Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.

Evolution of floral display in eichhornia paniculata (pontederiaceae): direct and correlated responses to selection on flower size and number

Abstract: Trade-offs between flower size and number seem likely to influence the evolution of floral display and are an important assumption of several theoretical models. We assessed floral trade-offs by imposing two generations of selection on flower size and number in a greenhouse population of bee-pollinated Eichhornia paniculata. We established a control line and two replicate selection lines of 100 plants each for large flowers (S+), small flowers (S-), and many flowers per inflorescence (N+). We compared realized heritabilities and genetic correlations with estimates based on restricted-maximum-likelihood (REML) analysis of pedigrees. Responses to selection confirmed REML heritability estimates (flower size, h2 = 0.48; daily flower number, h2 = 0.10; total flower number, h2 = 0.23). Differences in nectar, pollen, and ovule production between S+ and S- lines supported an overall divergence in investment per flower. Both realized and REML estimates of the genetic correlation between daily and total flower number were r = 1.0. However, correlated responses to selection were inconsistent in their support of a trade-off. In both S- lines, correlated increases in flower number indicated a genetic correlation of r = -0.6 between flower size and number. In contrast, correlated responses in N+ and S+ lines were not significant, although flower size decreased in one N+ line. In addition, REML estimates of genetic correlations between flower size and number were positive, and did not differ from zero when variation in leaf area and age at first flowering were taken into account. These results likely reflect the combined effects of variation in genes controlling the resources available for flowering and genes with opposing effects on flower size and number. Our results suggest that the short-term evolution of floral display is not necessarily constrained by trade-offs between flower size and number, as is often assumed.

Early stomatal closure in waterlogged pea plants is mediated by abscisic acid in the absence of foliar water deficits

Abstract: Soil waterlogging decreased leaf conductance (interpreted as stomatal closure) of vegetative pea plants (Pisuin sativum L cv ‘Sprite’) approximately 24 h after the start of flooding, ie from the beginning of the second 16 h-long photo-period Both adaxial and abaxial surfaces of leaves of various ages and the stipules were affected Stomatal closure was sustained for at least 3 d with no decrease in foliar hydration measured as water content per unit area, leaf water potential or leaf water saturation deficit Instead, leaves became increasingly hydrated in association with slower transpiration These changes in the waterlogged plants over 3 d were accompanied by up to 10-fold increases in the concentration of endogenous abscisic acid (ABA) Waterlogging also increased foliar hydration and ABA concentrations in the dark Leaves detached from non-waterlogged plants and maintained in vials of water for up to 3 d behaved in a similar way to leaves on flooded plants, ie stomata closed in the absence of a water deficit but in association with increased ABA content Applying ABA through the transpiration stream to freshly detached leaflets partially closed stomata within 15 min The extractable concentrations of ABA associated with this closure were similar to those found in flooded plants When an ABA-deficient ‘wilty’ mutant of pea was waterlogged, the extent of stomatal closure was less pronounced than that in ordinary non-mutant plants, and the associated increase in foliar ABA was correspondingly smaller Similarly, waterlogging closed stomata of tomato plants within 24 h, but no such closure was seen in ‘flacca’, a corresponding ABA-deficient mutant The results provide an example of stomatal closure brought about by stress in the root environment in the absence of water deficiency The correlative factor operating between the roots and shoots appeared to be an inhibition of ABA transport out of the shoots of flooded plants, causing the hormone to accumulate in the leaves

Supplemental manganese improves the relative growth, net assimilation and photosynthetic rates of salt-stressed barley

Abstract: Previous results in our laboratory indicated that a reduced Mn concentration in the leaves of barley was highly correlated with the reduced relative growth and net assimilation rates of salt-stressed plants. If Mn deficiency limits the growth of salt-stressed barley, then increasing leaf Mn concentrations should increase growth. In the present study, the effect of supplemental Mn on the growth of salt-stressed barley (Hordeum vulgare L. cv. CM 72) was tested to determine if a salinity-induced Mn deficiency was limiting growth. Plants were salinized with 125 mol m−3 NaCl and 9.6 mol m−3 CaCl2. Supplemental Mn was applied in 2 ways: 1) by increasing the Mn concentration in the solution culture and 2) by spraying Mn solutions directly onto the leaves. Growth was markedly inhibited at this salinity level. Dry matter production was increased 100% in salt-stressed plants treated with supplemental Mn to about 32% of the level of nonsalinized controls. The optimum solution culture concentration was 2.0 mmol m−3, and the optimum concentration applied to the leaves was 5.0 mol m−3. Supplemental Mn did not affect the growth of control plants. Further experiments showed that supplemental Mn increased Mn concentrations and uptake to the shoot. Supplemental Mn increased the relative growth rate of salt-stressed plants and this increase was attributed to an increase in the net assimilation rate; there were no significant effects on the leaf area ratio. Supplemental Mn also increased the net photosynthetic rate of salt-stressed plants. The data support the hypothesis that salinity induced a Mn deficiency in the shoot, which partially reduced photosynthetic rates and growth.