SUMMARYAt high northern latitudes, growing seasons are short with long days. In these conditions, tillering is an unwanted trait in barley (Hordeum vulgare L.), because the grains on tillers develop later than those on the main stem and are often harvested before they are fully mature, leading to reductions in overall quality. Hence, the uniculm growth habit has been considered an interesting option for boreal barley production. The aim of the present study was to determine the differences in the yield formation of conventional tillering and uniculm barley, using two pairs of near-isogenic lines and two controls. Uniculm and conventional tillering barley were grown in three experiments conducted at Suitia Experimental Farm, University Helsinki, Finland during 1999–2001. Samples were collected frequently to monitor the biomass and leaf area accumulation. Water-soluble carbohydrate content was analysed at anthesis and at maturity in different plant parts. At maturity, the numbers of spikes/plant and grains/spike were calculated and grain yield weighed. The grain yield of the uniculm barleys was stable over these growing seasons, but it was only half that of the conventional barley cultivars due to the absence of spike-bearing tillers, lower spike grain number and spike weight. In addition, the ability to transport photosynthesized carbohydrates to grains may have been reduced. Thus, it seems that uniculm barleys do not provide further improvement in barley yield.

Water is the primary regulator of yield formation in cereals. The effect of water limitation and its timing on development of yield components were studied in detail at spike and spikelet level in spring barley (Hordeum vulgare L.). An experiment with three watering treatments (control watering, CONT; drought prior to pollination, DR1 and terminal drought, DR2) was set up in a large greenhouse (20 x 30 m). In addition to watering treatments, two NPK fertilizer application rates (0 and 120 kg N ha-1) were used to investigate the fertilizer effect. The drought effect exceeded the effect of fertilizer application for grain number and single grain weight (SGW). DR1 reduced the number of grains, whereas DR2 reduced both SGW and the number of grains. Resuming the watering at pollination (DR1) restored photosynthesis and enhanced grain filling, resulting in almost similar SGW in DR1 and CONT plants. Spikelets in the upper mid-section of the spike dominated yield formation in all treatments. This was particularly emphasised in DR1 plants as 58 % of the grain yield was produced in spikelets 3-5, whereas in DR2 and CONT plants it was 39 % and 36 %, respectively. Hence, drought prior pollination strongly reduced yielding capacity (=grain number) in apical and basal spikelets. DR1 and DR2 reduced substantially grain yield and grain N yield resulting in low nitrogen use efficiency.

The Finnish growing season is particularly short, with an intensive growth period, unfavourable rainfall distribution and frequently occurring fluctuations in climate that affect crop growth and yield formation. A three-year study was conducted in the field to determine the contribution of alterations in canopy structure, tillering and stem elongation among dwarf (D), semidwarf (SD) and tall (T) oat (Avena sativa L.) lines to yield formation. Yield components, leaf characteristics and straw traits were measured from six oat lines (D lines Pal and Grane, SD lines Hja 76416 and Salo, and T lines Veli and Jalostettu maatiainen) separately on the main shoot and tillers. Results indicated that long leaf area duration and high leaf area index were associated with increased grain yield probably due to more persistent and active assimilation. Also, higher number of leaves increased the grain yield. Higher peduncle, straw and node weights associating with increased grain yield may result from more abundant assimilate reserves; however, the longer the straw and peduncle, the lower the grain yield, which may result from increased lodging of SD and T lines. The traits contributing most to the grain yield varied greatly from year to year. It is concluded that no single dominant trait determined grain yield, since yield is a product of several different traits. SD lines seemed to be most promising for further breeding programs on the basis of their growth pattern and yielding ability.;

To determine whether ABA accumulation inhibits or promotes shoot growth under stress, an ABA‐deficient mutant tomato, sitiens, and its wild‐type, the cultivar Rheinlands Rhum, were exposed to moderate salinity stress. Plants were grown at 75 mM NaCl for 2 weeks under conditions of moderate or high relative humidity (70% and 95% RH, respectively). At 70% RH, shoot DW and relative growth rate were reduced more in sitiens than in the cultivar, but the major difference between genotypes was in the degree of injury suffered by older leaves. Most leaves of sitiens died after 2 weeks, but those of the cultivar remained alive. When plants were grown at 95% RH, to maximize the leaf water status of both genotypes, there was no significant effect of salt on shoot DW of either genotype. However, there was still considerable leaf death in sitiens whereas no visible injury appeared in the cultivar. Cl– accumulated to higher levels in leaf tissues than Na+, but to similar concentrations in both genotypes, and so could not explain the injury in the sitiens leaves. The results indicate that ABA maintains rather than inhibits new growth under stress, and has a major effect on preservation of older leaves.

