The life cycle of higher plants varies greatly, depending on the species. In small herbaceous plants such as Arabidopsis thaliana, the cycle from seed to seed is 6 weeks, whereas woody plants with a long juvenile phase may not start flowering for several decades. Hence, most of the information on reproduction in plants is obtained from herbaceous models using Arabidopsis thaliana (Boss et al., 2004
; Jack, 2004), Nicotiana tabacum or similar species (Rieu et al., 2003).
There is rich interest in the reproductive physiology of woody plants. For example, it has been shown that there is a strong relationship between flower development and carbohydrates (Rodrigo et al., 2000; Jean and Lapointe, 2001; Ruiz et al., 2001; Iglesias et al., 2003). In particular, the concentration of starch in the ovule at specific steps of development is closely correlated to fertility. In Prunus armeniaca, secondary ovules that degenerate often display starch degradation in their tissues (Rodrigo and Herrero, 1998). Moreover, carbohydrate physiology in flowers is affected by environmental stresses such as drought (Lalonde et al., 1997), chilling (Ebadi et al., 1995) or heat (Young et al., 2004), which lead to partial or total sterility.
In Vitis vinifera L., the pathways of inflorescence and flower development contrast with those for many other species in several aspects (Boss et al., 2003), with stresses delaying or stopping reproductive development. For example, low temperatures near flowering affect ovule development and pollen tube growth (Ebadi et al., 1995). These responses are mediated by perturbations in carbohydrate physiology. Indeed, shading the leaves reduces photosynthesis and carbohydrate supply to the developing inflorescences, causing flower abscission and lower yields (Jackson, 1991). The reaction to stresses differs according to the genotypes (Gu et al., 1996; Zapata et al., 2004). ‘Gewurztraminer’ and ‘Pinot Noir’ have different rates of flower abscission, related to the sugar content in the inflorescence during flower development (Lebon et al., 2004). Efforts to understand this behaviour would be improved by developing a reliable model of flowering and carbohydrate physiology.
Grapevine cuttings can flower when grown under controlled conditions (Mullins, 1966; Mullins and Rajasekaran, 1981), although the available protocols are complicated. Moreover, the correspondence between the development of inflorescences in vitro and in the vineyard is not well explained. The objective of this work was to provide a simple protocol for flowering in in vitro cuttings that mimic sexual reproduction in the field. The development of male and female tissues and the presence of starch within the flowers were followed during ontogenesis in cuttings and the response compared in vineyards. The study was performed in ‘Gewurztraminer’ and ‘Pinot Noir’, which differ in fertility and sensitivity to flower abscission (Lebon et al., 2004).
Answers to all your Biology Questions
