Ripe pollen carbohydrate changes in Trachycarpus fortunei: the effect of relative humidity

Abstract

Pollen of the palm Trachycarpus fortunei was kept at 25°C and relative humidities (RH) of 20, 55 and 98%. Changes in viability, water content and carbohydrates were measured over 2-17 days. Water content remained almost constant at 20 and 50% RH and increased dramatically at 98%. Pollen viability and germination rate remained almost constant over 14 days at 20% RH and decreased to about 2% after 7-9 days at 55% and to even less at 98% RH. Although the three experimental conditions were constant, qualitative and quantitative variations in pollen carbohydrates were recorded, even after pollen had lost its viability. The quantities of mono-, di-and polysaccharides varied with the period of pollen storage at the various RH. The greatest changes in glucose, fructose and sucrose content were recorded at 55 and 98% RH. At these relative humidities, maximum glucose and fructose content and minimum sucrose content occurred at maximum water content. Starch was not present in mature pollen but appeared and peaked after 7-9 days of pollen storage at 55 and 98%. Appearance of starch coincided with an increase in pectin content. PAS-positive cytoplasmic polysaccharides showed an increasing trend at 20% RH. A relation was found between pollen viability, water content and monosaccharide content. Pollen viability and germination capacity remained high at 20% RH for 14 days. At this relative humidity, pollen water, glucose and fructose contents remained almost constant, while sucrose reached its maximum value. The fluctuations of more complex carbohydrates (starch, pectins and PAS-positive cytoplasmic polysaccharides) were less easy to interpret. Changes observed under experimental conditions could simulate processes occurring in nature during pollen presentation and dispersal.

Pollen Developmental Arrest: Maintaining Pollen Fertility in a World With a Changing Climate

“…Accumulation of soluble carbohydrates such as sucrose plays a role in membrane stabilization and protection against osmotic stress (Speranza et al, 1997; Hoekstra, 2002, 2005; Pacini et al, 2006). Variation in temperature and relative humidity in the environment affects carbohydrate accumulation, rate of dehydration and pollen viability (Guarnieri et al, 2006; Carrizo-García et al, 2010, 2014). Ripe pollen grains can be starchy or starchless, but there is always a variable proportion of soluble and insoluble cytoplasmic carbohydrates (Table 1).…”

Pollen performance, cell number, and physiological state in the early-divergent angiosperm Annona cherimola Mill. (Annonaceae) are related to environmental conditions during the final stages of pollen development

“…All this suggests that metabolic activity is arrested in pollen from detached anthers and, consequently, mitosis II and starch hydrolysis do not take place. Starch hydrolysis is related to protection against desiccation (Speranza et al 1997), and recent studies have demonstrated the association between the maintenance of pollen viability and the maintenance of low moisture content and high levels of sucrose and total insoluble cytoplasmic carbohydrates (Guarnieri et al 2006;Nepi et al 2010). In fact, at anther dehiscence, bicellular pollen usually shows lower metabolic activity and lower water content than tricellular pollen, which allows for better storage of bicellular pollen at low temperatures (Barnabas and Kovacs 1997).…”

The impact of plant and flower age on mating patterns

“…Low relative humidity has also been shown to reduce pollen longevity in species with desiccation-intolerant pollen such as Zea mays (Buitink et al, 1996;Fonseca and Westgate, 2005) and Pennisetum glaucum (Kumar et al, 1995), although this was not true of the dessication-tolerant pollen from Typha latifolia (Buitink et al, 1996). Conversely, increased pollen longevity with lower relative humidity was observed in the palm Trachycarpus fortunei (Guarnieri et al, 2006) and in Pinus taeda (Bohrerova et al, 2009). These data suggest that timing of flowering within a season could have a large impact on reproductive success when water availability is variable.…”