The effect of foliar-applied glycinebetaine (GB) on chloroplast ultrastructure, the amount of chlorophyll and proteins and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity in stressed tomato leaves were analysed. Initial, and total activity and activation state state of RuBPCO were also measured. RuBPCO activities, chloroplast area, and the number of plastoglobuli remained unaffected, while the relative area of starch granules increased in GB-treated, salt-stressed tomato leaflets. Under drought-stress, the relative area of plastoglobuli increased upon GB application. The primary effect of GB was, however, the increased protein and chlorophyll content.

Glycinebetaine is thought to act in many organisms as a compatible osmotic solute and/or osmoprotectant in cells suffering from high or low temperature, water deficiency and/or high salinity. The response of processing tomato plants to foliar-applied glycinebetaine (Greenstim) purified from sugar beet was studied in timing and dose field trials over two years. The highest yield increases obtained with a single application of glycinebetaine were up to 30% in Australia and 50% in Spain. The yield increment was more evident in reduced irrigation conditions. Plants treated with glycinebetaine yielded more fruits than untreated plants.

The effect of foliar application of glycinebetaine (50 and 100 mM) on photosynthesis, stomatal conductance, photorespiration and transpiration in tomato cv. Bos 3155 (Lycopersicon esculentum Mill.) and summer turnip rape cv. Kulta (Brassica rapa L. ssp. oleifera) plants subjected to drought and salinity are reported. Glycinebetaine application increased net photosynthesis of stressed plants. This was mostly due to increased stomatal conductance following glycinebetaine application as there were no marked changes in light and CO2 saturated rates of O2 evolution. Moreover, glycinebetaine application resulted in a significant decrease of photorespiration both in drought‐ and salt‐stressed plants.

Tomato (Lycopersicon esculentum Mill.) was used as a model system for investigating the effects of glycinebetaine applications on plants, as this species is unable to synthesise glycinebetaine, but is sensitive to exogenous supply. Glycinebetaine application significantly increased stomatal conductance of tomato plants grown in well-watered, water-deficient or saline conditions; however, glycinebetaine did not affect the leaf ABA concentration, relative water content, sap osmotic potential, or shoot water potential. Glycinebetaine applied to the foliage was readily absorbed, but the concentrations in the leaves made a negligible contribution to the total leaf sap osmotic potential. Our results indicate that applied glycinebetaine was involved in regulation of stomatal conductance but not via ABA metabolism or water relations. Glycinebetaine may have been accumulated in specific cells or cellular compartments, with consequences for stomatal functions. Further work is required to elucidate the cellular and subcellular localisation of applied glycinebetaine.

Wild rice (Zizania palustris L.), an aquatic grass that grows naturally in lakes and slowly flowing rivers in North America, has been used as a food for thousands of years by some aboriginal tribes. In natural stands, the seeds mature in the autumn and overwinter on the lake bed. They germinate in May, with growth to maturity requiring approximately 100 days. The similarity of growing conditions between North America and Finland suggests that wild rice might succeed in northern Europe. The wild rice plant and the production of both organically grown Canadian wild rice and paddy-grown wild rice in the USA are briefly described in this review article together with the results of preliminary growth trials and an assessment of its agricultural role in Finland.

Glycinebetaine, a novel product from sugar beet (Beta vulgaris L. v. altissima), is purified from molasses during sugar processing through chromatographic separation, enrichment and crystallisation. Glycinebetaine is environmentally safe, non-toxic and water-soluble and is found in animal, microbe and plant cells. Most halophytes, when grown under stress, synthesise glycinebetaine in their chloroplasts and accumulate it as an osmoprotectant. Here we show that foliarly applied glycinebetaine offers a new possibility to stabilise crop production under field conditions: fruit yield of tomato plants (Lycopersicon esculentum Mill.) grown in saline soils or exposed to high temperatures in California increased up to 39% when glycinebetaine was applied during midflowering. Similarly, glycinebetaine treatment of tomato plants in a commercial vegetable producer's greenhouse in Southern Finland increased the yield and the number of tomato fruits. In a separate greenhouse experiment, we showed that glycinebetaine application increased the rate of net photosynthesis of adequately watered and salt stressed tomato plants.

This study compares the response of old and modern oat (Avena sutiva L.) lines to pre-anthesis precipitation in long-term field trials, and to pre- and post-anthesis drought in the greenhouse. Long-term field trials were carried out at the Experimental Farms of Hankkija Plant Breeding Institute and the University of Helsinki between 1965 and 1988. Grain yield of 12 oat lines (released since 1959) was compared with that of the check lines. The effect of differences in May-June precipitation on grain yield was established for different lines. Greenhouse experiments included 19 oat lines (released since 1921) and three wild species of oat (A. barbata L., A. sterilis max. L. and A. fatua L.). The data from greenhouse experiments were analysed using discriminant analysis in groups of old (released before 1970s), modern, and wild oat types. Ranking of the oat lines according to results from long-term field trials and greenhouse experiments was not consistent; contrary to the field experiments, the old lines tended to be the most drought sensitive when tested in the greenhouse. Therefore, the simple and non-laborious methods used in this study for ranking of drought sensitivity of oat lines are not recommended.

