Plants synthesize and store oil, mostly triacylglycerol (TAG), in various storage tissues that serves as a source of carbon and energy. The process is transcriptionally controlled by WRINKLED1 (WRI1), a member of the APETALA2 (AP2) class of transcription factors, that regulates most of the fatty acid biosynthesis genes. Among the four Arabidopsis WRI1 paralogs, only WRI2 is nonfunctional and failed to complement wri1-1 mutant seeds. The oleaginous Avocado (Persea americana) fruit mesocarp (60-70% DW oil) showed high expression levels for orthologs of WRI2, along with WRI1 and WRI3. While the role of WRI1 as a master seed oil biosynthesis regulator is well-established, the function of WRI1 paralogs in non-seed tissues is poorly understood. We conducted structural analyses to elucidate distinct features of avocado WRI paralogs compared to their orthologs in seed tissues. Comprehensive comparative in silico analyses of WRI1 paralogs from Arabidopsis (dicot), maize (monocot), and avocado revealed distinct features associated with their function. Our analysis showed the presence of only one AP2 domain in all WRI2 orthologs, compared to two AP2 in others. The highly conserved N-terminal region and the less conserved C-terminal regions make up the primary structure of the proteins, with amino acid composition bias characteristic of intrinsically disordered proteins (IDPs). Additionally, the avocado WRI2 showed a high proportion of random coil secondary structure, although it lacks a C-terminal intrinsically disordered region (IDR). Also, both WRI1 and WRI2 have distinct predicted phosphorylation target sites compared to their orthologs, whereas WRI2 lacks a PEST motif. Finally, through transient expression assays, we demonstrated that both avocado WRI1 and WRI2 are functional and drive TAG accumulation in Nicotiana benthamiana leaves. Our study showed that avocado WRI2 is structurally different and is functional, unlike its ortholog in Arabidopsis. This study provides us with new targets to enhance oil biosynthesis in plants.

A new species of Cucubalus is described based on two fossil seeds recovered from the upper Pliocene Sanying Formation in northwestern Yunnan Province, southwestern China. The seeds are characterized by a reniform to circular outline in shape, and sinuous and discontinuous rugulae made of rod-like elements radiating from the hilum region to the dorsal margin. The combination of these characteristics shows their close resemblance to the extant genus Cucubalus in the Caryophyllaceae. A morphological principal coordinates (PCO) analysis further supports the assignment to this genus. Cucubalus is a monotypic genus today, but the late Pliocene fossil seeds have been described as a new species, Cucubalus prebaccifer Huang, Liu et Zhou, sp. nov. This newly documented Cucubalus fossil, representing the first fossil record of this genus, implies that the genus has existed in northwestern Yunnan, southwestern China, at least since the late Pliocene. It provides important information on the past biodiversity and biogeography of both the genus Cucubalus and the fossil-scant family Caryophyllaceae.

A new species of Cucubalus is described based on two fossil seeds recovered from the upper Pliocene Sanying Formation in northwestern Yunnan Province, southwestern China. The seeds are characterized by a reniform to circular outline in shape, and sinuous and discontinuous rugulae made of rod-like elements radiating from the hilum region to the dorsal margin. The combination of these characteristics shows their close resemblance to the extant genus Cucubalus in the Caryophyllaceae. A morphological principal coordinates (PCO) analysis further supports the assignment to this genus. Cucubalus is a monotypic genus today, but the late Pliocene fossil seeds have been described as a new species, Cucubalus prebaccifer Huang, Liu et Zhou, sp. nov. This newly documented Cucubalus fossil, representing the first fossil record of this genus, implies that the genus has existed in northwestern Yunnan, southwestern China, at least since the late Pliocene. It provides important information on the past biodiversity and biogeography of both the genus Cucubalus and the fossil-scant family Caryophyllaceae.

