Flowering, pollination, and fruit setting in tomatoes

Transcription

1 Flowering, pollination, and fruit setting in tomatoes Literature study commissioned by Koppert Biological Systems. Jan Janse Wageningen UR Greenhouse Horticulture Wageningen, February 2017 Report GTB-5142

2 Report details Report GTB-5142 Project number: Disclaimer 2016 (institute within the legal person Wageningen Research Foundation), Postbus 20, 2665 MV Bleiswijk, Violierenweg 1, 2665 MV Bleiswijk, T , F , E glastuinbouw@wur.nl, Wageningen Plant Research. Wageningen Research Foundation accepts no liability for any damages resulting from the use of the results of this study or the application of the recommendations. Address Postbus 20, 2665 ZG Bleiswijk Violierenweg 1, 2665 MV Bleiswijk T +31 (0) F +31 (0)

3 Contents Summary 5 1 Introduction 6 2 Flower development and flowering Flower Flower cluster Reproductive organs 8 3 Pollen formation Assimilates deficit High-temperature effects Varieties and high temperatures Low-temperature effects 13 4 Ovule production 14 5 Pollination Pollination by bumblebees Release of pollen and pollination 15 6 Pollen germination 17 7 Pollen tube growth 18 8 Fertilization High and low temperatures 19 9 Fruit growth Number of seeds and fruit size Number of seeds and fruit quality Flower abnormalities Undeveloped flowers Flower abortion Undeveloped flowers High temperature Water supply and salt stress Ethylene Growth stagnation Virus infection Predatory bugs Continuous lighting Excessively long style and other abnormalities Fruit abnormalities Literature 28

4 Summary The whole process of fruit setting in tomatoes may be divided into various subsidiary processes, namely pollen formation, ovule production, pollination, pollen germination, pollen tube growth, fertilization, and fruit growth. Based on a literature study, the author has examined which factors affect the various subsidiary processes and deformations in flowers. The tomato is a self-pollinator and has hermaphrodite flowers. In order to achieve good production and quality, good pollination and fruit formation are very important. Unfortunately, for all kinds of reasons, these processes do not always proceed optimally. In many cases, a shortage of assimilates is the cause. This can particularly occur in low light conditions and/or at high temperatures and a low CO2 level. The formation of pollen grains is a more sensitive process in this regard than the development of the ovules. In particular, reduction division (meiosis), which takes place about nine days before flowering, and the period up to five days before flowering, are sensitive periods. High temperatures, for example several hours at 40 o C or temperatures above 25 o C for 24 hours, can greatly disrupt the development process of pollen grains. Effects of high temperatures include: formation of a low number of pollen grains, poor vitality of the pollen formed, the loculi remaining closed so that pollen grains are not released, long styles, and poor germination. In susceptible varieties, at prolonged high temperatures there may even be distortion to the stamens, resulting in zero fruit set. Varieties clearly differ in their sensitivity to heat stress. 24-hour temperatures below 10 o C to 13 o C also cause poor pollen quality. Report GTB- 5 The ovules are especially sensitive to high temperatures seven to five days before flowering, as well as one to three days after fertilization. They can still die at that point. As a result of vibration, for example caused by bumblebees, the pollen is released from the stamens and, ideally, ends up on the sticky stigma. A long style caused by low light or high temperatures is negative for pollination. At a higher temperature, germination, i.e. the emergence of the pollen tube from the pollen grains, takes place more quickly: at 10 o C and 35 o C, it was 5 and 0.7 hours, respectively. The number of germinating pollen grains depends on their vitality. The time required for fertilization also depends on the temperature: at 10 o C and 35 o C, it was 34 and 7.5 hours, respectively. Fruit setting proceeds optimally at a 24-hour temperature of approximately o C. The cause of flower abortion may be a shortage of assimilates (incorrect light/temperature ratio). This occurs with undeveloped flowers, for example. It can also be caused by growth stagnation, salt stress, ethylene, viruses, and an excessive number of predatory bugs.

5 Postbus ZG Bleiswijk Violierenweg MV Bleiswijk T +31 (0) F +31 (0) Rapport GTB-5142 The mission of Wageningen University & Research is 'To explore the potential of nature to improve the quality of life'. Wageningen University and specialized research institutes of Wageningen Research Foundation join forces within Wageningen University & Research to work towards resolving major challenges in terms of healthy food and living environment. With approximately 30 locations, 5,000 employees and 10,000 students, Wageningen University & Research is one of the leading organizations in its domain worldwide. An integral approach to these challenges coupled with multidisciplinary cooperation are at the core of Wageningen's unique working method.