Crop losses caused by environmental stresses might be reduced by applying osmoprotectans to crop canopies. Glycinebetaine is endogenously accumulated by some halophytes under stress conditions and represents such a compound. Glycinebetaine was applied exogenously to barley (Hordeum vulgare L.), oat (Avena sativa L.), spring wheat (Triticum aestwum L.), and summer turnip rape (Brassica rapa ssp. oleifera DC.) canopies and its optimal concentration was monitored in the greenhouse. In field experiments the response of crop plants to betaine applications was assessed by measuring accumulation of above ground biomass, leaf area index (LAI), leaf chlorophyll, and yield. The optimum betaine concentration producing advantageous effects on growth and crop physiology in turnip rape was close to 0.1 M and for wheat 0.3 M. Such concentrations promoted accumulation of betaine similar to that of halophytes under stress conditions [ca. 200 μmol (g DM)−1]. In the 1993 field experiment peak LAIs were recorded in irrigated wheat and barley treated with 17.5 kg ha−1 betaine applied at 300 1 ha−1. Green leaf area was slightly more persistent in wheat treated twice with 1 kg ha−1 betaine applied at 200 1 ha−1 in 1994, although it was not associated with increased grain yield. Our results indicated that betaine has no actual potential in Finland for the principal grain crops but further studies are needed in stress prone environments to assess the potential of betaine treatments for preventing crop failures.

Development of a dwarf oat (Avena sativa L.) for northern growing conditions may further improve many important agronomic features of the oat crop including lodging resistance, yield stability, yield potential, grain-straw ratio, and fertile tillering. Our objective in this study was to assess the performance of a Minnesota-adapted dwarf line at high latitudes, through measurement of several traits that characterize duration of pre- and post-anthesis growth and plant stand structure, with special reference to tiller growth and tiller productivity. Response of the dwarf line to seeding rate (250, 500, and 750 viable seeds m−2) and nitrogen fertilizer application rates (80, 120, and 160 kg N ha−1) was compared with that of a semi-dwarf line, a conventional height cultivar, and a landrace cultivar, all of which are adapted to long-day conditions. The experiments were conducted in Finland (60°13′N) in 1993 and 1994. The dwarf line produced less grain (≤ 30%) than the other lines but out-yielded the lodging-sensitive landrace in 1994 at a high seeding rate and high rate of nitrogen fertilizer application. As for the semi-dwarf line and conventional height line, the dwarf line produced the highest grain yield at 500 seeds m−2 which is the standard planting density for oat in Finland. The particularly short duration of the generative phase and associated low number of grains per main shoot panicle are likely to be principal contributors to low mean panicle-filling rate, panicle weight, and grain yield of the dwarf line. However it was better able to tiller and produce head-bearing tillers than the other lines. This increased number of tillers was, however, unable to compensate for yield reduction resulting from low yield potential of the main shoot. Key words:Avena sativa L., oat (dwarf), grain yield, landrace, partitioning, straw length, yield components

Several methods have been developed to assess differences in cultivar response to drought. This study consisted of 19 oat (Avena sativa L.) cultivars and breeding lines and three species of wild oats, and focused on comparison of several physiological screening methods -CO2 exchange rate (CER), stomatal conductance, stomatal resistance, disparity between air and leaf temperatures, accumulation of abscisic acid (ABA) and proline, and relative water content (RWC) - with yield losses. Early drought, occurring at four-five leaf stage or close to pollination date resulted in significantly reduced above-ground vegetative biomass and panicle weight. Reductions in panicle weight due to drought were greater than those in vegetative phytomass, which resulted in decreased harvest index (HI). Drought stress significantly increased stomatal resistance and accumulation of ABA and proline, whereas stomatal conductance, disparity between air and leaf temperatures and RWC, decreased owing to water deficit. Comparison of screening methods by calculating drought tolerance indices showed that none of the indices was associated with degree of yield losses. However, photosynthetic characters correlated with RWC both at early growth stages and close to pollination. Therefore, further studies that profoundly evaluate the relationship between these screening methods and degree of yield losses are needed.

Several methods have been developed to assess differences in genotypic response to drought. This study consisted of 19 oat (Avena sativa L. ) lines and three species of wild oats (Avena fatua, A. sterilis, and A. abyssinica) and focused on comparison of several physiological screening methods with yield losses. Early drought, occurring at 4–5 leaf stage, or close to pollination resulted in significantly reduced vegetative phytomass, panicle weight, and harvest index. Drought stress significantly increased stomatal resistance and accumulation of ABA and proline, whereas disparity between air and leaf temperatures and relative water content (RWC) decreased due to water deficit. Comparison of screening methods by calculating drought tolerance indices, showed that none of the indices were associated with degree of yield losses. However, photosynthetic characters correlated with RWC both at early growth stages and close to pollination. Hence, further studies that evaluate profoundly the relationship between these screening methods and degree of yield losses are needed.