Thesis (Ph. D.)--Washington State University, December 2008. / Title from PDF title page (viewed on Jan. 22, 2009). "School of Biological Sciences." Includes bibliographical references.

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Climate change is one of the biggest challenges facing agriculture today. Transient or prolonged heat stress can be detrimental to plant reproductive development. The male gametophyte, pollen, is particularly sensitive to heat stress, resulting in sterile pollen (pre-anthesis) or deformed/stunted pollen tubes (post-anthesis). Quinoa (Chenopodium quinoa Willd.) has recently seen a rise in global interest due to its nutritional qualities, but global expansion of quinoa is partially hindered by its susceptibility to heat. It has been hypothesized that introgression of heat tolerance traits from wild relatives that occupy warmer environments can increase thermotolerance in quinoa. The goal of this research was to investigate the effect of heat stress on mature pollen grains from quinoa and its wild relatives, C. berlandieri and C. hircinum. To answer this question, several experiments were performed: 1. The nuclear number of the pollen of wild relatives was assessed to determine whether mature pollen grains were released at the trinucleate stage. All pollen was found to be trinucleate. 2. Pollen germination medium was optimized for four accessions: C. quinoa (QQ74; PI 614886), C. berlandieri var. zschackei (CB; BYU14118), and C. hircinum (CHA; Hircinum-069 and CHC; BYU17105). Optimal sucrose and PEG concentrations were determined to be: 5% sucrose/20% PEG for QQ74 and CB; 20% sucrose/0% PEG for CHA; and 10% sucrose/20% PEG for CHC. 3. Temperature optima for pollen germination for QQ74 was 32°C-36°C; CB was 30°C-34°C; CHA was 36°C; and CHC was 32°C -34°C. Overall, pollen from wild relatives was not found to be more heat-tolerant than pollen from domesticated quinoa. 4. Pollen tube elongation over time was observed for all four accessions at 34°C and 38°C, with CHA and QQ74 having the lowest decrease in rate at 38°C (35 and 45%, respectively). This study provides a new method for pollen collection for quinoa and its wild relatives, further optimizes the pollen germination media for QQ74, introduces pollen germination media for three wild accessions, and investigates the effect of heat stress on mature pollen grains. These observations can be employed in future studies investigating heat stress response of pollen in quinoa and its wild relatives.

Approximately 90% of flowering plants depend on pollinators for reproduction. The stability and effectiveness of plant-pollinator interactions are crucial for ecosystem function. Increasing numbers of non-native plants are naturalized in plant communities and may alter pollination success of native plant species. Thus, invasive species have the potential to alter community function and stability. However, the effects of invasive species on community-wide plant-pollinator interactions are poorly understood. While the effects of invasive species on the structure of plant-pollinator networks are well studied. However, these studies have relied on pollinator visitation data that is only one component of the pollination process. Thus, the effects of invasive species on pollen transport and pollen transfer dynamics remain unknown and this may misrepresent the true nature of invasive effects on community-wide plant-pollinator interactions. Pollen transport networks may give more accurate representations of plant-pollinator interactions by providing information on pollen collection by floral visitors. Therefore, in this study I evaluate the effect of the invasive Cirsium arvense on pollen transport networks to improve our understanding of the impact that invasive plants have on community-wide plant-pollinator interactions. Pollinators were collected on one invaded and one non-invaded site once weekly throughout the flowering season (May- August of 2017). Pollen was isolated for each insect and pollen samples were identified with a pollen reference library and counted using a hemocytometer. 154 insect morphospecies were collected carrying 73 pollen species. Preliminary results indicate that Cirsium arvense has no impact on network structure: connectance (0.15 and 0.18), link density (3.01 and 2.23), and weighted nestedness (0.68 and 0.75), for invaded and non-invaded respectively. However, the role of individual species within the network seems to vary between sites suggesting that Cirsium arvense may change community dynamics (identity of species-pair interactions). Future analysis will evaluate invasive species effects at the species level.

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Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1961 I57

LD2668 .T4 1962 S36

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

No description available.