Conditions in the parental environment during reproduction can affect the performance of the progenies. The goals of this study were to investigate whether warm or cold temperatures in the parental environment during flowering and seed development affect Arabidopsis thaliana seed properties, growth performance, reproduction and stress tolerance of the progenies, and to find candidate genes for progeny-related differences in stress responsiveness. Parental plants were raised at 20°C and maintained from bolting to seed maturity at warm (25°C) or cold (15°C) temperatures. Analysis of seed properties revealed significant increases in nitrogen in seeds from warm temperature and significant increases in lipids and in the ratio of a-linolenic to oleic acid in seeds from the cold parental environment. Progenies of the warm parental environment showed faster germination rates, faster root elongation growth, higher leaf biomass and increased seed production at various temperatures compared with those from the cold parental environment. This indicates that under stable environmental conditions, progenies from warm parental environments had a clear adaptive advantage over those from cold parental environments. This parental effect was presumably transmitted by the higher nitrogen content of the seeds developed in warm conditions. When offspring from parents grown at different temperatures were exposed to chilling or freezing stress, photosynthetic yield recovered faster in progenies originating from cold parental environments. Cold acclimation involved up-regulation of transcripts of flavanone 3-hydroxylase (F3H) and pseudo response regulator 9 (PRR9) and down-regulation of growth-associated transcription factors (TFs) NAP and AP2 domain containing RAP2.3. NAP, a regulator of senescence, and PRR9, a temperature-sensitive modulator of the circadian clock, were probably involved in mediating parent-of-origin effects, because they showed progenyrelated expression differences under chilling. Because low temperatures also delay senescence, cold responsiveness of NAP suggests that this factor is linked with the regulatory network that is important for environmental acclimation of plants.

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The influences of seed—nursery environment upon genecological characteristics of 20 medusahead strains was studied. Environmentally induced variation was observed in germination, early height development, and winter survival. Small, but significant, variation in dates of spike emergence and anthesis, caused by differences in seed—nursery environment, were observed. Results suggest that the common practice of attaching genecological significance to wild—grown seed may be subject to error, especially in germination and early phenological stages following germination.

A search continues for native pered range grasses which will COmpde SUCCS~S~UU~ rritb intduet~d SIUIUI ~WW. &CN bluebunch wbeatpur (Abropyron qkatum) Is a recently released cultivar rleeted for seedling vigor. Medusahead (Taeniatherum uspmm) seeds gemninded in about one third tbe time, were less inhibited by cold temperaturea typical of range conditions, and seedling grew more than twice 8s fast as Sec8r in a 30&y trial. Indications are that even tbh new cultivu will not compete succeasfully with vigorous medusabead seedlings without initial weed control.

Highlight Seeds of crested wheatgrass (Agropyron desertorum [Fisch. ex Link] Schult.), planted at a depth of 1 inch, germinated well because of relatively constant and favorable moisture conditions. These seeds rapidly synthesized hexose phosphate, uridine diphosphate hexose, nicotinamide adenine dinucleotide, adenosine diphosphate, adenosine triphosphate, and other phosphate esters. Synthesis began 2 to 4 weeks before germination was observed. In contrast, seeds on the soil surface failed to germinate because of generally unfavorable and rapidly fluctuating moisture conditions. Adenosine triphosphate, the principal phosphate ester formed in these seeds during brief periods of precipitation, was broken down during periods of drought. Although these measurements include only a few of the biochemical reactions that occur in seeds, they contribute to an understanding of the environmental conditions that promote or retard germination processes and help explain the reasons for success or failure of seedjngs on semiarid rangelands.