Water deficits at anthesis reduce CO2 assimilation and yield of lychee (Litchi chinensis Sonn.) trees

Abstract

Ten-year-old 'Tai So' lychee (Litchi chinensis Sonn.) trees growing on a sandy loam soil in subtropical South Africa (latitude 25 degrees S) were watered weekly (well-watered treatment) or droughted from late July until January (drought treatment). After 16 weeks, at which time the trees obtained most of their water from below 150 cm, average soil water content at 0 to 150 cm depth was 14.5 +/- 0.1% in the well-watered treatment and reached a minimum of 7.6% in the drought treatment. At Week 7, minimum leaf water potential (Psi(L)) in the morning and early afternoon declined to -2.6 and -2.8 MPa, respectively, in droughted trees compared with -1.5 and -2.2 MPa, respectively, in well-watered trees. From Week 9, stomatal conductance and net CO(2) assimilation rate ranged from 70 to 300 mmol m(-2) s(-1) and 3 to 13 micro mol CO(2) m(-2) s(-1), respectively, in well-watered trees. The corresponding values for droughted trees were 50 to 180 mmol m(-2) s(-1) and 2 to 6 micro mol CO(2) m(-2) s(-1). Five weeks after rewatering the droughted trees, gas exchange had not recovered to the rate in well-watered trees, although tree water status recovered within a week of rewatering. In the well-watered trees, water use (E(t)) was 26 +/- 1 mm week(-1) with evaporation (E(p)) of 20 to 70 mm week(-1) indicating a crop factor (k(c) = E(t)/E(p)) of 0.4 to 1.2. Before anthesis, tree water status did not affect extension growth of floral panicles or leafy shoots. In contrast, no vegetative shoots were initiated after fruit set in the droughted trees when Psi(L) in the morning declined to -2.5 MPa. Water deficits reduced initial fruit set by 30% and final fruit set by 70% as a result of fruit splitting (41.2 +/- 4.0% versus 10.0 +/- 1.3%). Water deficits did not alter the sigmoidal pattern of fruit growth, but reduced yield from 51.4 +/- 5.5 kg tree(-1) in well-watered trees to 7.4 +/- 3.3 kg tree(-1) in droughted trees.

Lychee tree parameters for water balance modeling

“…Finally, further possible K c values are computable if the variability of the K e,max value is additionally accounted for. Hence, the results are in accordance with Menzel et al (1995), who reported a K c value range between 0.4 and 1.2. The suggested K c value of Bredell (1971) (K c =0.85) would mean a K cb of 0.8 (for dry soil surfaces with K e =0.05) and ties in with the recommendation in this study to set K cb equal to 0.8.…”

“…Root distribution of lychee trees has only been reported in acid soils of a subtropical region (Menzel et al, 1990). Bredell (1971) suggested using a general crop coefficient (K c ) to calculate the potential evapotranspiration (ET pot ) of lychee trees whereas Menzel et al (1995) published a K c value range. Finally, no data was found on lychee tree interception and evaporation underneath the tree canopies.…”

Calcio y ácido giberélico en el bretado de frutos de litchi (Litchi chinensis Soon.) cultivar Mauritius

“…In this regard, experiments in India, Africa and Australia indicated that periods of drought can have different effects on yield, quality and cracking depending on the level and period of water deficit. In South África, a water deficit during fruit development increased the number of cracked or rippened fruits (41%) in relation to fruits harvested from trees with good irrigation (10%) (Menzel et al, 1995). Abbott et al (1986) showed reduction of cracking problems in tomato fruits, by increasing irrigation frequencies.…”

“…Al respecto, experimentos en la India, África y Australia indicaron que periodos de sequía pueden tener diferentes efectos en el rendimiento, calidad y bretado dependiendo del nivel y periodo de déficit hídrico. En Sudáfrica, un déficit hídrico durante el desarrollo del fruto incrementó la cantidad de frutos rajados o bretados (41%) en relación a frutos cosechados de árboles con buen riego (10%) (Menzel et al, 1995). Abbott et al (1986) reportaron reducción de problemas de bretado en frutos de tomate, mediante el incremento de frecuencias riego.…”

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF LYCHEE (LITCHI CHINENSIS SONN.): A REVIEW

“…In a related experiment in South Africa, water was withheld from trees from just before emergence of the inflorescences until four weeks after harvest (Menzel et al ., 1995). Water deficits reduced initial fruit set from 21.0±1.1fruit in an inflorescence to 14.1±1.8 fruit, and also the final set at harvest from 7.0±0.3 to 2.0±0.5 fruit.…”