maximum grain size. A growth chamber study by Badu-Apraku et al. (1983) shows a more dramatic yield loss The average temperature in the U.S. Corn Belt during the grainassociated with high temperatures during the period of filling period of maize (Zea mays L.) is above optimum for maximum grain yield. The objectives of this study were to determine the effects grain filling . They observed a 42% loss in grain weight of an extended period of high temperature during grain filling on per plant when day/night temperature from 18 d postkernel growth, composition, and starch metabolism of seven maize silking to maturity was increased from 25/15 to 35/15ЊC, inbreds. Plants were exposed to heat stress (33.5/25؇C) or control (25/ a6 ЊC rise in average daily temperature. 20؇C) day/night temperature treatments in a greenhouse from 15 dThe interaction of heat stress with other environmenafter pollination (DAP) until maturity, and the experiment was contal factors in the field, such as drought stress, makes it ducted in triplicate over time. Root zone temperature was maintained difficult to study the effect of high temperature on maize at 25/20؇C in both treatments. No significant interaction occurred yield in isolation. Furthermore, it may be difficult to between genotype and temperature treatments for nine grain traits. separate the effects of heat stress occurring during grain Heat stress lengthened the duration of grain filling on a heat unit filling from a previously occurring heat stress. The use (HU) basis, but an overcompensatory reduction in kernel growth rate per HU resulted in an average mature kernel dry weight loss of 7% of controlled environments makes it possible to study (P ϭ 0.06). Proportionally similar reductions occurred for starch, more precisely how high temperature treatment affects protein, and oil contents of the kernel. Heat stress also reduced kernel maize grain filling. However, controlled-environment density. A survey of 11 enzymes of sugar and starch metabolism studies should strive to mirror conditions in the field as extracted from developing endosperm revealed that ADPglucose pyclosely as possible. As described below, conditions of rophosphorylase, glucokinase, sucrose synthase, and soluble starch root temperature and photyosynthetically active radiasynthase were most sensitive to the high temperature treatment. Howtion (PAR) intensity can differ between the field and ever, upon adjusting enzyme activities with measured temperature controlled environment and have been shown to be coefficients (i.e., Q 10 ), only ADPglucose pyrophosphorylase exhibited important factors that help determine how plants rereduced activity. Results indicate that chronic heat stress during grain spond to high temperature.filling moderately restrains seed storage processes and select enzymes of starch metabolism to similar degrees across multiple maize inbreds.

Endophytic bacteria are ubiquitous in most plants and colonise plants without exhibiting pathogenicity. Studies on the diversity of bacterial endophytes have been mainly approached by characterisation of isolates obtained from internal tissues. Despite the broad application of culture-independent techniques for the analysis of microbial communities in a wide range of natural habitats, little information is available on the species diversity of endophytes. In this study, microbial communities inhabiting stems, roots and tubers of three potato varieties were analysed by 16S rRNA-based techniques such as terminal restriction fragment length polymorphism analysis, denaturing gradient gel electrophoresis as well as 16S rDNA cloning and sequencing. Two individual plant experiments were conducted. In the first experiment plants suffered from light deficiency, whereas healthy and robust plants were obtained in the second experiment. Plants obtained from both experiments showed comparable endophytic populations, but healthy potato plants possessed a significantly higher diversity of endophytes than stressed plants. In addition, plant tissue and variety specific endophytes were detected. Sequence analysis of 16S rRNA genes indicated that a broad phylogenetic spectrum of bacteria is able to colonise plants internally including alpha-, beta-, and gamma-Proteobacteria, high-GC Gram-positives, microbes belonging to the Flexibacter/Cytophaga/Bacteroides group and Planctomycetales. Group-specific analysis of Actinomycetes indicated a higher abundance and diversity of Streptomyces scabiei-related species in the variety Mehlige Mühlviertler, which is known for its resistance against potato common scab caused by S. scabiei.

Endophytes are nonpathogenic plant-associated bacteria that can play an important role in plant vitality and may confer resistance to abiotic or biotic stress. The effects of 5 endophytic bacterial strains isolated from pepper plants showing 1-aminocyclopropane-1-carboxylate deaminase activity were studied in sweet pepper under in vitro conditions. Four of the strains tested showed production of indole acetic acid. Plant growth, osmotic potential, free proline content, and gene expression were monitored in leaves and roots under control and mild osmotic stress conditions. All indole acetate producers promoted growth in Capsicum annuum L. 'Ziegenhorn Bello', from which they were isolated. Osmotic stress caused an increase in the content of free proline in the leaves of both inoculated and noninoculated plants. Inoculated control plants also revealed higher proline levels in comparison with noninoculated control plants. Differential gene expression patterns of CaACCO, CaLTPI, CaSAR82A, and putative P5CR and P5CS genes during moderate stress were observed, depending on the bacterium applied. Inoculation with 2 bacterial strains, EZB4 and EZB8 (Arthrobacter sp. and Bacillus sp., respectively), resulted in a significantly reduced upregulation or even downregulation of the stress-inducible genes CaACCO and CaLTPI, as compared with the gene expression in noninoculated plants. This indicates that both strains reduced abiotic stress in pepper under the conditions tested.

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