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The effect of water stress on photosynthesis of spring barley

100%

Hejnak V., Krizkova J.

Zeszyty Problemowe Postępów Nauk Rolniczych

2004

tom 496

nr 1

The effect of water stress on gas exchange and photosynthesis of spring barley (Hordeum vulgare L, conv. distichon) was measured in small-plot trials in leaves of two modern malting varieties - Amulet and Krona - and historical cv. Nürnberg cultivated on medium-heavy fluvisol in the years 2000 - 2002. The diagram of the experiment included two variants of moisture conditions in small plots for each variety - soil moisture during the whole vegetation on the level 60-70% of maximum water capacity (MWC); and drought - soil moisture at the level of 30-35% of MWC induced in half of plots in the period from 25.DC to 61.DC. The parameters of gas exchange - net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (gs), and stomatal resistance (rs) - were measured by gas exchange system LCA-4 (ADC Bio Scientific) on photosynthetically active leaves during ontogeny of spring barley: 1st measurement - start of tillering phase (21.DC); 2nd measurement - start of shooting (phase 31.DC); 3rd measurement - start of flowering phase (61.DC); 4,h measurement - milk ripeness phase (75.DC); 5,th measurement - wax ripeness phase (85.DC). DC is decimal code for growth stages of spring barley after Zadoks et al. [1974]. The photosynthesis rate (Pn), transpiration rate (E) and stomatal conductance (gs) in leaves of spring barley plants had a dynamic character and very similar progress during ontogeny of this spring barley varieties. The values of gas exchange parameters accrued generally in the first part of their ontogeny and they reached maximum at the start of flowering phase. The natural ageing of the assimilation apparatus in the post-floral period manifested a significant decrease in values of stomatal conductance and photosynthesis rate. On the other hand, the value of stomatal resistance increased in the post-floral period. Water stress (soil drought) was a statistically significant limiting factor of photosynthetic activity of the assimilation apparatus and decreased the parameters of gas exchange (gs, Pn and E) in all three spring barley studied varieties. The significant decline of stomatal conductance was measured in leaves of spring barley plants stressed by drought as compared with plants growing on the favourable moisture conditions at the start of flowering phase. This decrease was from 0.26 mmol H2O.m-2.s-1 to 0.11 mmol H20.m-2.s-1 in Amulet variety, from 0.27 to 0.08 mmol H2O.m-2.s-1 in Krona variety, and from 0.28 to 0.12 mmol H2O.m-2.s-1 in Nürnberg variety. The stomatal closure manifested itself in the significant stoma- tal limitation of photosynthesis at the start of the (lowering phase. The average rate of photosynthesis reached in the stressed plants of Amulet variety was 58%, in the stressed plants of Krona variety it was 61% and in the stressed plants of Nürnberg variety it was 43% of the average level of photosynthetic rate of plants non-stressed by drought. Photosynthetic activity of the assimilation apparatus escalated after the end of water stress mostly in Amulet variety (measured in phase 75.DC). However, photosynthetic rate did not achieve the level of non- stressed plants.

The effect of water stress on photosynthesis of spring barley

100%

Krizkova J., Hejnak V.

Acta Physiologiae Plantarum

2003

tom 25

nr 3 suppl.

Ograniczanie wyników

1 Acta Physiologiae Plantarum

1 Zeszyty Problemowe Postępów Nauk Rolniczych

2 Hejnak V.

2 Krizkova J.

1 2004

1 2003

Wyniki wyszukiwania

The effect of water stress on photosynthesis of spring barley

The effect of water stress on photosynthesis of spring barley