Intake and digestion of leaves of Quercus calliprinos, Pistacia lentiscus, and Ceratonia siliqua, with and without supplementation of various amounts of polyethylene glycol (PEG), were examined. The tannin contents in these species exerted a substantial negative effect on feed intake and digestion. The effects were species specific and related to tannin content. Once-daily Supplementation with PEG efficiently neutralized the negative effects of tannins. The amount of PEG needed to produce a maximal increase in feed intake was lower than the amount required to produce a maximal increase in digestibility. The intake of digestible crude protein and metabolizable energy was raised in PEGsupplemented animals from a submaintenance level to levels considerably exceeding the maintenance requirement of goats. The response was related to the tannin content of the plant.

1. Body weight and the weight of the digestive organs and activities of some digestive enzymes were determined from hatching to 23 d of age. 2. Relative daily growth rate peaked at 11 d of age (22% gain/d) and then decreased gradually. 3. The vitelline residue was decreased rapidly from 4.6 g at hatching to negligible values from 4 d of age. 4. Maximal allometric growth of the pancreas and small intestine was 4-fold and that of liver 2-fold greater than that of the body. 5. Activities (units/kg body weight) of the digestive enzymes measured in the pancreas and intestinal contents increased with age. In the pancreas maximal values were attained on day 8 for amylase and lipase and 11 for trypsin and chymotrypsin. In the small intestine maxima were attained on day 4 for lipase, 11 for trypsin and chymotrypsin and 17 for amylase. 6. The development of secretion of digestive enzymes in the post-hatched chick could be a limiting factor in digestion and subsequently in food intake and growth.

Plants employ stomatal closure and reduced growth to avoid water deficiency damage. Reduced levels of the growth-promoting hormone gibberellin (GA) lead to increased tolerance to water deficit, but the underlying mechanism is unknown. Here, we show that the tomato () DELLA protein PROCERA (PRO), a negative regulator of GA signaling, acts in guard cells to promote stomatal closure and reduce water loss in response to water deficiency by increasing abscisic acid (ABA) sensitivity. The loss-of-function mutant exhibited increased stomatal conductance and rapid wilting under water deficit stress. Transgenic tomato overexpressing constitutively active stable DELLA proteins (S-) displayed the opposite phenotype. The effects of S- on stomatal aperture and water loss were strongly suppressed in the ABA-deficient mutant , indicating that these effects of S- are ABA dependent. While DELLA had no effect on ABA levels, guard cell ABA responsiveness was increased in S- and reduced in plants compared with the wild type. Expressing S- under the control of a guard-cell-specific promoter was sufficient to increase stomatal sensitivity to ABA and to reduce water loss under water deficit stress but had no effect on leaf size. This result indicates that DELLA promotes stomatal closure independently of its effect on growth.

Gibberellin (GA) regulates plant development primarily by triggering the degradation/deactivation of the DELLA proteins. However, it remains unclear whether all GA responses are regulated by DELLAs. Tomato (Solanum lycopersicum) has a single DELLA gene named PROCERA (PRO), and its recessive pro allele exhibits constitutive GA activity but retains responsiveness to external GA. In the loss-of-function mutant pro DGRAS , all examined GA developmental responses were considerably enhanced relative to pro and a defect in seed desiccation tolerance was uncovered. As pro, but not pro DGRAS , elongation was promoted by GA treatment, pro may retain residual DELLA activity. In agreement with homeostatic feedback regulation of the GA biosynthetic pathway, we found that GA20oxidase1 expression was suppressed in pro DGRAS and was not affected by exogenous GA 3 . In contrast, expression of GA2oxidase4 was not affected by the elevated GA signaling in pro DGRAS but was strongly induced by exogenous GA 3 . Since a similar response was found in Arabidopsis thaliana plants with impaired activity of all five DELLA genes, we suggest that homeostatic GA responses are regulated by both DELLA-dependent and -independent pathways. Transcriptome analysis of GA-treated pro DGRAS leaves suggests that 5% of all GA-regulated genes in tomato are DELLA independent. INTRODUCTIONThe phytohormone gibberellin (GA) regulates numerous developmental processes throughout the plant life cycle, including seed germination, stem elongation, flowering, and fruit set (Yamaguchi, 2008). The signaling pathway from GA perception to transcriptional activation has been intensively studied over the past two decades and its major components have been identified. The nuclear DELLA proteins, a subgroup of the GRAS transcription factors family, suppress GA signaling (Locascio et al., 2013). GA binding to the soluble GIBBERELLIN INSENSITIVE DWARF1 (GID1) receptor triggers GID1 interaction with the DELLA proteins (Ueguchi-Tanaka et al., 2005;Nakajima et al., 2006;Griffiths et al., 2006), which then stimulates assembly of the DELLA proteins into an SCF E3 ubiquitin ligase complex via the GID2/SLEEPY1 F-box proteins. The SCF complex polyubiquitinates the DELLA proteins, targeting them for destruction by the 26S proteosome (Sasaki et al., 2003;Dill et al., 2004;Griffiths et al., 2006;Harberd et al., 2009;Hauvermale et al., 2012). GA, via GID1, can also reduce DELLA activity through a degradation-independent mechanism (Ariizumi et al., , 2013Ueguchi-Tanaka et al., 2008).Despite the central role of DELLAs in GA signaling, the mechanism underlying this regulation is not fully understood. Several studies have shown that protein-protein interactions play a major role in DELLA function. DELLAs bind to various transcription factors and proteins affecting transcription, including PHYTOCHROME-INTERACTING FACTORs (PIFs), ALCATRAZ, MYC2, JASMONATE-ZIM-DOMAIN PROTEIN9, SCARECROW LIKE3 (SCL3), and TCP transcription factors (de Lucas et al., 2008;Feng et al., 2008;Arnaud et al., 2010;Ga...