Water relations of cotton flower petals and fruit

Abstract

Water needed for expansion is believed to enter plant tissue in response to a growth-induced water potential gradient that occurs as turgor is reduced during relaxation of cell walls or in response to increased solutes. Under water stress, the cotton flower petal continues to expand when all leaves on the plant are wilted and new leaf expansion has ceased in the shoot tips. This study was undertaken to determine if water for expansion entered the petal in response to a gradient or to increased solutes. Water potentials of cotton petal, leaf, bract and fruit were determined pre-dawn and midday in dryland and irrigated field plots. The mechanism by which petal expansion occurs appears not to be associated with a growth-induced water potential gradient or to increased solutes because the gradient is reversed from that needed to drive expansion. The water potential of the petal tissues was consistently higher than that of the subtending leaves and bracts both during and after anthesis, and under different water stress conditions. How this reversal in water potential gradient is established and maintained should provide insight into mechanisms involved in growth during water stress.

Giant Flowers of Southern Magnolia Are Hydrated by the Xylem

“…A major line of evidence for this comes from differences in water potential (C) and water content (WC) between flowers and the subtending leaves. Flowers of cotton (Gossypium hirsutum) and several dry tropical forest tree species showed C values 0.5 to 1.0 MPa less negative than leaves during transpiring conditions (Trolinder et al, 1993;Chapotin et al, 2003). If flowers were connected to the stem xylem, then transpiring leaves also connected to the stem xylem and operating at lower C should have drained flowers of their water.…”

“…Nonetheless, the few available studies suggest that flowers, unlike leaves, are hydrated by the phloem (Trolinder et al, 1993;Chapotin et al, 2003;De la Barrera and Nobel, 2004;Galen, 2005). A major line of evidence for this comes from differences in water potential (C) and water content (WC) between flowers and the subtending leaves.…”

“…A prime example of where whole plant integration of reproduction is essential concerns how flowers are supplied with the resources necessary for reproduction (Trolinder et al, 1993;Galen, 2005). Like all multicellular plant structures existing in a diffusioninadequate world, flowers from bud to bloom require continuous supplies of carbohydrates, nutrients, and water that are supplied by long-distance transport vascular systems (Trolinder et al, 1993;Chapotin et al, 2003;De la Barrera and Nobel, 2004;Galen, 2005).…”

“…Like all multicellular plant structures existing in a diffusioninadequate world, flowers from bud to bloom require continuous supplies of carbohydrates, nutrients, and water that are supplied by long-distance transport vascular systems (Trolinder et al, 1993;Chapotin et al, 2003;De la Barrera and Nobel, 2004;Galen, 2005). In particular, flowers can be water-hungry structures (Blanke and Lovatt, 1993;Galen et al, 1993;Galen, 2005), and a flower's hydraulic needs increase during anthesis due to nectar secretion and when the unfurled perianth, stamens, and stigmatic surfaces become exposed to an evaporative atmosphere (Patino and Grace, 2002;De la Barrera and Nobel, 2004;Galen, 2005).…”

Plant water status and hydraulic conductance during flowering in the southern California coastal sage shrub Salvia mellifera (Lamiaceae)

“…Vapor pressure defi cit was calculated as the difference between saturated and actual air vapor pressure at a given temperature based on air temperature and relative humidity measurements ( Rosenberg et al, 1983 ). Windt et al, 2009 ), the phloem in others ( Trolinder et al, 1993 ;Chapotin et al, 2003 ;Mingo et al, 2003 ;de la Barrera and Nobel, 2004 ), and a combination of the two in others, with the proportion changing between anthesis and fruit development ( Ho et al, 1987 ;van Ieperen et al, 2003 ). Furthermore, although the petals of some species have stomata ( Lipayeva, 1989 ;Galen et al, 1993 ;Vemmos and Goldwin, 1993 ;van Doorn, 1997 ), these stomata appear to be nonfunctional and, thus, do not contribute to the control of water loss ( Watson, 1962 ;Hew et al, 1980 ;van Doorn, 1997 ;Pati ñ o and Grace, 2002 ).…”