The occurrences of Staphylea L. (Staphyleaceae) fossils have been abundantly documented from the Cenozoic of Eurasia, but none has been confirmed from North America to date. In this study, we describe Staphylealevisemia sp. nov. on the basis of seed remains from the latest Miocene to earliest Pliocene of northeastern Tennessee, southeastern USA. The seeds are characterized by a smoothly inflated body, a large hilar scar perforated by several vascular traces and bordered by a distinctive lip-like rim, a cuticle coating the seed coat interior, and seed coat section containing weakly developed tiny lumina. According to the paleogeographic distribution of the genus, it is hypothesized that Staphylea originated from western Eurasia no later than the late Oligocene, and arrived in eastern North America no later than the late Neogene, most possibly through the North Atlantic land bridges like many other seed plants.

Engelmann spruce (Picea engelmannii Parry ex Engelm.) exhibits cone crop periodicity, producing seed in a cyclic pattern. Variation in seed production has been noted between individuals of a population, but synchronization on a large scale is common. The theory that ultimately these periodic large cone crops have resulted from the selective pressures of seed and cone predators, referred to as the predator satiation hypothesis, is considered. Assuming predator pressures have operated over evolutionary time to select for periodic synchrony, associations between seed and cone predators and cone crop production levels were anticipated. These potential consequences of predator satiation were examined. Long-term data from 1948 to 1970 of Engelmann spruce cone production levels and small mammal populations, estimated from trappings, were analyzed for positive associations. Three small mammal categories, mice (Peromyscus spp.), chipmunks (Eutamias spp.) and red squirrels (Tamiasciurus hudsonicus) were examined. Only the correlation coefficient between population indices for mice and cone crop production was found to be significant. Engelmann spruce cones were collected throughout the summer of a year of low cone production. The impacts and timing of insect infestation were determined in developing cones. The major insects found were western spruce budworm (Choristoneura occidentalis (Freeman) (Lepidoptera: Torticidae)), fir coneworm (Dioryctria abietvorella (Grote) (Lepidoptera: Pyralidae)), and spruce seed moth (Laspeyresia youngana (Kearfott) (Lepidoptera: Olethreutidae)). Insects reduced the survival of cones to 11.48 cones out of 100. The high percentage of seeds and cones lost to insect predation supported previous studies of a similar nature. Both studies examined the potential consequences of the predator satiation hypothesis which has been suggested as an adaptive mechanism for trees to avoid seed and cone predation.

Failure of viable seed to germinate results in poor stands and often in lower yields. Some of the more important factors that affect germination of seed are temperature, moisture, aeration, and alkalinity.

A theoretical investigation of the factors that affect the population dynamics of annual plants growing in deserts was conducted through the use of computer modeling techniques. A series of three models of the yearly life cycle of desert annuals was constructed and their behavior examined. The dissertation centers around the third and most complex model, a computer simulation model with distinguishable seed cohorts in a randomly varying rainfall environment. A typical simulation run was for 80 years and cost $1.00. The five plant functions were (l} seed losses (mainly predation) as a function of seed age, (2) seed dormancy as a function of seed ages (3) percent germination of the non-dormant seeds in response to germinating rainfall, (4) percent survival from the seedling stage to maturity as a function of total rainfall over the growing season and seedling density, and (5) seeds produced per p 1 ant as a function of total rainfall over the growing season and density of mature plants. The stochasitc rainfall generator used historical rainfall probabilities from US Weather Bureau stations at Las Vegas, Nevada and Tucson, Arizona. The literature on desert annuals was carefully searched to provide supporting data for the plant functions used in the simulation model. Most of the data is for winter annuals growing on the Nevada Test Site near Las Vegas. Single species data are rare, so the model functions reflected the average plant responses for winter annuals as a group. This base run set of functions reproduced the observed data quite well. Sensitivity analysis of the simulation model indicated that in order to persist in the Las Vegas area, the seeds of annuals should have at least a one-year period of dormancy and a minimum threshold of about 15 mm of germinating rainfall. The age distribution of the seed reserves in the soil and the percent germinable is strongly influenced by the recent rainfall history of the site and the seed loss rate. The optimum balance is when the losses of older seeds from the seed reserves due to germination is the same size as the sum of the non-productive losses (e.g., predation). Several experiments are suggested -- some to cover gaps in the published data and some that became evident through the sensitivity analysis of the model itself.

