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Accumulation of various osmolytes was examined in plants of sugar beet cv. Janus grown under two soil water treatments: control (60% of the field water capacity; FWC) and drought (30-35% FWC). The water shortage started on the 61st day after emergence (DAE), at the stage of the beginning of tap-roots development and was imposed for 35 days. Osmotic potential of sugar beet plant organs, particularly tap-roots, was decreased significantly as a consequence of a long-term drought. Water shortage reduced univalent (K + , Na + ) cations concentrations in the petioles and divalent (Ca 2+ , Mg 2+ ) ions level in the mature and old leaves. Cation concentrations in the taproots were not affected by water shortage. The ratio of univalent to divalent cations was significantly increased in young leaves and petioles as a consequence of drought. Long-term water deficit caused a significant reduction of inorganic phosphorus (P i ) concentration in young and old leaves. Under the water stress condition, the concentration of proline was increased in all individual plant organs, except proline concentration in the youngest leaves. Drought treatment caused a significant increase of glycine betaine content in shoot without any change in tap-roots. Glucose concentrations were significantly increased only in tap-roots as the effect of drought. In response to water shortage the accumulation of sucrose was observed in all the examined leaves and tap-roots. Overall, a long-term drought activated an effective mechanism for osmotic adjustment both in the shoot and in the root tissues which may be critical to survival rather than to maintain plant growth but sugar beet organs accumulate different solutes as a response to water cessation.

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Growth response of sugar beet plants to drought stress applied at different growth stages has been investigated. Cessation of watering imposed moderate water stress and resulted in the reduction of the relative water content of young and old leaves maximally by 6%. However, water content in taproot was more drastically decreased than in the shoot. Water withholding reduced dry ma�er accumulation and leaf assimilatory expansion when imposed at successive growth stages, especially in the case of earlier stress application. Substantial change in distribution pa�ern was observed when stress affected foliar development, more than 80% of dry ma�er was accumulated in the taproots. Water shortage negatively influenced both taproot and sugar yield by 16-52%, depending on the stress timing in the season. Drought stress did not change the sucrose concentration but when occurred in foliar and early stage of root development, decreased the contents of important non-sugar compounds like potassium and α-amino-N solutes in the final yield. Overall, data concerning the different water status in particular organs implies that a hydrodynamic equilibrium does not exist within the sugar beet plant as a response to water stress. Drought imposed on the earlier stage, most drastically influenced plant growth and final yield. When water stress occurs at the end of crop cycle, sugar beet plants had a higher ability to recovery their growth.Keywords: Beta vulgaris L.; drought; dry ma�er partitioning; growth; leaf area; water content; yield quantity and quality Supported in the frames of KBN Grant 5 PO6A 028 18.

The aim of this work was to determine two types of photosynthetic water-use efficiency in order to examine their utility as selection criteria for tolerance of energy crops to soil water deficit. Furthermore, effects of crop cultivation on soil water content and storage were investigated. Seven energy crops were examined: miscanthus, prairie cordgrass, willow, thornfree rose, Virginia mallow, Bohemian knotweed, and topinambour. The highest values of instantaneous (WUE) and intrinsic (WUE i ) water-use efficiencies were found for miscanthus and prairie cordgrass. The reduction of WUE and/or WUE i was caused mainly by a rapid rise in the transpiration rate and a greater stomatal conductance, respectively. Principal component analysis showed that neither WUE nor WUE i could be recommended as universal selection criteria for the drought tolerance in different energy crops. The proper localization of soil with a good supply of water is most the important condition for energy crop plantations.

Alterations in some physiological processes in source leaves of sugar beet-such as chlorophyll and carbohydrate concentrations, stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants were infected at different times of their growth period: on the sowing day and 4 or 8 weeks after sowing. A variation treatment, with nonpelleted seeds infected on the sowing day, was also analyzed. The experiment showed that development of disease symptoms depends on the time of infection and seed protection. A significant root yield decrease was observed in case of late infection, as compared to the yield of plants infected on the sowing day. The fresh weight of leaves was significantly increased where there was late infection. The infected plants showed a lower content of K + , Na + and α-amino-N than did the controls. Infection by A. cochlioides induced chlorophyll degradation mostly in older leaves with the occurrence of natural senescence processes. Chlorophyll fluorescence parameters indicated that the photosynthetic apparatus of younger leaves was more sensitive to pathogen infection, when compared to older ones. The photochemical efficiency of photosystem II was reduced in young leaves mainly due to disturbance of the water-splitting system. In plants grown from non-pelleted seeds a strong impairment of PSII was observed only in those leaves which developed during early pathogen infection. In young leaves of plants infected in the fourth week after sowing, inhibition of the rate of net photosynthesis was correlated with the increase in intercellular CO 2 concentration, indicating some disturbance in the carbon assimilation phase. In mature leaves of late infected plants the reduction of photosynthesis net rate was associated with a decrease of stomatal conductance and an increase of diffusion resistance to CO 2 and H 2 O, which was also the cause of the transpiration rate inhibition. When the leaves developed during early infection, an increase of specific leaf weight and accumulation of carbohydrates was observed. In mature leaves of nonprotected plants infected on the sowing day, the recovery of all physiological processes was observed together with a diminution of disease symptoms.

This paper is a continuation of our studies related to the response of two tomato cultivars: Robin and New Yorker to chilling; the later is more tolerant to chilling than the former one (Starck et aL 1994). The concentration of ABA in the xylem sap and ABA delivery rate (calculated as the amount of ABA exuded in 2h from the cut stump, following shoot removal) were estimated by ELISA. The relative water content (RWC) of the leaf blades and stomatal resistance (RS) were also measured. Tomato plants were grown in a greenhouse, under noncontrolled conditions. Before chilling some of the plants were drought hardened tbr 10 days (H). As an consequence of water deficit only New Yorker growth slightly decreased. Plants were chilled to 2-5 °C during three consecutive, 16-h nights, preceded by warm days, which caused a decrease in the RWC of leaf blades. Chilling did not decreased leaf blade hydration significantly, but drastically increased the concentration of ABA in the xylem sap in more chilling tolerant cv. New Yorker only. The delivery rate of ABA was markedly enhanced in both cultivars, but much more in New Yorker. Drought hardening increased ABA delivery rate in cv.Robin only, especially after chilling. The lack of correlation between changes in the RWC of leaf blades after low temperature treatment and the concentration of AB A in the xylem sap as well as its delivery rate suggest, that in both tomato cultivars chilling increased ABA level directly, not as an secondery effect of temperature-induced water deficit.