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PubMed2006

Mitigation of effects of extreme drought during stage III of peach fruit development by summer pruning and fruit thinning.

A water deficit during stage III of fruit growth was established with the aim of determining if it is possible to achieve an improvement in tree water status by summer pruning and fruit thinning. The experiment was set up as a randomized block split-plot design across trials (irrigation) where pruning was assigned to the main plot and fruit thinning to the sub-plots. The irrigation treatments were (1) standard full irrigation (FI), and (2) suppression of irrigation during stage III of fruit growth until leaves visibly withered (LWI); the pruning treatments were (1) experimental summer pruning (EP), and (2) standard summer pruning (CP); and three fruit thinning intensities were applied to facilitate analysis of the effects of the treatments in relation to fruit load. Changes in amount of light intercepted and in tree stem water potential (Psi stem) were evaluated. The EP treatment reduced the amount of light intercepted by the tree. In the FI treatment, there was a significant reduction in fruit growth measured as both water accumulation and dry mass accumulation. Under FI conditions, reductions in fruit load as a result of EP were not accompanied by a significant improvement in Psi stem. In the LWI treatment, EP produced a significant improvement of 0.17 MPa in Psi stem, but there was no improvement in fruit growth compared with CP trees. A reduction in fruit load from 350 (commercial load) to 150 per tree significantly improved Psi stem by 0.3 MPa at the end of stage III of fruit growth. These results indicate that improvements in water status in response to pruning may be insufficient to promote fruit growth if the pruned trees are unable to provide an adequate supply of assimilates to the developing fruits.

Disasters↗
PubMed1989

Selection for salt and drought tolerance in protoplast- and explant-derived tissue cultures of Colt cherry (Prunus avium x pseudocerasus).

Colt cherry (Prunus avium x pseudocerasus) callus cultures were derived from leaf protoplasts, protoplasts of root cell suspension cultures, or by direct culture of leaf and root tissues. Survival of calli cultured on basal proliferation medium containing 25, 50, 100 or 200 mN (millinormal) NaCl, Na(2)SO(4) or KCl, or iso-osmotic (with NaCl) concentrations of mannitol ranged from 1 to 15%. After six transfers on the same medium, surviving cell lines were subjected to three cycles of direct recurrent selection; i.e., in each cycle, they were cultured alternately on basal proliferation medium, and on basal proliferation medium supplemented with NaCl, KCl, Na(2)SO(4) or mannitol. Salt- or mannitol-tolerant cell lines selected in this way had smaller cells than unselected cell lines, and they grew more rapidly and had higher callus and cell survival rates than unselected cell lines when cultured in the presence of salt or mannitol. Cells lines selected for tolerance to one agent (sodium salt, potassium salt or mannitol) showed minimal tolerance to another agent. However, when plants were regenerated from salt- or mannitol-tolerant callus and new cultures derived from them, the new cultures showed tolerance to all of the salts and mannitol. Plant regeneration from the new cultures was not achieved under the conditions that led to the regeneration of the parent plants from callus.

Journal Article↗
PubMed2003

Water for food and nature in drought-prone tropics: vapour shift in rain-fed agriculture.

This paper quantifies the eco-hydrological challenge up until 2050 of producing food in balance with goods and services generated by water-dependent ecosystems in nature. Particular focus is given to the savannah zone, covering 40% of the land area in the world, where water scarcity constitutes a serious constraint to sustainable development. The analysis indicates an urgent need for a new green revolution, which focuses on upgrading rain-fed agriculture. Water requirements to produce adequate diets for humans are shown to be relatively generic irrespective of hydro-climate, amounting to a global average of 1,300 m(3) cap(-1) yr(-1). Present food production requires an estimated 6,800 km(3) yr(-1) of consumptive green water (5,000 km(3) yr(-1) in rain-fed agriculture and 1,800 km(3) yr(-1) from irrigated crops). Without considering water productivity gains, an additional 5,800 km(3) yr(-1) of water is needed to feed a growing population in 2,050 and eradicate malnutrition. It is shown that the bulk of this water will be used in rain-fed agriculture. A dynamic analysis of water productivity and management options indicates that large 'crop per drop' improvements can be achieved at the farm level. Vapour shift in favour of productive green water flow as crop transpiration could result in relative water savings of 500 km(3) yr(-1) in semi-arid rain-fed agriculture.

Agriculture↗
PubMed1996

Drought-Induced Xylem Dysfunction in Petioles, Branches, and Roots of Populus balsamifera L. and Alnus glutinosa (L.) Gaertn.

Variation in vulnerability to xylem cavitation was measured within individual organs of Populus balsamifera L. and Alnus glutinosa (L.) Gaertn. Cavitation was quantified by three different techniques: (a) measuring acoustic emissions, (b) measuring loss of hydraulic conductance while air-dehydrating a branch, and (c) measuring loss of hydraulic conductance as a function of positive air pressure injected into the xylem. All of these techniques gave similar results. In Populus, petioles were more resistant than branches, and branches were more resistant than roots. This corresponded to the pattern of vessel width: maximum vessel diameter in 1- to 2-year-old roots was 140 [mu]m, compared to 65 and 45 [mu]m in rapidly growing 1-year-old shoots and petioles, respectively. Cavitation in Populus petioles started at a threshold water potential of -1.1 MPa. The lowest leaf water potential observed was -0.9 MPa. In Alnus, there was no relationship between vessel diameter and the cavitation response of a plant organ. Although conduits were narrower in petioles than in branches, petioles were more vulnerable to cavitation. Cavitation in petioles was detected when water potential fell below -1.2 MPa. This value equaled midday leaf water potential in late June. As in Populus, roots were the most vulnerable organ. The significance of different cavitation thresholds in individual plant organs is discussed.

Journal Article↗