, cup-like structures resulting from the fusion of sepals—may reduce floral herbivory by submerging buds during their development. Our observations of a water-calyx plant, Chrysothemis friedrichsthaliana (Gesneriaceae), revealed that buds were frequently attacked by ovipositing moths (Alucitidae), whose larvae consumed anthers and stigmas before corollas opened. Almost 25% of per-plant flower production was destroyed by alucitid larvae over two seasons, far exceeding the losses to all other floral herbivores combined. Experimental manipulation of water levels in calyces showed that a liquid barrier over buds halved per-flower alucitid egg deposition and subsequent herbivory, relative to buds in calyces without water. Thus, C. friedrichsthaliana's water calyx helps protect buds from a highly detrimental floral herbivore. Our findings support claims that sepal morphology is largely influenced by selection to reduce floral herbivory, and that these pressures can result in novel morphological adaptations