LEAF WATER STATUS AND PHOTOSYNTHETIC GAS EXCHANGE OF PISTACIA KHINJUK AND P. MUTICA EXPOSED TO OSMOTIC DROUGHT STRESS

Predawn leaf water potential (psipd) and morning values of leaf gas exchange, as net photosynthesis (A), stomatal conductance (gs), transpiration (E), and morning leaf water potential (psimn) were determined seasonally in 22 woody cerrado species growing under natural conditions. Despite the lower mean values of psipd in the dry season (-0.35 ± 0.23 MPa) compared to the wet season (-0.08 ± 0.03 MPa), the lowest psipd in the dry season (-0.90 ± 0.00 MPa) still showed a good nocturnal leaf water status recovery for all species studied through out the year. Mean gs values dropped 78 % in the dry season, when the vapor pressure of the air was 80% greater than in the wet season. This reduction in gs led to an average reduction of 33% in both A and E, enabling the maintainance of water use efficiency (WUE) during the dry season. Network connectance analysis detected a change in the relationship between leaf gas exchange and psimn in the dry season, mainly between gs-E and E-WUE. A slight global connectance value increase (7.25 %) suggested there was no severe water stress during the dry season. Multivariate analysis showed no link between seasonal response and species deciduousness, suggesting similar behavior in remaining leaves for most of the studied species concerning leaf gas exchange and psimn under natural drought.

Download Full-text

Yellow lupin (Lupinus luteus) tolerates waterlogging better than narrow-leafed lupin (L. angustifolius) II. Leaf gas exchange, plant water status, and nitrogen accumulation

Australian Journal of Agricultural Research ◽

10.1071/ar99074 ◽

2000 ◽

Vol 51 (6) ◽

pp. 711 ◽

Cited By ~ 8

Author(s):

C. L. Davies ◽

D. W. Turner ◽

M. Dracup

Keyword(s):

Gas Exchange ◽

Leaf Gas Exchange ◽

Water Status ◽

Recovery Period ◽

Leaf Water ◽

Lupinus Luteus ◽

Nitrogen Accumulation ◽

Growth Responses ◽

Yellow Lupin ◽

Leaf Water Status

Yellow lupin (Lupinus luteus) may have potential as a legume crop in waterlogging-prone areas of Western Australia. To elucidate the physiological response of yellow lupin and the widely grown narrow-leafed lupin (L. angustifolius) to transient waterlogging we conducted experiments in controlled environments. Narrow-leafed lupin and yellow lupin were grown in pots and waterlogged for 14 days from 28 to 42, or 56 to 70 days after sowing, each being followed by a 14-day recovery period. Root and shoot growth responses, leaf gas exchange, water relations, and N accumulation were assessed. During the period of waterlogging, net nitrogen accumulation ceased in both species at both ages. During recovery, yellow lupin accumulated more nitrogen than narrow-leafed lupin. Waterlogging reduced leaf gas exchange more with older plants than with younger plants, and more so with narrow-leafed lupin than yellow lupin. Some components of leaf gas exchange, particularly leaf conductance, were reduced by up to 80%. Waterlogging had no effect on leaf water potential of yellow lupin but reduced it in narrow-leafed lupin, from about –450 to –1100 kPa, especially during the recovery period. Yellow lupin was more adapted to transient waterlogging than narrow-leafed lupin because it maintained its leaf water status, it accumulated more nitrogen during recovery, and its photosynthetic activity recovered quickly afterremoval of waterlogging.

Download Full-text

DROUGHT RESISTANCE OF Sorghum bicolor. 4. HORMAL CHANGES IN RELATION TO DROUGHT STRESS IN FIELD-GROWN PLANTS

Canadian Journal of Plant Science ◽

10.4141/cjps82-050 ◽

1982 ◽

Vol 62 (2) ◽

pp. 317-330 ◽

Cited By ~ 7

Author(s):

T. KANNANGARA ◽

R. C. DURLEY ◽

G. M. SIMPSON ◽

D. G. STOUT

Keyword(s):

Drought Stress ◽

Sorghum Bicolor ◽

Water Potential ◽

Leaf Water Potential ◽

Leaf Senescence ◽

Water Status ◽

Leaf Water ◽

Vegetative Stage ◽

Leaf Water Status ◽

Drought Tolerant

This study was undertaken to investigate the nature of hormonal changes in relation to drought stress in two cultivars of Sorghum bicolor L. Moench. Two cultivars, M–35 and NK300, were grown in a field plot protected by a rain shelter. Plants in one soil compartment were stressed by withholding water while those in another (controls) were irrigated frequently. Levels of the plant hormones abscisic acid (ABA), phaseic acid (PA) and indole-3-acetic acid (IAA) measured by high-performance liquid chromatography (HPLC) were determined in the youngest leaves of control and stressed plants at intervals throughout the growth cycle. Plant height, senescence, and leaf water status were also determined. Leaf water potential (ψw) and solute potential (ψs) were reduced in both cultivars by drought stress; values for M–35 plants were lower than NK300. Leaf senescence was higher in M–35 plants and was promoted by stress in both cultivars. Cultivar M–35 behaved as a drought-tolerant plant whereas cultivar NK300 behaved more like a drought avoider. ABA levels were higher in M–35 control plants than in corresponding NK300 plants and levels in both cultivars followed seasonal changes in leaf water potential. Under drought stress, ABA levels increased between 1.5 and 2 times in both cultivars with the largest increases occurring during the vegetative stage in M–35 and during the flowering stage for NK300. PA levels in both cultivars were higher in stressed than in control plants. PA levels in M–35 plants were relatively low and constant throughout the life cycle, whereas in NK300, levels were high until shortly before flowering. IAA levels were higher in NK300 than in M–35 plants, particularly during the vegetative stage. Under drought stress, IAA levels were reduced in both cultivars with a more pronounced reduction in NK300. The high level of ABA in the more drought-tolerant cultivar M–35 was associated with low leaf ψw and ψs and high leaf senescence. On the other hand, in the drought avoider, NK300, high levels of IAA and PA were associated with high leaf ψw and ψs. It is concluded that these cultivars, which differ in their response to drought stress, can be distinguished by their leaf hormone levels.

Download Full-text