The relationship between morphological traits of the spring wheat spike and oviposition deterrence to orange wheat blossom midge

If morphological traits of a plant cause resistance to an insect pest or are strongly correlated with resistance levels, those traits can be used by plant breeders as phenotypic markers for indirect selection of resistance. To improve our understanding of antixenosis against the orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), expressed as oviposition deterrence in bread wheat, Triticum aestivum L. (Poaceae), 21 morphological traits of the wheat spike were studied in a genetically related wheat population and correlation of the traits with deterrence level was explored. The following traits had larger values in the deterrent parent of the population than the susceptible parent: ligule length, glume length, length of hair inside glume, palea length at post-anthesis stage, length of hair inside lemma, length of hair at spikelet base, inter-spikelet distance, and length of hair at rachis edge at post-anthesis stage. The highest correlation coefficient between mean egg density and a morphological trait of the wheat population was −0.287, which was for inter-spikelet distance. This represented 8% predictability from the point of view of crop breeding and explained one-twelfth of the variation in oviposition deterrence among lines. The morphological traits of bread wheat spikes were not highly correlated to deterrence. Therefore, no promising trait could be recommended for use in breeding programs. Studies of the fine-scale properties of the wheat plant surface, and their interactions with plant surface chemistry, with a greater focus on wheat midge oviposition behavior, may clarify the effect of the morphological traits on oviposition and deterrence.     

普通小麦：华山新麦草异代换系的选育及细胞遗传学研究

利用缺体小麦－华山新麦草七倍体杂种（２ｎ＝４９,ＡＡＢＢＤＤＮ）杂交,Ｆ１再瑟相应的缺体小麦回交２次,在ＢＣ２Ｆ１镜检选出２ｎ＝４１的植株,同时套代自交,选育出５Ａ和３Ｄ两种异代换系。单体找换植侏自交产生二体代换植侏的频率为２３．１６％。５Ａ代换植侏在减数分裂中期Ⅰ２１Ⅱ的出现频率平均为８４．５２％,３Ｄ代换植侏２１Ⅱ的出现频率平均为６２．６１％。异代换系均生长旺盛,结实正常,说明异染色体能较好地     

How does photorespiration modulate leaf amino acid contents? A dual approach through modelling and metabolite analysis

The aim of this work was to establish the quantitative impact of photorespiration on leaf amino acid contents. Attached leaves of wheat and potato were incubated for 30–40 min under defined conditions in which net CO₂ uptake (A) was manipulated by irradiance, ambient CO₂ or ambient O₂. The incubated portion of the leaf was sampled by a rapid‐quench method and photorespiratory flux (v_o) was modelled from the measured rate of net CO₂ uptake. In both wheat and potato, the ratio between glycine and serine showed a strong positive correlation with v_o. Aspartate and alanine correlated negatively with v_o but glutamate and glutamine showed less clear relationships. In potato, glutamate and glutamine did not correlate clearly with either A or v_o. In wheat, glutamine showed a general increase with A but no relationship with v_o, whereas 2‐oxoglutarate contents correlated positively with v_o and negatively with A. As a result, glutamine : glutamate and glutamine : 2‐oxoglutarate increased with net CO₂ uptake in wheat, observations that are attributed primarily to imperfect and variable coupling between the supply of NH₃ in primary nitrogen assimilation and the associated delivery of 2‐oxoglutarate to the chloroplast. A simple theoretical analysis is used to illustrate the potentially marked impact of primary nitrogen assimilation on leaf glutamine, even against a background of high rates of photorespiratory ammonia recycling.     

Pressure chamber measurements using two wheat leaves

Summary The most widely used technique of leaf water potential measurements is with the Scholander pressure chamber. Representative leaf water potential values require many determinations on individual leaves and this can be time consuming in large fields or experiments with multiple treatments. This paper describes a method of obtaining a mean value more rapidly, by using two leaves in the pressure chamber at the same time, but recording the end point of each leaf separately.     

Salicylic acid induced physiological and biochemical changes in wheat seedlings under water stress

Salicylic acid (SA) is an important signal molecule modulating plantresponses to stress. It is recently reported to induce multiple stresstolerancein plants including drought. An experiment was, therefore, conducted toascertain the effect of salicylic acid on the growth and metabolic profile ofwheat seedlings under water stress. Irrespective of the SA concentration(1–3 mM) and water stress, SA treated plants showed, ingeneral, a higher moisture content, dry mass, carboxylase activity of Rubisco,superoxide dismutase (SOD) activity and total chlorophyll compared to those ofuntreated seedlings. SA treatment, under water stress, protected nitratereductase (NR) activity and maintained, especially at 3 mM SAconcentration, the protein and nitrogen content of leaves compared to watersufficient seedlings. Results signify the role of SA in regulating the droughtresponse of plants and suggest that SA could be used as a potential growthregulator, for improving plant growth under water stress.     

