Jasenka Antunović

Endogenous Auxin Profile in the Christmas Rose (Helleborus niger L.) Flower and Fruit: Free and Amide Conjugated IAA

The reproductive development of the Christmas rose (Helleborus niger L.) is characterized by an uncommon feature in the world of flowering plants: after fertilization the white perianth becomes green and photosynthetically active and persists during fruit development. In the flowers in which fertilization was prevented by emasculation (unfertilized) or entire reproductive organs were removed (depistillated), the elongation of the peduncle was reduced by 20–30%, and vascular development, particularly lignin deposition in sclerenchyma, was arrested. Chlorophyll accumulation in sepals and their photosynthetic efficacy were up to 80% lower in comparison to fertilized flowers. Endogenous auxins were investigated in floral and fruit tissues and their potential roles in these processes are discussed. Analytical data of free indole-3-acetic acid, indole-3-ethanol (IEt), and seven amino acid conjugates were afforded by LC-MS/MS in floral tissues of fertilized as well as unfertilized and depistillated flowers. Among amino acid conjugates, novel ones with Val, Gly, and Phe were identified and quantified in the anthers, and in the fruit during development. Reproductive organs before fertilization followed by developing fruit at post-anthesis were the main source of auxin. Tissues of unfertilized and depistillated flowers accumulated significantly lower levels of auxin. Upon depistillation, auxin content in the peduncle and sepal was decreased to 4 and 45%, respectively, in comparison to fruit-bearing flowers. This study suggests that auxin arising in developing fruit may participate, in part, in the coordination of the Christmas rose peduncle elongation and its vascular development.

Photosynthetic performance index in early stage of growth, water use efficiency, and grain yield of winter barley cultivars

Repetitive heat and drought stress conditions have a significant impact on quantity and quality of barley (Hordeum vulgare L.) production in most regions of the world. Objective of this study was to determine the relationships between photosynthetic performance index (PIABS), water use (WU), grain yield-based water use efficiency (WUEG), and grain yield per pot (GYP) of winter barley cultivars grown in a pot trial under short-term drought stress conditions and grain yield and its stability from the multi-environmental field trials. Ten winter barley cultivars were examined in two water treatments. One treatment was well watered, while the second treatment was subjected to short-term stress caused by deficiency of water in the stages of full tillering, beginning of heading, and grain filling. PIABS was measured at full tillering stage while WU, WUEG, and GYP of barley cultivars were estimated after the whole vegetative cycle. Also, multi-environmental field trials with the same winter barley cultivars were carried out during 4 yr (2004- 2007) and 3 yr (2009-2011) with two sowing densities (300 and 450 seeds m-2) on multiple locations in the lowland part of the Republic of Croatia. ANOVA showed highly significant (P ≤ 0.001) cultivar effect for all of the examined traits in the pot trial. PIABS of cultivars in both treatments was in a negative nonsignificant correlation with grain yield and grain yield stability (ecovalence) of the same cultivars in multi-environmental field trials. Winter barley cultivars with higher WU and WUEG also had higher values of grain yield, and harvest index observed on the basis of the pot trial. WU, WUEG, and GYP of 10 barley cultivars in pot trial showed highly positive phenotypic correlation with grain yield of all eight and 10 barley cultivars in the multi-environmental field trials. These results suggests that WU and WUEG could be good indicators for preliminary selection of modern, high yielding, and stable winter barley genotypes which have better water management capabilities.