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  • Author or Editor: J.W. Daniell x
  • Journal of the American Society for Horticultural Science x
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Abstract

Greenhouse-grown peach [Prunus persica (L.) Batsch] seedlings and cuttings were drought-stressed by reducing soil water potential (ψsoil) from field capacity (FC) to permanent wilting point, (PWP). Mean ψsoil and leaf water potential (ψleaf) were correlated with measurements of stomatal conductance (gs), net photosynthetic (Pn) rate, and vapor pressure deficit (VPD). Decreasing Pn and gs trends were noted as ψsoil decreased. Photosynthetic rate and gs were significantly reduced at ψleaf more negative than −1.5 MPa. Values of Pn and gs were more highly correlated to ψleaf than ψsoil. A midday depression in Pn rates began 2 hr earlier and peak rates were at least 50% lower when ψsoil was more negative than −0.05 MPa. The correlation coefficient (r) between ψleaf and ψsoil and between gs and Pn rate at different ψsoil was above 0.70. The r values decreased as soil and plant water potential became more negative. Stomatal conductance peaked at optimal ψsoil (FC) 2 hr following sunrise. Photosynthetic rate peaked at a ψsoil around −0.05 MPa 4 hr after sunrise.

Open Access

Abstract

A growth equation and a yield relationship were calculated to estimate space requirements and yields of two pecan cultivars (Carya illinoensis (Wangenh.) C. Koch]. The resulting estimates were used with pruning cost estimates in a simulation model to determine the orchard space management practice that maximizes income over time. The income maximizing spacings were 10.7 × 10.7 m and 13.7 × 13.7 m for the precocious ‘Desirable’ and the non-precocious ‘Stuart’, respectively. Annual pruning after the canopy closed produced the highest income for both cultivars.

Open Access