Key words: m a i z e , d r o u g h t , w a t e r l o g g i n g , stress t o l e r a n c e , root m o r p h o l o g y , r o o t a n a t o m y Abstract Effects of soil drought or waterlogging on the morphological traits of the root system and internal root anatomy were studied in maize hybrids of different drought tolerance. The investigations comprised quantitative and qualitative am~lyses of a developed plant root system through determining the nnmber, length and dry matter of the particular components of the root system and some traits of the anatomical structure of the semihal root. Obtained results have demonstrated a relatively broad variation in the habit of the root system. This mainly refers, to the number, length and dry matter of lateral roots, developed by seminal root, seminal adventitious and nodal roots as well as to some anatomical properties of the stele, cortex and metaxylem elements.Plants grown under waterlogging or drought conditions showed a smaller number and less dry matter of lateral branching than plants grown in control conditions. The harmful effect of waterlogging conditions on the growth of roots was greater when compared with that of plants exposed to drought. In the measurements of the root morphological traits, the effect of soil drought on the internal root anatomical characteristic was weaker than the effect of soil waterlogging. The observed effects of both treatments were more distinct in a drought sensitive hybrid Pioneer D than in drought resistant Pioneer C one. The drought resistant hybrid Pioneer C distinguished by a more extensive rooting and by smaller alterations in the root roof phology caused by the stress conditions than drought sensitive hybrid Pioneer D one. Also the differences between the resistant and the sensitive maize hybrids were apparent for examined root anatomical traits. Results confirm that the hybrid Pioneer D of a high drought susceptibility was found to be also more sensitive to periodical soil water excess. A more efficient water use and a lower shoot to root (S:R) ratio were found to be major reasons lbr a higher stress resistance of the hybrid Pioneer C.The reasons/'or a different response of the examined hybrids to the conditions of drought or waterloggiug may be a more economical water balance and more favourable relations between the shoot and root dimensions in the drought resistanl geno--type. The observed modifications of the internal root structure caused by water deficit in plant tissues may partly influence on water conductivity and transport within roots.The results suggest that the morphological and anatomical traits of the maize root system may be used in practice as direct or indirect selection criteria in maize breeding.
Eighteen cultivars of legume species (field bean, soybean, field pea, lupine) were screened for drought tolerance in 3 year‐long field experiments. The aim of the investigations was to evaluate the generic variation of drought susceptibility of the tested varieties. The experimental plots were equipped with an installation which enabled the limitation of the water content in soil and soil irrigation. The applied drought susceptibility index (DSI) considered the relations between seed yield of plants under drought conditions (YD) and that under conditions of good soil watering (YIR) as well as their dependence on the drought severity index (DS). The use of the index divided the cultivars into two groups of different drought tolerances. The group of drought resistant cultivars characterized by mean values of the DSI index < 0.31 comprised field bean cultivars Bourdon, Gobo and Nadwislanski, soybean cultivars Aldana, Polan and Progres, field pea cultivars Miko and Solara and lupine cultivars Popiel and Bac. To the drought sensitive cultivars with DSI > 0.44 belonged Victor and Bronto of field bean species, Bareness and Mige of field pea species and Emir of lupine species. In general, the resistant cultivars when compared with the susceptible ones were characterized by lesser yield of seeds, which, however, was more stable both under conditions of drought and moistured plots. Any dependence of the degree of drought tolerance on the duration of the particular periods of plant growth was not observed in the experiments, however, both in’ drought susceptible and drought resistant cultivars there appeared the tendency to shorten the development phases under drought and to prolong them under artificial irrigation. In general, based on the results obtained, it can be concluded that legume plants belong to the species sensitive to water supply. The observed decrease of plant seed yield under moderate natural soil dryness in the year 1993 differed only a little from that found in experiments in the years 1994 and 1995, when soil dryness was much more severe.
The conditions were investigated under which the development cycle in winter rape could be markedly reduced by grafting. Scions from non vernalized seedlings were grafted onto stock plants beginning their generative phase. Winter rape plants vernalized under natural field conditions and spring rape plants in the initial generative phase were used as stock. Best results were obtained by grafting scions from plants at the stage of 4 leaves, i.e. after 3 weeks of growth, onto winter rape stock. With such scions the effectiveness of graftings was high and seed crops were obtained 170 days earlier than under natural field conditions of growth and 80 days earlier than under artificial conditions. Scions grafted onto winter rape stock produced more siliques than those on spring rape. Grafting of scions after cutting off their apical meristems allowed formation of side shoots and consequently resulted in higher yields of siliques; the formation of siliques, however, was delayed by about 10 days as compared to grafts with apical meristems
The uptake rale of ~4Cqabelled sucrose, myo-inositol and PC was studied in callus cultures of two oilseed rape cultivars, characterized by different in vitro regeneration ability. Transfer of calli onto regeneration stimulating medium resulted in changes of examined substances uptake rate, which were depended on tissue morphogenic potential. Non-regenerating calli of both cultivars increased uptake rate of sucrose whereas changes in incorporation of other compounds were under gehome control. Significant increase of uptake rate of all tested compounds was observed as result of organogenesis initiation. Such differences, in the responses of organogenic and non-organogenic tissue indicate that this parameter could be useful as marker of organogenesis A correlation was observed between the rate of sucrose uptake and its concentration in the medium, which suggests an advan-1age to passive transport through the callus cell membrane. Lack of such correlation in the case of other labels indicates that this processes are selective and under cell control.
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