Multinucleate storage cells in Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) and the effect of seed parasitism by the chalcid Megastigmus spermotrophus Wachtl

Abstract

Megagametophytes of Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) accumulated storage products following fertilization. As megagametophytes matured, the number of nuclei per cell rose, resulting in syncytial storage cells. Studies carried out on trees in France and Canada confirmed that such previously unreported, free nuclear cells were a normal part of late megagametophyte development. Unfertilized megagametophytes showed that some binucleate cells before degeneration resulted in empty seed. Insect parasitism prevented megagametophyte abortion in unfertilized ovules. Oviposition by a torymid chalcid wasp (Megastigmus spermotrophus Wachtl) early in megagametophyte development resulted in normal megagametophyte development. Around the time of plant egg maturation, binucleate and trinucleate cells were observed. As megagametophytes matured, multinucleate mature storage cells rich in proteins, lipids and starch were formed. The insect was able to induce identical nuclear behaviour in infested, unfertilized megagametophytes, as that of uninfested, fertilized megagametophytes. Heredity (2005) 94, 616-622.

Thermal and hyperspectral imaging for Norway spruce (Picea abies) seeds screening

“…does not interfere with normal megagametophyte development. As a consequence, storage products are still stored in spite of its continuous reduction due to insect feeding (Von Aderkas et al, 2005). It is therefore expected to have spectral differences between the three seed classes in the absorption peaks of those compounds.…”

Pine embryogenesis

“…20 The degeneration of the Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] megagametophyte is prevented if the seed is parasitized by the chalcid larva (Megastigmus spermotrophus Wachtl.). Moreover, the larva is able to evoke the production of storage reserves, 21 which has also been observed in Norway spruce seeds infected by the spruce seed gall midge (Plemeliella abietina Seitn.) (Tillman-Sutela E…”

Endogenous cytokinins, auxins and abscisic acid inUlva fasciata(Chlorophyta) andDictyota humifusa(Phaeophyta): towards understanding their biosynthesis and homoeostasis

“…However, in vascular plants, ABA levels are strongly dependent on the duration of the water stress, for example in Arabidopsis thaliana (Go´mez-Cadenas et al, 2002;Lo´pez-Carbonell & Ja´uregui, 2005) and tobacco (Hradecka´et al, 2007). ABA catabolism has been examined in Brassica napus siliques (Zhou et al, 2003), lettuce seeds (Chiwocha et al, 2003), Western white pine seeds (Feurtado et al, 2004(Feurtado et al, , 2007 and in Douglas fir seeds (von Aderkas et al, 2005). Well-watered plants contained relatively constant, low levels of endogenous ABA (5-50 pmol g À1 FW); while water-stressed plants had 10-50-fold higher ABA amounts with concentrations peaking 24 hours after water stress.…”