Bussières Philippe
Unité de recherche sur les Plantes et Systèmes de culture Horticoles, Institut National de la Recherche Agronomique, 84914 Avignon Cedex 9, France. Email:
Funct Plant Biol. 2002 May;29(5):631-641. doi: 10.1071/PP00144.
Approximately 3 weeks after pollination, the water import rate per unit tomato fruit area generally decreases linearly with fruit radius. In order to explain why, in the first 3 weeks, the water import rate of the fruit is lower than predicted by this regression, a model of water flow through the pedicel and a model of water import based on the potential of water entering the fruit and calyx transpiration were formulated. Using data sets available in the literature, these models predict a water potential drop along the pedicel that decreases sharply during the first 3 weeks, while the calculated hydraulic conductivity of the pedicel phloem, which is presumed to be the main pathway of the water imported in the tomato fruit, increases sharply in the lower range of values known for plant phloem conductivity. These models also predict an increase in water import into young fruit when calyx transpiration is decreased, which is consistent with data from the literature. In order to explain the increasing pedicel phloem conductivity, a model of water flow in the pedicel sieve tubes was formulated based on the literature data for the fruit stalk of Lupinus albus. It was suggested that the conductivity might increase because of the development of pores in the sieve plates. Using this hypothesis, the increase in pore radius values within an acceptable range was calculated. This study shows that, under a wide range of conditions, water import in young tomato fruit is limited by the low potential of the water entering the fruit due to pedicel resistance and calyx transpiration. It provides a model to predict young tomato fruit expansion and a testable hypothesis, which can be checked by measuring the size of the phloem component in the fruit pedicel.
授粉后约3周，单位番茄果实面积的水分输入率通常随果实半径呈线性下降。为了解释为何在最初3周内，果实的水分输入率低于该回归预测值，构建了一个通过果柄的水流模型以及一个基于进入果实的水势和花萼蒸腾作用的水分输入模型。利用文献中可得的数据集，这些模型预测果柄沿线的水势下降在最初3周内急剧降低，而假定为番茄果实水分输入主要途径的果柄韧皮部的计算水力传导率，在植物韧皮部传导率已知的较低值范围内急剧增加。这些模型还预测，当花萼蒸腾作用降低时，幼果的水分输入会增加，这与文献数据一致。为了解释果柄韧皮部传导率的增加，基于白羽扇豆果柄的文献数据构建了一个果柄筛管内水流模型。有人提出，传导率可能因筛板上孔隙的形成而增加。利用这一假设，计算了在可接受范围内孔隙半径值的增加情况。本研究表明，在广泛的条件下，幼番茄果实的水分输入受到因果柄阻力和花萼蒸腾作用导致进入果实的水势较低的限制。它提供了一个预测幼番茄果实膨大的模型以及一个可检验的假设，可通过测量果实果柄中韧皮部成分的大小来进行验证。
