The aim of studies was to identify how different morphological and biological characteristics influence spring barley (Hordeum vulgare L.) competitiveness against weeds in various organic and conventional farming locations. Do those traits have an influence on the yield and in which growing conditions the selection of genotypes for organic farming should be done? The plant traits related to competitiveness against weeds at the beginning of the vegetation period are important in breeding for organic agriculture. Ten different varieties were included in trials for three years in two organic and two conventional environments. The included varieties were divided in four groups with respect to time of release and adaptation to growing environments: old extensive varieties and landraces for low input agriculture, medium old varieties with good adaptation to unfavourable conditions, modern varieties for low input, and modern varieties for high input conditions. Results showed that such traits as productive tillering ability, development speed and plant height at the beginning of stem elongation stage provide good soil shading. The most of traits were negatively related to the grain yield. Selection of genotypes for traits which influence spring barley competitiveness against weeds, such as a growth habit in the tillering stage, development speed in tillering stage, plant height at the beginning of stem elongation, length of flag leaf and the width of flag leaf, and the plant height before harvest, may take place in conventional conditions as well as in organic conditions.

The lily (Lilium L.), a vegetative propagated perennial crop, is one of the economically most important flower bulb plants. It is cultivated worldwide as a cut flower, garden plant and pot plant. Lilies, 'the aristocrats of the garden', are very popular for their elegant flowers and stately habit, and offer the gardener an enormous range of colours, forms, and fragrances. The aim of this research was to evaluate the parent plants with the hybrids according to their morphological characteristics: plant height, flower diameter and inflorescence: number of flowers. In a trial, fourteen cross combinations were analyzed in 2006 – 2007. The evaluation was conducted in a lily breeding and growing farm 'Puķulejas', located in Saulkrasti, region of Riga, Latvia. The results showed that, if there were no significant differences in plant height between the parent plants, the hybrids were shorter than their parents. Male parents with short stems produced hybrids with shorter stems. Parental selections of medium and large number of flowers produced hybrids with comparatively large numbers of flowers on a stem, but if parents of different number of flowers were selected, in hybrids the smaller count dominated or prevailed.

Prolonged summer drought periods are forecasted for the Baltic Sea region during the 21st century, thus increasing the risk of drought stress of saplings used in forest regeneration. Nevertheless, the vitality of young stands might be increased by the selection of suitable planting material. The aim of this study was to estimate the effect of changes in distribution of summer precipitation on height increment, biomass distribution and root morphology of Scots pine and silver birch planting material commonly used in the forest regeneration in Latvia. Containerized pine and bare rooted birch saplings, planted in three different soil types, were subjected to altered distribution of summer precipitation, provided by the use of automated shelter. Sheltered saplings were weekly irrigated with the sum of precipitation of a corresponding period, while afield planted saplings had an unchanged precipitation regime and served as control. Height increment was measured once per week and estimation of morphology of saplings was done after the end of every vegetation season. Significant (p is less than 0.05) differences in height increment, and shoot and root biomass were observed among the same planting material in different irrigation regimes and soil types. In the control plots of peat soil, pine had a significantly (p is less than 0.05) larger height increment while birch-significantly (p is less than 0.05) smaller compared to experiment. Forecasted longer drought periods might reduce the growth of Scots pine in fertile forest types but silver birch growth might be affected in fertile mineral soils in future.

In the summer 2010, a study of the below-ground biomass of young (12 - and 14-year-old) Scots pine Pinus sylvestis L. stands was carried out in central Latvia. The fine-root (diameter is less than 2 mm) biomass, tips, length and volume were determined for the mineral soil layer (0 – 60 cm) by core sampling. The main objective was to determine the average fine-root biomass and morphological characteristics in different classes of young stands of Scots pines. The mean fine-root biomass was calculated for the whole stand by using below-ground biomass measurements of different components of sample trees and measurement of the tree stand. The amount of dry fine-root biomass in the soil layer was 5.3 ± 1.6 t haE-1 in the 14-year-old stand and 3.6 ± 1.5 t haE-1 in the 12-year-old stand. The study showed that the largest portion (52%) of the total fine-root biomass of 12 - and 14-year-old Scots pine stands was located at a depth of 0–10 cm, decreasing in deeper mineral soil layers. The average morphological characteristics of fine roots were higher in the older stand. Analysis of the morphology of fine roots showed that at soil depth of 0 – 10 cm the mean root length was 233 ± 44 cm, volume – 1.3 ± 0.6 cm3, value of tips – 537 ± 104 and diameter – 0.7 ± 0.1 mm per 100 cmE-3.

Leaf morphology was assessed in Pajiesys and Seirijai field trials of oaks. Oaks in these trials are the progenies of oak trees (Quercus genus) that grow in the Trakas forest of Seirijai district of Alytus forest enterprise of Lithuania. The aim of the study was to determine the number of hybrid trees between the progenies of the Trakas forest in Pajiesys and Seirijai field trials. 251 oaks belonging to 40 half-sib families were sampled. Twenty three leaf morphological variables were measured on each of 5 leaves collected from each tree and analysed by principal component analysis (PCA) and discriminant analysis (DA). The study concluded that Q. robur and Q. petraea leaves are most clearly identified by six morphological traits. Discriminant function of two traits for oak species separation was proposed. The study has also revealed a high degree of interspecific hybridization in field trials. Study results were compared with earlier reports about hybridization occurring in mixed oak stands in other parts of Europe.

Light is one of the most significant environmental factors affecting the growth of plants, as it is the driving force of photosynthesis. Among others, the red and blue light are the most relevant, as these spectral regions are absorbed by chlorophyll the most. In addition, red and blue light trigger specific photomorphogenic responses that allow plants to capture the available light efficiently. Accordingly, the proportion of red and blue light (R:B ratio) is considered one of the most important characteristics of light for plants, as optimal R:B provides balanced growth and photosynthesis. The aim of this study was to evaluate how the in vitro cultures of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) are affected by different R:B ratios under fixed illumination intensity. We examined the growth characteristics of plantlets under wide spectrum LED luminaires with three different R:B proportions – 1:1, 7:3 and 9:1. While photosynthesis-related variables were significantly affected by light, the effect on morphology was less pronounced. Overall, increased proportions of red light decreased the photosynthetic performance of plantlets without giving significant benefits in the form of longer shoots that could be used to facilitate propagation effectiveness. Nonetheless, the effect of light treatment remains at least partially clones-specific and should be considered in case of further application for propagation purposes.