Seed maturation and germination

Using the scutella of maize, our laboratory has been studying the synthesis and degradation of the lipid bodies during seed maturation and germination. In order to delineate the mechanism of deposition and utilization of triacylglycerols in the lipid bodies, we study the last... 

Fig. 4. Schematic Illustration of the synthesis and degradation of a lipid body In the maize scutellum during seed maturation and germination. See text for explanation. RER, rough endoplasmic reticulum FA, fatty acid tri, trlacylglycerol, PL, phospholipid free, free polyribosomes.

M. Sponsel, The localization, metabolism and biological activity of gibberelllns in maturing and germinating seeds of Pisum sativtim cv. Progress No. 9, Planta 159 454 (1983). 

It Is assumed that most of the proteins of the lipid body membrane are synthesized during seed maturation and not germination. Some proteins, of Important but of minor quantities (e.g., lipase, to be described) or of unknown functions (15) are apparently synthesized during germination. 

XXXVII. Characterization of the 8-oxidation system from maturing and germinating castor bean seeds. Plant Physiol. 44 508 (1969). 

The germination stimulant or stimulants from host plants have not yet been identified, but research on isolation and identification of these allelopathic compounds continues. Other nonhost plants, such as cotton, also release chemicals which stimulate the germination of witchweed seed and these crops can replace the cereal crops in witchweed-infected fields. If no acceptable host is present, the witchweed plant is unable to mature and produce seed. The importance of cereal crops as a staple food in underdeveloped countries makes growth of nonhost crops only partially acceptable, and there are numerous wild hosts that allow the witchweed to germinate, mature, and produce more seed (several thousand seeds can be produced by a single plant). Nevertheless, application of either natural or synthetic stimulants in the absence of a host plant is an effective way of reducing and eventually eliminating the witchweed problem. 

ABA produce more mature seeds showing primary dormancy than the wild-type plants. A reduced dormancy often occurs in seeds of ABA-insensitive mutants. Gibberellin A (GA) is absolutely required for germination of the wild-type Arabidopsis seeds. Seeds of ethylene-insensitive and GA-insensitive mutants are supersensitive to exogenous ABA, which suggests that in imbibed seeds ethylene and GA may directly counteract the action of ABA in dormancy maintenance. ... 

Zimmerman, D.C., Sunflower seed germination as influenced by maturity and etherel treatment, Proc. Sunflower Forum, 2, 25-26, 1977. 

The purine is s)mthesized and stored in large quantities in the seed. Directly after germination, caffeine remains in the cotyledons surrounding the endosperm and does not migrate to the h)7pocotyl or root. In older seedlings, caffeine accumulation continues during leaf expansion, and in the mature plant the fruits actively synthesize purine alkaloids as they mature (Aerts and Baumann, 1994). 

Cuphea oils are interesting because they come from annual plants producing glycerol esters based mainly on capric (10 0) or lauric acid (12 0) or occasionally on caprylic (8 0) or myristic acid (14 0). Cuphea plants exhibit several wild plant characteristics that need to be bred out. These include dormancy, nonuniform germination, indeterminate flowering, seed maturation over a broad time period (six weeks), extreme dehiscence (pod shattering), and the presence of viscid hairs on stem, leaves, flowers, and fruit. Several species are being studied in attempts to make them commercial (30). 

It may be predicted that, in the absence of physical stress of wind and snow blast, as in most tropical mountains below the snow line, the treeline should be highly dynamic within a long term temporal scale because trees are slow to establish, grow and mature. Thus, it is likely that other limitations to tree seed setting and growth are at play. One of these constraints is in fact seed germination in sites exposed to UV-B radiation (see section 5.3)... 

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