Effects of pollen supply and quality on seed formation and maturation in Pinus densiflora

Abstract

To understand the detailed mechanisms underlying variations in seed productivity per cone, it is important to examine simultaneously the effects of two pollination mode components (pollen supply and quality) on two seed production processes (seed formation and maturation). We conducted artificial pollination experiments with four pollination treatments (selfing, polycross, no-pollination and open-pollination treatments) in each of two vertical crown layers (upper and lower) for 19 Pinus densiflora ramets. We measured formed seeds as a proportion of ovules (P(Form)), and filled seeds as a proportion of formed seeds (P(Fill)) per cone in each treatment and layer, and inferred the relative influences of pollination mode and resource availability on seed productivity. In the no-pollination treatment, no seeds were formed in any cones of all five ramets. The Generalized Linear Model showed that there were no significant differences in P(Form) both between selfing and polycross treatments and upper and lower layers. The mean P(Fill) values in the selfing treatment were significantly lower than those in the polycross treatment in both layers. The mean P(Fill)s of the two layers did not differ significantly in the selfing treatment, but did in the open-pollination and polycross treatments. The results show that pollen supply affects mainly seed formation, whereas pollen quality affects mainly seed maturation. Resource availability also affects mainly seed maturation, if pollen quality is higher than a certain threshold.

Seed production and dispersal limit treeline advance in the Pyrenees

“…We did not find a reduction in the proportion of full seeds with elevation, which would be the first negative outcome of selfing in other Pinus species (Iwasaki et al, 2013). Contrarily, our results suggest that seed development on the Pinus uncinata alpine treeline could be more influenced by low pollen supply at higher elevations (Iwaizumi & Takahashi, 2012). The decrease in the production of full seeds found along the gradient in our study sites is not accompanied by a reduction in the number of cones produced per tree (see Appendix ), nor in the weight of the seeds or in their viability.…”

Pollen limitation failing reproductive success in selected animal pollinated trees of tropical moist deciduous forest of north-eastern hill region, India

“…Pollen quantity and quality provide in measuring and forecasting several factors, e.g. crop yield in trees (Allison, 1990;Hirayama et al, 2005;Iwaizumi & Takahashi, 2012) and yield in agriculture crops (Westgate et al, 2003), fruit size and production of seeds (Faegri & Iversen, 1989;McKone, 1990;Baskin & Baskin, 2018), ancient and current vegetation (Moore et al, 1991;Rogers, 1993;Obigba, 2021) and respiratory allergy symptoms from specific taxa to human beings (Filon et al, 2000;Gioulekas et al, 2004;Damialis et al, 2011;Sousa-Silva et al, 2021). In the present study the amount of pollen produced by individuals of selected five species was considered as pollen quantity which can be consumed by the animals and can be lost to the environment (through abiotic factors).…”

Geographical cline and inter‐seaside difference in cone characteristics related to climatic conditions of old planted Pinus thunbergii populations throughout Japan

“…In a physiology study for P. densiflora , a 50% reduction in photosynthetic photon flux density (PPFD) caused a 10% to 15% reduction in net photosynthetic rate ( V cmax ; calculated from regression coefficients by Han, Kawasaki, Katahata, & Chiba, 2003). As costs for cone construction are much greater than those for seed production within the cone (Iwaizumi et al, 2008; Iwaizumi & Takahashi, 2012), the larger investment per cone in populations likely to have lower resource availability would achieve higher seed productivity per cone development cost in terms of resource‐use efficiency (Iwaizumi et al, 2019). The larger cones and higher seed productivity per cone found in trees of populations on the Japan Sea side could be due to adaptive or plastic responses that increase reproductive success by maximizing the number of seeds in a smaller number of cones.…”

“…Some previous studies have suggested that cone variation, such as cone size or thickness of scales in Pinus , should have adaptive significance as a means to maintain seed production and may be the responses to protect against snowfall or low temperature (Farjon & Styles, 1997; Gil et al, 2002; Linhart, 1978). As cone development carries a high cost to achieve seed production (Despland & Houle, 1997; Goubitz, Werger, Shmida, & Ne'eman, 2002; Iwaizumi & Takahashi, 2012), producing relatively highly reproductive cones is important for maximizing reproductive success in consideration of the development cost, particularly in environments with low temperature, less solar irradiance or less sunshine (Iwaizumi, Ohtani, & Takahashi, 2019). If environmental factors impact cone morphology, geographical variation linked to key influential climate differences is expected among populations or regions.…”