PHYSIOLOGICAL BASIS OF YIELD VARIATION OF TEA (CAMELLIA SINENSIS) DURING DIFFERENT YEARS OF THE PRUNING CYCLE IN THE CENTRAL HIGHLANDS OF SRI LANKA

Abstract

The objective of this study was to elucidate the physiological basis of the significant yield decline that occurs during the fourth year of the pruning cycle of tea. Biomass partitioning, which was hypothesized to be a major factor in causing this yield decline, was measured by destructive harvests of entire tea bushes, in two contrasting, mature, field-grown tea cultivars (TRI 2025 and DT1) at the end of different years of the pruning cycle. In both cultivars, yield showed continuous increases from year 1 to 3, followed by reductions of 44% and 35% in TRI2025 and DT1 respectively in the fourth year. Patterns of biomass partitioning to roots, stems or branches did not correlate with the above yield variation whereas harvest index, canopy leaf area index and mature leaf dry weight showed variations which paralleled the yield variation. The fourth-year decline in harvest index was brought about by reductions in both shoot number per m 2 and mean individual shoot weight, which indicate a reduction in sink strength. Both cultivars showed reductions in light-saturated photosynthetic rate of maintenance foliage during the second half of the pruning cycle, indicating reduced source capacity. Hence, a combined reduction of both sink strength and source capacity during the fourth year could have brought about the significant yield reduction in tea. A significant increase of root starch in the fourth year indicated a down-regulation of physiological activities of the bush towards the end of the pruning cycle. Mechanisms responsible for this down-regulation need to be elucidated by further research.

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

“…The overall decline in yield observed in mechanically harvested tea was therefore a result of a combination of reduced number and dry mass of the most desirable shoots. This is in agreement with a study on yield decline over the pruning cycle in Sri Lanka, where the decline in yield was paralleled with changes in canopy leaf area index and mature leaf dry mass (De Costa et al, 2009).…”

“…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.…”

Characterization of Young Shoot Population, Yield, and Nitrogen Demands of Tea (Camellia sinensis L.) Harvested under Different Standards

“…The biomass of the whole plant in the present study (60.2-65.2 t/ha, Table 3) was comparable to results found in tea agroforestry in Assam, India [33], but much lower for tea plantations in Kenya (91-155 t/ha) [34] and Sri Lanka (81-90 t/ha) [31]. Nevertheless, the proportions of root dry matter were much higher in the present study (27.3-41.5%) than in previous studies (10-15% in [34], 13-16% in [31]). This difference may be related to different varieties, ages, spacing of plants, and growth conditions [33][34][35][36].…”

“…Nevertheless, the shoot density was still high and there was a highly significant negative correlation between the weight per shoot and shoot density. These findings suggest that the provision of photo-assimilates to support the growth of young shoots might have been limited as the result of an excessively intensive harvest, leading to insufficient maintenance foliage in the canopy and limited photosynthetic capacity [31,32]. The canopy activity was rejuvenated and the sink-source relation was improved by a deep pruning after the spring tea season in April in year 2, resulting in larger shoot weights the following summer and autumn.…”

The Effect of Pyraclostrobin Application on Yield of Tea (Camelia sinensis (L.) O. Kuntze) under Wet Season

“…The weight per shoot was obtained by the capability of source in distributing photo-assimilate and bud initiation to sink (De Costa et al, 2009). Table 4 presented that the pecco weight treated with pyraclostrobin was not significantly different compared to control.…”