Growth Rate and Water Relations of Citrus Leaf Flushes*

Abstract

Growth rates of seasonal leaf flushes of 'Valencia' orange [Citrus sinensis (L.) Osbeck] were measured and water relations characteristics of young (new) and over-wintered (old) citrus leaves were compared. New flush leaves had lower specific leaf weights and lower midday leaf water potentials than comparably exposed old leaves. Spring and summer flush new leaves had higher osmotic potentials than old leaves. These differences became non-significant as the new leaves matured. During summer conditions, water. stressed new leaves reached zero turgor and stomatal conductance also began to decrease in them at higher leaf water potentials than in old leaves. Old leaves were capable of maintaining open stomata at lower leaf water potentials. Opened flowers and new flush leaves lost more water, on a dry weight basis, than flower buds, fruit or mature leaves. The results illustrate differences in leaf water potential and stomatal conductance which can be attributed to the maintenance of leaf turgor by decreases in leaf osmotic potentials as leaves mature. These changes in citrus leaf water relations are especially important since water stress resulting from high water loss rates of new tissues could reduce flmvering and fruit set.

Differential Response in the Water Status of Immature and Mature Fronds of the Ostrich Fern (Matteuccia struthiopteris [L.] Todaro) to a Mild Water Stress

“…The typical response is wilting in the older leaves before the younger leaves. This study and others (13,15) suggest that there may be two different responses to water stress, depending on the reproduction strategy of the species. Under water stress, plants reproducing by seed only, which include many agricultural plants, will maintain flow to the apical meristem to sustain leaf, flower, and soed production.…”

“…Catsky (5) noted that young leaves received a preferential portion of the water supply and that, under large water deficits, water was translocated from older leaves to younger leaves. Lockhart (11) suggested that this phenomenon would occur if the cells in both young and mature tissue had the same g. More recently, the reverse response, initial wilting in young leaves, has been observed in several perennial plants, tea (13), and orange and grapefruit (15 …”

“…Catsky (5) noted that young leaves received a preferential portion of the water supply and that, under large water deficits, water was translocated from older leaves to younger leaves. Lockhart (11) suggested that this phenomenon would occur if the cells in both young and mature tissue had the same g. More recently, the reverse response, initial wilting in young leaves, has been observed in several perennial plants, tea (13), and orange and grapefruit (15). In grapefruit and orange, this response was associated with a lower 4i, in the older leaves (15 Statistical analyses of the effect of mild water stress and time of day on the measured and calculated parameters were performed on the University of Guelph computer using the MEANS and ANOVA procedure in the Statistical Analysis System (SAS).…”

Evaluation of an operational real-time irrigation scheduling scheme for drip irrigated citrus fields in Picassent, Spain

“…Previous research for citrus trees suggested that the minimum water potential value at wilting point can be down to −1.7 MPa for young leaves, and −1.9 MPa to −2.6 MPa for mature leaves (Syvertsen et al, 1981;Syvertsen, 1982). It is also reported that citrus trees under regulated deficit irrigation can have a threshold stem water potential of −1.84 MPa (Ballester et al, 2014).…”

Variação sazonal da fotossíntese e relações hídricas de laranjeira 'Valência'

“…O estudo das relações hídricas é realizado a partir do monitoramento de variações na transpiração, potencial de água na folha ou ramo, condutância estomática e umidade do solo e ar (COHEN et al, 1997;KAUFMANN;HALL, 1972;KAUFMANN, 1975;LEVY, 1980;MACHADO et al, 2002MACHADO et al, , 2006SYVERTSEN, 1982;ALBRIGO, 1980a;ALLEN, 1981). Considerando um continuum de água no sistema solo-planta-atmosfera (ANGELOCCI, 2002;NOBEL, 1999), as inter-relações entre as variáveis fisiológicas e ambientais podem ser sumarizadas da seguinte forma: (a) a baixa disponibilidade de água no solo reduz a absorção de água pelas raízes, ocasionando menor hidratação da parte aérea (verificado pelos baixos valores de potencial de água na folha ou ramo).…”