The purpose of this paper is to propose an attempt to classify plural forms, based on the rationality underlying the choice of a portfolio of governance structures. Everything else constant, the firm would choose the least costly means of conducting transactions. The choice between making and buying would be based on the comparative efficiency of the market and the hierarchy to perform the same operations. The classification presented here does not pretend to be exhaustive, admitting the possibility of new studies revealing categories not yet identified in the literature. Root distribution and root system architecture are more affected by soil type and training system than by rootstock genotype Smart et al.
In several species including the overall, roughly isohydric grapevine Prieto et al. In addition, drought effect on root hydraulic conductivity may differ between rootstocks.
Although the result is similar — the use of different structures to govern the same transaction — the motives that lead to the choice may be diverse, and they are relevant to the understanding of the phenomenon. Physiological responses to water deficit Drop in plant water potential as a primary consequence of water deficit Water potential characterizes water availability from a thermodynamic point of view. When the gains from cooperation are limited to one stage of the production process and the contribution of each agent is well defined as in the joint acquisition of inputs by a pool of independent producers , short-term contracts would prevail.
Limitation of transpiration releases hydraulic tension and saves water One of the most obvious and immediate effects of water deficit is a reduction in shoot growth Chaves, , with cell expansion being particularly sensitive to water shortage Hsiao, Rootstocks: the hidden half While the choice of scion varieties is often regulated by their performance in specific climatic conditions or marketing purposes van Leeuwen and Seguin, , rootstocks offer more flexible solutions for adapting the grafted plant to drought. Some of these genes are more expressed in root tips than in more mature suberized zones of the roots where the radial hydraulic conductivity is lower Gambetta et al. This allows the plant to increase soil exploration for water uptake while reducing transpiration Sharp and Davies, ; Cramer et al. The nature of the plural forms of the second group touches upon the resources of the firms, including, but not limited to, the technological resources and the optimal scale of the plants. Osmotic adjustment helps maintaining water into the cells Plants evolved in different ways to maintain physiological activity while water potential declines.
There is a large variability among rootstocks in root vascular anatomy vessel diameter and length, percentage of conducting tissues; Pongracz and Beukman, ; Alsina et al. The distinctive feature of firms in opposition to markets is the replacement of price mechanism by hierarchy to coordinate production. The QTLs detected in the offspring included genes that have been characterized as potentially involved in water deficit responses Marguerit et al. Water extraction capacities by roots are reported to be variable between rootstocks and genetically controlled Carbonneau, ; Soar et al. A major response is osmotic adjustment, which allows the cells to maintain their water content and turgor even when water potential decreases in their vicinity.
The most appropriate theoretical matrix for reading each case would be the one that accounts for the variables that in fact influenced the choice of the governance structure. During the night, water potential equilibrates vertical line.
This question has been addressed in a 3-year experiment using a pedigree population issued from the cross between V. This is usually achieved in most vineyards but global change seriously threatens this fragile equilibrium.
Carbohydrates stored in cells neighboring the conducting vessels, together with aquaporins e. While anisohydric cultivars may be recommended in the case of short periods of moderate water deficit because they sustain production, the isohydric ones appear as more suitable to face long lasting periods of severe drought. Vessel embolism decreases stem hydraulic conductance, which in turn decreases leaf water potential itself, favoring further embolism. Differences are related to the development of suberized apoplastic barriers in the root tips at the beginning of the maturation zone. Some studies concluded to variable ranking of an isohydric behaviors between grapevine cultivars, notably Grenache and Syrah Pou et al. In grapevine, variability in ABA accumulation has been observed among rootstocks Peccoux, as well as scions Soar et al.
In some cases, maintaining plural forms inherited from the firm's past do not raise business costs weak path dependence. Besides, it was recently shown that wild Vitis species stems differ for their sensitivity to cavitation under water stress and their ability to repair after rehydration, paralleling contrasting responses of root pressure to re-watering associated to osmotic regulation Knipfer et al. The tight coupling between photosynthesis and transpiration, which are both controlled by stomata and leaf area, does not make trivial to decrease transpiration without altering photosynthesis. According to Bradach and Eccles , a plural form emerges when the same firm adopts different governance structures to conduct identical or very similar transactions.
Limited vigor under drought results in a decrease of evaporative areas, thereby lowering transpiration and releasing water tension in the xylem. In other cases, a single governance structure would be more efficient strong path dependence , but the costs of reorganization are high, making persist a suboptimal governance structure. In several species including the overall, roughly isohydric grapevine Prieto et al. The motivation for a theory of plural forms came from the realization of the existence of an intriguing diversity of hybrid arrangements.
This gaseous embolism may result in the rupture of the water column in the xylem, being a major threat for the plant. Without pretending to exhaust all possibilities, the article suggests a classification of the plural forms, hoping that it will be improved and used as an instrument to organize the empirical evidence, which is rapidly increasing. Various theoretical lenses are useful to analyze the phenomenon of plural, particularly Transaction Costs Economics, Resource Based View, and Industrial Organization, setting then the issue of the adequacy of theories to the concrete cases. Conventionally, free water at sea level has a potential of zero, corresponding to the maximal water availability in a saturated soil. In the following, we review the primary consequences of water deficit on grapevine. Further investigations of root growth properties for different rootstocks would be profitable for the future.