**5. Water deficit on nitrogen compounds**

Lobato et al. [50] evaluated the effects of the progressive water deficit, as well as investigated the physiological and biochemical behavior in *G. max* cv. Sambaiba that was submitted to water restriction during the vegetative phase (Table 1). The increase in the levels of free amino acids is due to high synthesis of amino acids from protein hydrolyses, in which case the free amino acids are utilized by the plant to reduce the effects of the water deficit through organic solute accumulation, thereby increasing the water retention capacity [51].

Under water stress, the free amino acids such as proline and glycinebetaine are strongly influenced and consequently quickly accumulated [52], as well as of secondary form occur the increase of aspartate, glutamate and alanine [53]. The result on increase in the free amino acids found by Asha and Rao [54] while working with *Arachis hypogaea* under water deficit corrob‐ orates the results of this study.


The reduction in relative water content in leaf is because of lower absorption rate of water by plant via roots and water loss occasioned by gas exchanges through stomata [43]. Similar

Water deficit promoted a significant fall in stomatal conductance of the two cultivars, but tolerant plants presented higher values of this variable, probably by maintaining better plant water condition. This study revealed that root dry matter exercises influence on stomatal conductance in *V. unguiculata* plants submitted to 5 days of water deficiency, and this fact is based on the indirect effect produced by root on stomatal mechanisms. In other words, an insufficient root system developed during water deficiency will supply lower amount of water

Decrease in stomatal conductance is explained by reduction in water availability in substrate, and it produces a reduction in leaf water potential, with consequent stomatal closing. The results described by Santos and Carlesso [4] reported that on conditions of water deficit, there

Gholz et al. [45] reported that stomatal closing reduces the CO2 influx to leaf, affecting production, transport, and utilization of photo-assimilates, and hence the yield. Results similar to those found in this study were found by Santos et al. [46], who studied five *P. vulgaris*

Decrease in transpiration rate of *V. unguiculata* plants can be attributed to stomatal behavior, because under water deficit, stomata are kept partially closed, contributing to change in transpiration behavior of plant [47]. Leite and Filho [48] reported that reduction of transpira‐ tion is an important mechanism of tolerance to drought. Values of transpiration demonstrated direct relation with stomatal conductance and also with leaf relative water content. Similar results were shown by Nogueira et al. [49] in a study oftwo *Arachis hypogeae* cultivars exposed

Lobato et al. [50] evaluated the effects of the progressive water deficit, as well as investigated the physiological and biochemical behavior in *G. max* cv. Sambaiba that was submitted to water restriction during the vegetative phase (Table 1). The increase in the levels of free amino acids is due to high synthesis of amino acids from protein hydrolyses, in which case the free amino acids are utilized by the plant to reduce the effects of the water deficit through organic solute

Under water stress, the free amino acids such as proline and glycinebetaine are strongly influenced and consequently quickly accumulated [52], as well as of secondary form occur the increase of aspartate, glutamate and alanine [53]. The result on increase in the free amino acids found by Asha and Rao [54] while working with *Arachis hypogaea* under water deficit corrob‐

results were reported by Maia et al. [44] when working with *Zea mays*.

284 Abiotic and Biotic Stress in Plants - Recent Advances and Future Perspectives

to shoot and, consequently, will promote reduction in stomatal conductance.

is an increase in ABA concentration in xylem sap, promoting stomata closing.

genotypes subjected to water deficiency.

**5. Water deficit on nitrogen compounds**

accumulation, thereby increasing the water retention capacity [51].

to water deficiency.

orates the results of this study.

**Table 1.** Free amino acids and proline in *Glycine max* plants (cv. Sambaiba) under 0, 2, 4, and 6 days of water deficit. Averages followed by the same letter do not differ among themselves by Tukey's test at 5% of probability [50].

The reduction in the total soluble proteins showed in the plants under water stress is due to probable increase in the proteases enzyme activity (Table 2), in which case this proteolytic enzyme promotes the breakdown of the proteins and, consequently, decreases the protein amount presents in the plant under abiotic stress conditions [55]. In inadequate conditions to the plant is active the pathway of proteins breakdown, because the plant use the proteins to the synthesis of nitrogen compounds as amino acids that might auxiliary the plant osmotic adjustment [56]. Similar results on reduction in the proteins were found by Ramos et al. [57], investigating the effects of the water stress in *P. vulgaris*.


**Table 2.** Total soluble proteins in *Glycine max* plants (cv. Sambaiba) under 0, 2, 4, and 6 days of water deficit. Averages followed by the same letter do not differ among themselves by Tukey's test at 5% of probability [50].
