Academic literature on the topic 'Pollen physiological function'

Methods of palaeoclimate reconstruction from pollen are built upon the assumption that plant–climate interactions remain the same through time or that these interactions are independent of changes in atmospheric CO2. The latter may be problematic because air trapped in polar ice caps indicates that atmospheric CO2 has fluctuated significantly over at least the past 400,000 yr, and likely the last 1.6 million yr. Three other points indicate potential biases for vegetation-based climate proxies. First, C3-plant physiological research shows that the processes that determine growth optima in plants (photosynthesis, mitochondrial respiration, photorespiration) are all highly CO2-dependent, and thus were likely affected by the lower CO2 levels of the last glacial maximum. Second, the ratio of carbon assimilation per unit transpiration (called water-use efficiency) is sensitive to changes in atmospheric CO2 through effects on stomatal conductance and may have altered C3-plant responses to drought. Third, leaf gas-exchange experiments indicate that the response of plants to carbon-depleting environmental stresses are strengthened under low CO2 relative to today. This paper reviews the scope of research addressing the consequences of low atmospheric CO2 for plant and ecosystem processes and highlights why consideration of the physiological effects of low atmospheric CO2 on plant function is recommended for any future refinements to pollen-based palaeoclimatic reconstructions.

Chickpea (Cicer arietinum L.), in its reproductive stage, is sensitive to heat stress (32/20°C or higher as day/night temperatures) with consequent substantial loss of potential yields at high temperatures. The physiological mechanisms associated with reproductive failures have not been established: they constitute the basis of this study. Here, we initially screened a large core-collection of chickpea against heat stress and identified two heat-tolerant (ICC15614, ICCV. 92944) and two heat-sensitive (ICC10685, ICC5912) genotypes. These four genotypes were sown during the normal time of sowing (November–March) and also late (February–April) to expose them to heat stress during reproductive stage (>32/20°C). The genotypes were assessed for damage by heat stress to the leaves and reproductive organs using various indicators of stress injury and reproductive function. In the heat-stressed plants, phenology accelerated as days to flowering and podding, and biomass decreased significantly. The significant reduction in pod set (%) was associated with reduced pollen viability, pollen load, pollen germination (in vivo and in vitro) and stigma receptivity in all four genotypes. Heat stress inhibited pollen function more in the sensitive genotypes than in the tolerant ones, and consequently showed significantly less pod set. Heat stress significantly reduced stomatal conductance, leaf water content, chlorophyll, membrane integrity and photochemical efficiency with a larger effect on heat-sensitive genotypes. Rubisco (carbon-fixing enzyme) along with sucrose phosphate synthase (SPS) and sucrose synthase (SS) (sucrose-synthesising enzymes) decreased significantly in leaves due to heat stress leading to reduced sucrose content. Invertase, a sucrose-cleaving enzyme, was also inhibited along with SPS and SS. The inhibition of these enzymes was significantly greater in the heat-sensitive genotypes. Concurrently, the anthers of these genotypes had significantly less SPS and SS activity and thus, sucrose content. As a result, pollen had considerably lower sucrose levels, resulting in reduced pollen function, impaired fertilisation and poor pod set in heat-sensitive genotypes.

The SWEET (sugars will eventually be exported transporter) family was identified as a new class of sugar transporters that function as bidirectional uniporters/facilitators and facilitate the diffusion of sugars across cell membranes along a concentration gradient. SWEETs are found widely in plants and play central roles in many biochemical processes, including the phloem loading of sugar for long-distance transport, pollen nutrition, nectar secretion, seed filling, fruit development, plant–pathogen interactions and responses to abiotic stress. This review focuses on advances of the plant SWEETs, including details about their discovery, characteristics of protein structure, evolution and physiological functions. In addition, we discuss the applications of SWEET in plant breeding. This review provides more in-depth and comprehensive information to help elucidate the molecular basis of the function of SWEETs in plants.

In many cases, patients allergic to birch pollen also show allergic reactions after ingestion of certain fruits or vegetables. This observation is explained at the molecular level by cross-reactivity of IgE antibodies induced by sensitization to the major birch pollen allergen Bet v 1 with homologous food allergens. As IgE antibodies recognize conformational epitopes, a precise structural characterization of the allergens involved is necessary to understand cross-reactivity and thus to develop new methods of allergen-specific immunotherapy for allergic patients. Here, we report the three-dimensional solution structure of the soybean allergen Gly m 4, a member of the superfamily of Bet v 1 homologous proteins and a cross-reactant with IgE antibodies originally raised against Bet v 1 as shown by immunoblot inhibition and histamine release assays. Although the overall fold of Gly m 4 is very similar to that of Bet v 1, the three-dimensional structures of these proteins differ in detail. The Gly m 4 local structures that display those differences are also found in proteins from yellow lupine with known physiological function. The three-dimensional structure of Gly m 4 may thus shed some light on the physiological function of this subgroup of PR10 proteins (class 10 of pathogenesis-related proteins) and, in combination with immunological data, allow us to propose surface patches that might represent cross-reactive epitopes.