Ecophysiology of tea

Abstract

Tea [Camellia sinensis (L.) O. Kuntze] is one of the most important beverage crops in the world. The major tea-growing regions of the world are South-East Asia and Eastern Africa where it is grown across a wide range of altitudes up to 2200 m a.s.l.. This paper reviews the key physiological processes responsible for yield determination of tea and discusses how these processes are influenced by genotypic and environmental factors. Yield formation of tea is discussed in terms of assimilate supply through photosynthesis and formation of harvestable sinks (i.e. shoots). The photosynthetic apparatus and partial processes (i.e. light capture, electron transport and carboxylation) of tea show specific adaptations to shade. Consequently, maximum light-saturated photosynthetic rates of tea are below the average for C 3 plants and photoinhibition occurs at high light intensities. These processes restrict the source capacity of tea. Tea yields are sink-limited as well because shoots are harvested before their maximum biomass is reached in order to maintain quality characters of made tea. In the absence of water deficits, rates of shoot initiation and extension are determined by air temperature and saturation vapour pressure deficit, with the former having positive and the latter having negative relationships with the above rates. During dry periods, when the soil water deficit exceeds a genotypically-and environmentally-determined threshold, rates of shoot initiation and extension are reduced with decreasing shoot water potential. Tea yields respond significantly to irrigation, a promising option to increase productivity during dry periods, which are experienced in many tea-growing regions. Key words: climate change, photoinhibition, photosynthesis, shoot growth, temperature, vapour pressure deficit, water potential † All authors have contributed equally to this articleEcofisiologia do chá: O chá [Camellia sinensis (L.) O. Kuntze] é uma das mais importantes culturas para a produção de bebidas no mundo. As principais regiões de cultivo dessa espécie se concentram no sudeste da Ásia e na África oriental, onde é cultivado numa ampla faixa de altitudes, até 2200 m acima do nível do mar. Neste artigo, revisam-se processos fisiológicos centrais determinantes da produção do chá e se discutem como esses processos são influenciados por fatores genotípicos e ambientes. A produção do chá é discutida em termos de suprimento de assimilados provenientes da fotossíntese e formação de drenos (ramos) removidos na colheita. A maquinaria fotossintética e processos parciais (i.e. captura de luz, transporte de elétrons e carboxilação) da fotossíntese, em plantas de chá, exibem adaptações à sombra. Conseqüentemente, as taxas máximas de fotossíntese saturadas à luz são inferiores às da media de plantas C 3 , observando-se também fotoinibição sob altas irradiâncias. Esses processos restringem a capacidade da fonte em plantas de chá. A produção do chá é limitada pelo dreno conquanto os ramos são colhidos antes de atingirem sua biomassa máxima, o q...

Comparison of Tolerant Ability of Mature Field Grown Tea (<i>Camellia sinensis</i> L.) Cultivars Exposed to a Drought Stress in Passara Area

“…De Costa et al (2007) also confirmed greater stomatal densities of the drought susceptible genotypes. However, Chaves (1991) showed that the physiological control of stomatal aperture is more important than the size and frequency of stomata to determine stomatal conductance under water stress.…”

Yield decline in mechanically harvested clonal tea (Camellia sinensis (L) O. Kuntze) as influenced by changes in source/sink and radiation interception dynamics in the canopy

“…PAR in the chamber was set at a saturating light intensity of 1000 µmol m -2 s -1 (De Costa et al, 2007;2009;Lin et al, 2014;Smith et al, 1993;1994), humidity was maintained above 50 %, to avoid stomatal closure, and leaf temperature was maintained between 28 and 30°C. The CO 2 concentration was adjusted to 400 µmol CO 2 mol -1 with a CO 2 mixer and the air flow was kept constant at 500 µmol s Measurements were performed soon after plucking (0 day), and then 5 and 10 days after plucking at each marked position.…”

“…In tea, the low yields associated with mechanical harvesting are believed to be compounded by the fact that tea has inherently low productivity (500 -2500 kg ha -1 year -1 of harvested plucked young shoots), which can be partly attributed to harvesting removing much of the active productive leaf area and nutrients (Mohotti & Lawlor, 2002). This is further compounded by inadequate assimilate production (source limitation), as the rates of photosynthesis are low (2-14 µmol m -2 s -1 ) compared to most C3 plants (De Costa et al, 2007;Mohotti et al, 2000;Mohotti & Lawlor, 2002). According to Manivel & Hussain (1982b), plucking results in considerable depletion of dry matter produced by the maintenance leaves in the canopy.…”

“…According to Manivel & Hussain (1982b), plucking results in considerable depletion of dry matter produced by the maintenance leaves in the canopy. In addition, as tea is thought to have originated as an understory plant in tropical rainforests, it is likely that the photosynthetic apparatus is adapted to function optimally under shade (De Costa et al, 2007) and photosynthesis may be reduced under high light intensities as a result of photoinhibition (Mohotti & Lawlor, 2002).…”

“…Tea yields may also be sink-limited due to the continual removal of shoots before they obtain a maximum biomass, which is required to maintain quality characters of made tea (De Costa et al, 2007). Tea bushes may therefore have an inadequate number of growing shoots to use photo-assimilates produced by photosynthesis (Mohotti & Lawlor, 2002;Squire, 1977;Tanton, 1979).…”