Sucrose Utilization via Invertase and Sucrose Synthase with Respect to Accumulation of Cellulose and Callose Synthesis in Wheat Roots under Oxygen Deficiency

The sucrose cleavage by sucrose synthase (SuSy) and neutral invertase was studied in wheat roots (Triticum aestivum L.) subjected to hypoxia or anoxia for 4 days. By in situ activity staining, increased SuSy activity was observed in the tip region and stele of root axes while the activity of invertase decreased. Cellulose content significantly increased in hypoxically treated roots. The cellulose deposition was correlated with regions of high SuSy activity, being mainly located in the pericycle and endodermis. Invertase activity was distributed along the root without clear difference between cortex and stele. Under root hypoxia, a significant increase in the structural carbohydrates, callose and especially cellulose, was shown. Increasing levels of soluble carbohydrates were partially used to synthesize cellulose for secondary wall thickening and callose to counteract the tissue injury following low-oxygen stress. Under strict anoxia, the roots were much more injured but sustained a high level of cellulose and callose while the soluble carbohydrates almost disappeared.     

Subcellular localization of β-1,3-glucanase in Puccinia recondita f.sp. tritici-infected wheat leaves

An antiserum raised against the purified 33-kDa β-1,3-glucanase of wheat (Triticum aestivum L.) was employed to investigate the ultrastructural localization of the enzyme in wheat leaves infected with Puccinia recondita Rob. ex Desm. f.sp. tritici Eriks. and Henn. using a post-embedding immunogold labelling technique. In both compatible and incompatible interactions, β-1,3-glucanase was detected in the host plasmalemma and in the domain of the host cell wall near the plasmalemma of the mesophyll cells, but higher concentrations of the enzyme were detected in infected resistant wheat leaves than in infected susceptible ones. β-1,3-Glucanase was also found in the secondary thickening of xylem vessels and in the walls of guard cells, epidermal cells and phloem elements, while no labelling was observed in host organelles, viz. vacuoles, mitochondria, endoplasmic reticulum, Golgi bodies, nuclei and chloroplasts. A low concentration of the enzyme was detected on the intercellular hyphal wall and in the hyphal cytoplasm. In the compatible interaction, β-1,3-glucanase was demonstrated to accumulate predominantly in the haustorial wall and extrahaustorial matrix. In the incompatible interaction, strong labelling for β-1,3-glucanase was found in host cell wall appositions, in the extracellular matrix in the intercellular space, and in electron-dense structures of host origin which occurred in the incompatible interaction only. Received: 22 July 1997 / Accepted: 16 August 1997     

Influences of different nitrogen sources on nitrogen- and water-use efficiency, and carbon isotope discrimination, in C3 Triticum aestivum L. and C4 Zea mays L. plants

The impacts of various nitrogen sources, i.e. NO⁻ ₃, NH₄ ⁺ or NH₄NO₃ in combination with gaseous NH₃, on nitrogen-, carbon- and water-use efficiency and ¹³C discrimination (δ¹³C) by plants of the C₃ species Triticum aestivum L. (wheat) and the C₄ species Zea mays L. (maize) were studied. Triticum aestivum and Z. mays were hydroponically grown with 2 mol · m⁻³ of N supplied as NO⁻ ₃, NH₄ ⁺ or NH₄NO₃ for 21 and 18 d, respectively, and thereafter exposed to gaseous NH₃ at 320 μg · m⁻³ or to ambient air for 7 d. In T. aestivum and Z. mays over a 7-d growth period, nitrogen-use efficiency (NUE) values were influenced by N-sources in the decreasing order NH₄NO₃-N > NO⁻ ₃-N > NH₄ ⁺-N and NO⁻ ₃-N > NH₄NO₃-N > NH₄ ⁺-N, respectively. Fumigation with NH₃ decreased the NUE values of plants grown with any of the N-forms. During 28- and 7-d growth periods, N-sources affected water-use efficiency (WUE) values in the decreasing order of NH₄ ⁺-N > NO⁻ ₃-N≈NH₄NO₃-N in non-fumigated T. aestivum, while fumigation with NH₃ increased the WUE of NO⁻ ₃-grown plants. There were insignificant effects of N-sources on WUE values of Z. mays over 25- and 7-d growth periods. Furthermore, δ¹³C values in plant tissues (leaves, stubble and roots) were higher (less negative) in NH₄ ⁺-grown plants of T. aestivum and Z. mays than in those supplied with NH₄NO₃ or NO⁻ ₃. Regardless of the N-form supplied to the roots of the plant species, exposure to NH₃ caused more-positive δ¹³C values in the plant tissues. These results indicate that the variations in N-source were associated with small but significant variations in δ¹³C values in plants of T. aestivum and Z. mays. These differences in δ¹³C values are in the direction expected from differences in WUE values over long or short growth periods and with differences in the extent of non-Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase, EC 4.1.1.39) carboxylate contribution to net C acquisition, as a function of N-source. Received: 12 September 1997 / Accepted: 13 January 1998     

The Role of Hormones in Fast Growth Responses of Wheat Plants to Osmotic and Cold Shocks

The effects of nutrient-solution cooling and PEG addition to the nutrient solution on the phytohormone content, the rate of leaf growth, leaf extensibility under the influence of external mechanical action, osmotic potential, and transpiration were studied in seven-day-old wheat plants. Leaf growth rapidly ceased, and the transpiration rate was reduced in both treatments. Growth cessation induced by PEG was transient, and growth resumption was preceded by an increase in the leaf extensibility. The functional role of auxin accumulation in plant shoots in the control of extensibility as well as the relationship between the ABA accumulation and a decrease in the cytokinin content, on the one hand, and reduced transpiration, on the other hand, under stress conditions are discussed.