Background and Aims High night temperatures are more harmful to grain weight in rice than high day temperatures. Grain growth rate and growth duration were investigated to determine which was the cause of the decrease in final grain weight under high night temperatures. Endosperm cell number and cell sizes were also examined to determine which might cause the decrease in final grain weight.Methods Rice plants were grown outdoors in plastic pots and moved at heading time to three temperaturecontrolled glasshouses under high night temperature (HNT; 22/34 C), high day temperature (HDT; 34/22 C) and control conditions (CONT; 22/22 C). Grains were sampled periodically, and the time-course of grain growth was divided into rate and duration by logistic regression analysis. Endosperm cell numbers and cell sizes were analysed by digitalized hand-tracing images of endosperm cross-sections.Key Results The duration of grain growth was reduced by high temperature both day and night. However, the rate of grain growth was lower in HNT than in HDT. The number of cells in endosperm cross-sections in HNT was similar to that in HDT, and higher than that in CONT. The average cell area was smaller in HNT than in either CONT or HDT. The differences in average cell areas between HNT and HDT were greater at distances 60-80 % from the central point of endosperm towards the endosperm surface.Conclusions The results show that HNT compared with HDT reduced the final grain weight by a reduction in grain growth rate in the early or middle stages of grain filling, and also reduced cell size midway between the central point and the surface of endosperm.ª 2005 Annals of Botany Company

No abstract

In this report, we developed the pressure probe electrospray ionization-mass spectrometry with internal electrode capillary (IEC-PPESI-MS) which enables high spatial-resolution cell sampling, precise postsampling manipulation, and high detection sensitivity. Using this technique, a comparative in situ single-cell metabolite profiling of stalk and glandular cells, the two adjacent cell types comprising a trichome unit in tomato plants (Solanum lycopersicum L.), were performed to clarify the extent of metabolic differentiation between two cell types as well as among different types of trichomes. Owing to high sensitivity of the system, less than a picoliter cell sap from a single stalk cell sufficiently yielded a number of peaks of amino acids, organic acids, carbohydrates, and flavonoids. The minimal cell sap removal from a stalk cell without severe disturbance of trichome structure enabled sequential analysis of adjacent glandular cell on the same trichome, which showed the presence of striking differences in metabolite compositions between two adjacent cell types. Comparison among different types of trichome also revealed significant variations in metabolite profiles, particularly in flavonoids and acyl sugars compositions. Some metabolites were found only in specific cell types or particular trichome types. Although extensive metabolomics analysis of glandular cells of tomato trichomes has been previously documented, this is the first report describing cell-to-cell variations in metabolite compositions of stalk and glandular cells as well as in different trichome types. Further application of this technique may provide new insights into distinct metabolism in plant cells displaying variations in shape, size, function and physicochemical properties.

Rice (Oryza sativa L.) grain yields in western Japan have recently decreased as a result of higher temperatures during ripening. The improvement of rice cultivars for stable production is a pressing need because of climate change. In this study, the features of good ripening of the new rice cultivar Nikomaru were analyzed through a 3‐yr field experiment. Nikomaru showed a yield increase of 7 to 8% compared with the leading cultivar in western Japan, Hinohikari, even though these cultivars have similar source size (available carbohydrate during ripening) and sink size (total spikelet number and rough grain size). The greater ripening index (percentage of ripened grains × 1000‐grain weight) in Nikomaru, which determined the varietal yield differences in this study, was attributed to the translocated dry matter for ripening (ΔT) but not to the newly assimilated dry matter during ripening (ΔW). In addition, ΔT was positively correlated with the nonstructural carbohydrate content in the stem at full heading (NSCh). There was positive correlation between the NSCh and the percentage of ripened grains in the hotter years (2005 and 2007). It was suggested that a large NSCh as the main source of the ΔT contributes to the maintenance of a higher ripening rate especially under high temperatures.