Alejandra Vilela

Ecophysiology of Prosopis Species From the Arid Lands of Argentina: What Do We Know About Adaptation to Stressful Environments?

The expansion of the Prosopis genus from the sub-humid Chaco towards colder and drier zones such as Monte, Prepuna and Patagonia biogeographical regions would have implied the acquisition and/or adjustment of morphological and physiological adaptations to stressful environments. In this chapter, we discuss the phenological, morphological and physiological features of seven Prosopis species native to Argentinean arid regions that allow them to avoid or tolerate water stress, salinity, and other environmental stress factors in arid lands. Some of these adaptations appear to be spread over the genus and should confer the capability to deal with the most common stressful factor of arid lands (i.e. water availability); however, other morphological or physiological adaptations appear to be specific to each species, and should be the cause of niche differentiation among species and the occupation of particular environments within arid lands (e.g. sand dunes, saline environments). Finally, we discuss some consequences of these adaptations for the management of Prosopis species. The inter- and intra-specific variability observed in their adaptation to stressful factors suggest that some Prosopis species may be a good option to be used in the restoration of degraded areas or in afforestation projects with productive objectives.

Long-term effect of carbohydrate reserves on growth and reproduction of Prosopis denudans (Fabaceae): implications for conservation of woody perennials

We evaluated the usefulness of long-term plant carbon economy of a xerophyte shrub as a tool in conservation. Reserves manipulation through defoliation decreased reproduction in the long-term but not growth. Root and shoot reserves can be used as indicators of how much biomass can be harvested without threatening future reproduction

The impact of reproductive output on Prosopis denudans pod partition and chemical composition: Implications for economic utilization

The impact of reproductive output on Prosopis denudans pod partition and chemical composition: Implications for economic utilization.m Located in southern Argentina where the climate is dry, cold, and windy, the economy of the Patagonian shrub-steppes is based almost exclusively on sheep husbandry. In this ecosystem, grazing has been identified as one of the main causes of degradation, a process that hampers the sustainability of the region (1). A sustainable alternative that could increase the economic return in this area is to harvest native stands of target species capable of yielding raw industrial materials. One of the target species identified for the Chubut province (42 ~ S) is Prosopis denudans Bentham (2). Prosopis pods, which are rich in sugar, protein, and carbohydrates (3), are mostly consumed by wildlife and domestic herbivores (4). The importance of Prosopis pods for Indian cultures in North and South America has been very great in the past and is still considerable. The edible fruits are used as food in the form of meal or fermented beverages. The pod mesocarp, which is the spongy pulp between the pod exterior (exocarp) and the stony endocarp, is a source of flour and gum, both of which are suitable for human consumption (5). Because the taste and aroma of Prosopis flour is in the same general class as coffee/cacao/cinnamon/mocha, its greatest economic value will be achieved in flavoring/aroma applications of the food industry (5). The mesocarp of the fruits of Prosopis denudans also could be used as a source of gum (up to 10% of the fruits dry weight; 6). Because the development of Prosopis as a crop would be enhanced if the annual pod crop is efficiently utilized, much effort has been devoted to develop products suitable for use as a food ingredient (7, 8, 9). Despite the fact that the industrial technology to produce Prosopis flour seems to be ready, the great variation shown both in reproductive output and fruit quality does not allow for intensive utilization (10, 11) and, at the present time, flour is not used in any commercial application on a significant scale. In this regard, the proportion of the mesocarp of a fruit is a key factor for pod industrial utilization because it has a clear influence on the cost of the processes involved in the production of flours (5). See Figure 1. With this in mind, we tested the hypothesis that fruit size and partition (i.e., mesocarp proportion) are strongly influenced by the number of fruits produced by the plant in a given season. The objective of this work was to compare green and ripe pods partition into pericarp and seeds and their chemical composition in P. denudans individuals differing in reproductive output (highand low-pod yield individuals). Four morphological variables (fruit dry weight, pericarp:seed ratio, number of seeds, and seed dry weight) and two chemical variables (protein and total non-structural carbohydrate content) are described for four growth stages of Prosopis denudans pods. The results are discussed in the context of the economic utilization of the crop. Materials and methods: Three native populations of Prosopis denudans, located in the Patagonian province of Cbubut (Argentina), were selected for this study. In late spring (December), individuals bearing high quantities (HY) and low quantities (LY) of green pods were identified (10 reps/population). Two groups of plants with no significant differences in height (t test; P=0.47) and diameter (t test; P=0.23) were chosen for this study. Reproductive output as measured in grams (g) of mature fruits (12) and reproductive allocation [reproductive output (g)/aerial biomass produced during the last growing season in grams of dry weight (g D.W.; 13)] significantly differed (p<0.05) between HY (32.9 _+ 6.8 g fruit per plant and 0.053 -+ 0.007 g fruit [ g bi . . . . . ) and LY (5.8 -+ 0.8 g fruit per plant; 0.01 +0.003 g fruit [ g bi . . . . . ) individuals. Green pods were harvested and oven-dried at 50~ to constant weight. Growth stages were identified according to a pods width (stage 1 <_ 3 mm; stage 2 = 3.1-5 mm; stage 3 >_ 5.1 mm; and stage 4 (full size) = mature pod). Total non-structural carbohydrates (TNC) were determined by the anthrone method (14). Nitrogen determination was based

Tradeoffs between productivity and nitrogen conservation in wild and domesticated plants of the perennial crop Physaria (Brassicaceae): Tradeoffs between productivity and N conservation in perennial crops

Domestication of desert‐adapted perennials has been proposed as an alternative to increase cropping intensity in low input environments. However, selection for high yield in perennial crops provokes indirect changes in plant resource use. These changes might alter how nitrogen is acquired, allocated, used and stored, thus affecting plant longevity and yield stability. Using the perennial forb Physaria as a model, we compared the pattern of N allocation, use and conservation of high‐yield accessions (Y), and stable yield accessions (S), with their wild counterpart (W). We found a negative relationship between seed yield and N conservation capacity and their associated traits. The shift of strategy provoked by high yield selection implies changes in N allocation and a decrease in nitrogen use efficiency and conservation capacity at plant‐ and leaf‐level. S accessions also increase allocation to seeds, although they kept the N use and conservation traits of their wild counterparts, remaining in an intermediate position between the Y and W accessions profiles. The shift of strategy provoked by high yield selection implies a decrease in nitrogen use efficiency and conservation capacity that may be behind the loss of longevity and yield on subsequent years. Wild and stable accessions were more conservative and show traits that promote nitrogen conservation. These are key traits that should not be lost during the selection process if breeders want to achieve the adequate ideotype of perennial crop for arid systems.