Biomass Partitioning and Gas Exchange in Dalbergia sissoo seedlings under water stress

Abstract

Biomass, leaf water potential (Ψ l ), net photosynthetic rate (P N ), transpiration rate (E), stomatal conductance (g s ), leaf to air temperature difference (T diff ), and instantaneous water use efficiency (WUE) were measured in the seedlings of Dalbergia sissoo Roxb. grown under irrigation of 20 (W 1 ), 14 (W 2 ), 10 (W 3 ), and 8 (W 4 ) mm. Treatments were maintained by re-irrigation when water content of the soil reached 7.4 % in W 1 , 5.6 % in W 2 , 4.3 % in W 3 , and 3.2 % in W 4 . Seedlings in a control (W 5 ) were left without irrigation after maintaining the soil field capacity (10.7 %). Seedlings of W 1 had highest biomass that was one tenth in W 5 . Biomass allocation was highest in leaf in W 2 and in root in W 4 and W 5 treatments. Difference between predawn leaf water potential (Ψ Pd ) and midday (Ψ mid ) increased with soil water stress and with vapour pressure deficit (VPD) in April and May slowing down the recovery in plant leaf water status after transpiration loss. P N , E, and g s declined and T diff increased from W 1 to W 5 . Their values were highly significant in April and May for the severely stressed seedlings of W 4 and W 5 . P N increased from 08:00 to 10:00 and E increased until 13:00 within the day for most of the seedlings whereas g s decreased throughout the day from 08:00 to 17:00. P N and E were highest in March but their values were low in January, February, April, and May. Large variations in physiological variables to air temperature, photosynthetically active radiation, and vapour pressure deficit (VPD) indicated greater sensitivity of the species to environmental factors. WUE increased from W 1 to W 2 but decreased drastically at high water stress particularly during hot summer showing a kind of adaptation in D. sissoo to water stress. However, low biomass and reduced physiological functions at <50 % of soil field capacity suggest that this species does not produce significant biomass at severe soil water stress or drought of a prolonged period.

Responses of dominant desert species Artemisia ordosica and Salix psammophila to water stress

“…Decrease in biomass in response to water stress is a commonly observed phenomenon (Guenni et al 2002, Singh andSingh 2003). For the two tested species, tree height, number of leaves, and leaf area were also decreased by water limitation.…”

Effects of water stress on growth, dry matter allocation and water-use efficiency of a leguminous species, Sophora davidii

“…The lower WUE under drought might be due to a greater effect on biomass production than on water-use. Under severe drought, a lower conductance of CO 2 and activity of photosynthetic enzymes in leaves of Dalbergia sissoo decreased photosynthesis and biomass, which reduced WUE (Singh and Singh 2003).…”

Effects of drought stress and N supply on the growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings

“…Similar conclusion also can be drawn from analyzing the responses of RWC. The efficiency indicator reflects the capacity of plants recovering to a favorable water status and their drought tolerance (Singh and Singh, 2003;Rosales-Serna et al, 2004). Although drought stress slightly decreased RWC as many previous studies have reported (Chartzoulakis et al, 2002;Rosales-Serna et al, 2004;Bai et al, 2006), Nl also increased RWC under a drought stress condition, and RWC increased with the increase of N supply under well-watered condition.…”