Carbon Dioxide and Temperature Influence Pollen Germination and Fruit Set in Cocoa

Abstract

<jats:p>The causes of poor fruit set of cocoa <jats:italic>(Theobroma cacao</jats:italic> L.) in the greenhouse were studied by examining factors that may influence pollen germination. Hand pollination of cocoa flowers resulted in 45.8% fruit set when flowers were pollinated within 3 hours of anthesis. Pollen germination did not occur until about 6 hours after pollination. Later pollinations (7 to 9 hours after anthesis) or earlier pollinations (16 to 18 hours before anthesis) did not lead to fruit set. Cocoa pollen did not germinate in vitro unless the excised flowers were incubated for 6 hours at 25C in closed vials. During the incubation period, CO<jats:sub>2</jats:sub>accumulated to a final concentration of about 85 ml·liter<jats:sup>-1</jats:sup> as a result of respiration. Ethylene production was not detectable. Incubation of flowers with a NaOH-saturated wick, to absorb CO<jats:sub>2</jats:sub>, prevented pollen germination in vitro. Incubation of flowers at 15C also prevented pollen germination in vitro at 25C. Hand pollination of flowers 7 to 9 hours after anthesis or 16 to 18 hours before anthesis using CO<jats:sub>2</jats:sub>-incubated pollen resulted in about 10% fruit set. Enclosed pollinations in vivo, in which CO<jats:sub>2</jats:sub> was allowed to accumulate, resulted in nearly 100% fruit set. The initial failure to set fruit from hand pollinations may result from poor or slow pollen germination. Moreover, CO,-incubated pollen might be used to increase fruit set in cocoa by extending the effective pollination period.</jats:p>

Fructokinase and Hexokinase from Pollen Grains of Bell Pepper (Capsicum annuum L.): Possible Role in Pollen Germination under Conditions of High Temperature and CO2 Enrichment

“…It has been suggested that these two environmental factors act via their in¯uence on photosynthesis and on sugar supply to the developinḡ owers (Aloni et al, 2001). Aneja et al (1992) found that CO 2 and temperature had direct effects on pollen germination in cocoa. We have previously shown that high temperature and CO 2 enrichment caused a decrease and an increase, respectively, in pepper pollen acid invertase activity, but the enzyme speci®c activity was not changed (Aloni et al, 2001).…”

Auxin modification of the incompatibility response in Theobroma cacao

“…Thus, Theobroma may represent an example of an ovarian SI system, unlike the majority of SI plants (deNettancourt 1977). Recent studies of Theobroma (Aneja et al 1992, 1994; Baker et al 1997) suggest that flower abscission because of incompatible pollination is initiated prior to the pollen tubes reaching the ovules. Aneja et al (1992, 1994) found that pollen grains of the self‐incompatible clone IMC 30 did not germinate in low pCO 2 and that elevated CO 2 could overcome SI in self‐pollinated flowers.…”

“…Recent studies of Theobroma (Aneja et al 1992, 1994; Baker et al 1997) suggest that flower abscission because of incompatible pollination is initiated prior to the pollen tubes reaching the ovules. Aneja et al (1992, 1994) found that pollen grains of the self‐incompatible clone IMC 30 did not germinate in low pCO 2 and that elevated CO 2 could overcome SI in self‐pollinated flowers. The large number of Theobroma clones prompted Warren (1994) and Warren and Sunita (1995) to search for predictors of SI .…”

Inter-species functional compatibility of the Theobroma cacao and Arabidopsis FT orthologs: 90 million years of functional conservation of meristem identity genes

“…Post selection, T1 plants were transferred to soil and grown in 16/8 day/night conditions. Plants were phenotyped for time of flowering and architectural traits as previously described [ 69 ].…”