Due to considerable loss through root-rot of mother beets while in storage during the winter of 1918-1919 the Amalgamated Sugar Company asked advice in regard to planting beets which had decay lesions on them. Would the beets yield seed if planted? How much seed would these beets yield as compared with healthy beets? Would the seed produced be injured by having been grown on decayed beets? It was felt that an experiment carried out with the above questions in view would bring out many facts upon which to base conclusions in answering the questions of the Sugar Company.

Alfalfa is one of the most valuable of our forage crops. A dependable source of seed is therefore a primary essential to the success of our present system of agriculture. More than 70 million pounds of alfalfa seed are required each year in the United States to maintain the present hay and pasture acreage of this crop; and the annual demand for seed would increase to more than 100 million pounds if the acreage were expanded to the extent recommended for soil conservation and a balanced agricultural security.

A series of experiments was conducted to: 1) investigate how feeding cattle with different amounts of different-sized seeds affects seed passage rate through the digestive tract, and the germinability of passed seeds; 2) examine how the location of seeds in dungpats of different thicknesses influences seedling emergence , development, and survival in cattle dungpats; and 3) characterize seedling emergence in naturally and artificially deposited cattle dungpats . Three perennial , cool-season grasses, bluebunch wheatgrass [Psuedoroegneria spicata (Pursh) A. Love], Sandberg bluegrass (Poa secunda Presl.), and 'Hycrest' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) X A. cristatum (L.) Gaert.], were used as representative revegetation species for the Intermountain West region. When cattle were fed 60,000, 30,000, 15,000, and 7,500 seeds of bluebunch wheatgrass and Sandberg bluegrass, the recovery of passed seeds for both species declined as seed feeding levels decreased from 60,000 to 7,500 seeds per animal and as time after seed ingestion increased from 1 to 4 days. Sandberg bluegrass seeds had greater germinability than bluebunch wheatgrass seeds at all seed feeding levels and collection dates. In complementary greenhouse studies, artificially prepared cattle dungpats (20 cm diameter) with different thicknesses (1, 2, and 4 cm) were placed on a sandy loam soil (initially at field capacity) in large plastic containers. Pre-germinated seeds of blue bunch wheatgrass, Sandberg bluegrass, and/or Hycrest crested wheatgrass were planted separately in the center and periphery of dungpats at heights (from bottom of dungpats) of 0.5 cm for 1-cm-thick dungpats, 0.5 and 1.5 cm for 2-cm-thick dungpats , and 0.5, 2.0, and 3.5 cm for 4-cm -thick dungpats. Half of the dungpat treatments received no supplemental water while the other half received additional water simulating a wet spring . After 60 days, seedling emergence, development , and survival for all species were greatest at the 0.5 cm planting height , regardless of dungpat thickness , and greatest in 1 cm-thick dungpats , regardless of planting height. Seedling emergence , development , and survival were greatest for Hycrest crested wheatgrass, followed by bluebunch wheatgrass and Sandberg bluegrass. In a field study, cattle dung containing passed seeds of blue bunch wheatgrass, Hycrest crested wheatgrass, and Sandberg bluegrass was formed into artificial dungpats (2 kg in mass) with thicknesses of 1, 2, and 4 cm, and respective diameters of 40, 28, and 20 cm, and deposited on bare soil. Cattle also deposited natural dungpats varying in mass, thickness, and diameter. Seedling emergence for all species decreased as artificial dungpat thickness increased from 1 to 4 cm, and was lowest in natural dungpats. Seedling emergence for all dungpat types was greatest for Hycrest crested wheatgrass, followed by Sandberg bluegrass and bluebunch wheatgrass. These studies indicate that: 1) cattle should be fed about 60,000 seeds ( of these grass species) per animal to pass sufficient germinable seed to establish at least one seedling in a dungpat; and 2) seedling emergence, development, and survival in cattle dungpats are greatly influenced by plant species (seeds) ingested, thickness of dungpats, seed location in dungpats, and moisture content of the soil underlying dungpats.